Does a TBM (tunnel boring machine) headhouse need ATEX-rated motors and spark-resistant duct?

Yes, when the tunnel alignment passes through ground with methane potential or when the TBM uses compressed air intervention. AS/NZS 60079 applies to any enclosure where flammable atmosphere is reasonably foreseeable. On the Melbourne Metro Tunnel, Cross River Rail, WestConnex M4M5, Sydney Metro and similar major Australian tunnel projects, the TBM headhouse is typically Zone 2 around the launch shaft and Zone 1 at any compressed-air intervention chamber. The HVAC ductwork serving the headhouse fan plenum and the TBM grout, foam and bentonite handling areas is fabricated in 304 stainless or spark-resistant non-ferrous trim on the SBKJ SBSF-1525 Stitchwelder. The fan motors are Ex d, Ex e or Ex p certified to AS/NZS 60079 for the specific zone classification. Confined space entry to the TBM cutterhead chamber for maintenance is itself a separate AS 1746 procedure with continuous gas monitoring and rescue station provision.

Insights · Tier 1 Construction & Major Infrastructure

Tier 1 Construction Contractor & Major Infrastructure Project HVAC Ductwork Guide — Motorway, Rail, Tunnel, Wind, Solar, Hydro & LNG

A complete engineer-led HVAC ductwork specification guide for Australian Tier 1 construction contractors and the major infrastructure projects they deliver — motorway, rail, tunnel, wind farm, solar farm, hydroelectric, LNG, mining construction. Walk through the project HQ office in Sydney, Melbourne, Brisbane and Perth; the on-site project management office; the engineering and BIM office; the site induction and training room; the subcontractor compound and crib room running 24/7 shifts; the first aid and medical centre; the construction laboratory; the TBM headhouse on Melbourne Metro Tunnel and Cross River Rail; the plant maintenance shed; the crane operator cab; the welder portable shelter; the confined space rescue station; the hydrocarbon storage compound; the helipad refuelling enclosure; and the SBKJ machine configuration that fabricates the duct package to AS 1668.2, AS 4254, AS/NZS 60079 and the Department of Infrastructure federal and state standards on the first run.

By SBKJ Engineering Team · Published May 15, 2026 · 48 min read · Reviewed by SBKJ QA & Engineering

Why a Tier 1 major project compound is its own HVAC category

A modern Australian Tier 1 major infrastructure project is not a building. It is a small industrial estate that sits between a metropolitan office tower and a remote mining camp on the HVAC specification spectrum, but it borrows from both and adds elements neither carries. The CIMIC Group joint-venture compound on the Sydney Metro West tunnel works, the Lendlease and John Holland joint-venture compound at Melbourne Metro Tunnel, the John Holland and CPB and UGL PULSE compound at Cross River Rail in Brisbane, the Future Generation joint-venture compound at Snowy 2.0 in the Snowy Mountains, the Acciona and Webuild joint-venture compound at North East Link in Melbourne, the Lendlease and Acciona and Samsung joint-venture compound at Sydney Metro West — every one of these sits 12 to 36 months on a single site, houses 800 to 4,500 construction workers and engineers on a rotating roster, and operates 24/7 through the bulk of the construction window.

The compound itself is a hybrid. The senior project management team and the engineering, design, BIM and CAD team work out of an on-site project management office (PMO) building that sits somewhere between a corporate office floorplate and a transportable site office — Class 5 NCC under the National Construction Code, AS 1668.2 at 10 L/s per person, NC-35 acoustic, but built to AS 4117 portable building specification on relocatable foundations because the entire compound demobilises at project completion. The senior corporate leadership runs the project from the Tier 1 contractor's project HQ in Sydney, Melbourne, Brisbane, Perth or Adelaide — a permanent or long-lease commercial fit-out in one of the major office towers, with a dedicated war room, daily video link to the on-site PMO and a quarterly steering committee for the major project board. The subcontractor compound houses dozens of trade subcontractors — civil, electrical, mechanical, communications, geotechnical, environmental, traffic management — each with their own donga office, lunch room and storage shed, sharing the central crib room, ablution block, first aid station and induction room.

The construction face of the project introduces the elements that no office tower and no mining camp carries. The motorway construction site itself has a kilometre-by-kilometre rolling work face with temporary haul roads, dust suppression water carts, concrete batch plants, asphalt plants and aggregate stockpiles. The rail construction project has a rail formation, ballast handling, sleeper placement and overhead line installation along a 10 to 1,700 km alignment. The tunnel construction project has a TBM headhouse with the launch shaft and the tunnel ventilation main fan plenum, the segment production and casting yard, the grout and foam and bentonite handling plant, the spoil conveyor and stockpile, and the confined space entry and rescue procedure that goes with any tunnel under AS 1746. The wind farm construction project has the turbine erection cranes (giant climbing tower cranes and 1,200-tonne mobile cranes), the tower segment lay-down, the blade lay-down, the nacelle assembly area and the substation and grid connection compound. The solar farm construction project has the racking and panel installation rolling work face. The hydroelectric construction project (Snowy 2.0, Hume Dam upgrades, Marinus Link landing) has a deep underground excavation, a power station cavern and a turbine erection sequence inside the underground space. The LNG construction project has an LNG processing train assembly area and a marine module offloading interface. The mining construction camp houses the construction workforce while a new processing plant or rail line is built.

Every one of these construction faces has supporting HVAC infrastructure — crane operator cabs, welder portable shelters, plant maintenance sheds, confined space rescue stations, dewatering pit covers, hydrocarbon storage compounds, helipads — and every one of these supporting elements sits under a different NCC classification, attracts a different AS 1668.2 ventilation calculation, and uses a different duct material specification. The HVAC consultant designing the compound has to satisfy NCC Class 5 (office), Class 9a (medical), Class 9b (assembly), Class 8 (laboratory and workshop) and Class 10b (non-habitable buildings and structures) on the same site, layered with AS/NZS 60079 hazardous area classification at the genset compound and the hydrocarbon storage, AS 1940 flammable liquids storage, AS 4564 and AS 5601 LPG supply, AS 4117 portable office building construction, AS 1746 confined space monitoring, AS 1742 traffic control, AS 1530.4 fire-rated duct and AS 1851 routine service.

This guide walks through the compound building-by-building and zone-by-zone, anchors every recommendation to the relevant Australian Standard, and closes with the SBKJ machine configuration that an Australian duct contractor needs to fabricate the package on time and within the contract margin. The numbers are calibrated against what our engineers see across the Australian sector — the CIMIC, John Holland, Lendlease, Multiplex, Hutchinson, BMD, Acciona, Ferrovial, Webuild, Downer, Civmec, Monadelphous, Worley, Macmahon and NRW project portfolios, the Australian Constructors Association (ACA) member firms, and the Engineers Australia and Infrastructure Partnerships Australia industry benchmarks.

Regulatory backbone — NCC, AS 1668, AS 4117, AS/NZS 60079 and Department of Infrastructure standards

Every Australian Tier 1 contractor compound and major infrastructure project inherits the same regulatory stack regardless of project type or state. The Australian Building Codes Board administers the National Construction Code. Standards Australia maintains the AS 1668 ventilation series and the AS 4254 duct construction series. Safe Work Australia publishes the Workplace Exposure Standards for Airborne Contaminants. The state mining safety regulator (NSW Resources Regulator, Resources Safety & Health Queensland, DEMIRS in Western Australia, ETSA in South Australia and the Northern Territory equivalent) administers underlying mining and construction safety legislation. The Department of Infrastructure, Transport, Regional Development, Communications and the Arts (federal) and the state transport departments (Transport for NSW, Department of Transport and Planning VIC, Department of Transport and Main Roads QLD, Main Roads WA, Department for Infrastructure and Transport SA) administer the project-specific technical standards that overlay the national codes.

The codes and standards that matter for a Tier 1 compound HVAC ductwork specification:

NCC Volume One, classifications across the compound. Class 5 (office) for project HQ, on-site PMO, engineering and BIM office, smaller induction rooms, smaller first aid rooms. Class 6 (food premises) for any compound mess hall and amenity kitchen. Class 9a (health-care building) for first aid and medical with onsite doctor or nurse. Class 9b (assembly building) for large induction and training rooms, conference rooms, recreation rooms, subcontractor lunch rooms supplying more than 50 occupants. Class 8 (laboratory or workshop) for the construction laboratory and the plant maintenance shed. Class 10b (non-habitable buildings and structures) for the genset compound, hydrocarbon storage compound, helipad refuelling enclosure, dewatering pit cover and confined space rescue station.
AS 1668.1. The use of ventilation and air-conditioning in buildings, fire and smoke control. The smoke management baseline for the project HQ office, the on-site PMO, the larger induction rooms and any Class 9b assembly building above the NCC trigger thresholds.
AS 1668.2. Mechanical ventilation for acceptable indoor air quality. The per-occupancy outdoor air rate calculation that drives the supply ductwork sizing in every conditioned space across the compound.
AS 4254.1 and AS 4254.2. Ductwork construction specification. AS 4254.1 for flexible duct, AS 4254.2 for rigid sheet metal duct. Every supply, return and exhaust duct on the compound is fabricated to AS 4254 unless explicitly substituted with welded stainless or non-ferrous specification. See our AS 4254 Australian ductwork construction reference for the gauge, pressure class and seam construction tables.
AS 4117. Portable office buildings. The construction standard for transportable office buildings, dongas, lunch rooms, ablution blocks and crib rooms used across construction sites. AS 4117 governs the structural envelope and the integration of services including HVAC.
AS 1530.4. Methods for fire tests on building materials, components and structures — the fire-rated duct and damper specification.
AS 1851. Routine service of fire protection systems and equipment. Annual fire damper inspection and certification.
AS 1657. Fixed platforms, walkways, stairways and ladders. Applies to plant room access and rooftop equipment access in every compound building.
AS 1742. Manual of uniform traffic control devices. Applies to compound access, loading dock signage, helipad approach and any compound area where vehicles and pedestrians cross paths.
AS 1746. Confined space monitoring. Applies to TBM cutterhead chamber entry, tunnel cross-passage entry, deep shaft entry, dewatering pit entry, sewage holding tank entry and any ductwork access for cleaning above 1.2 m depth or with restricted egress.
AS 3580. Methods for sampling and analysis of ambient air. Boundary air quality monitoring for any compound adjacent to active construction with dust load as a planning condition (residential proximity, sensitive receiver, environmental impact statement commitment).
AS/NZS 60079. Explosive atmospheres. Zone classification for the genset compound, hydrocarbon storage, helipad refuelling enclosure, TBM headhouse where methane potential exists, LPG bulk tank and any battery storage above the NCC trigger threshold.
AS 1940. Storage and handling of flammable and combustible liquids. Bulk diesel for the construction plant fleet, petrol for utility vehicles, aviation fuel for the project helipad, kerosene for solvent washing.
AS 4036 and AS 4037. Boilers and pressure vessels. Applies to any temporary steam plant or hot water boiler on the compound.
AS 4564. General requirements for gas supply. LPG supply to the compound crib room kitchen, water heating and any gas-fired space heating.
AS 5601. Gas installations. The installation standard for the LPG distribution from bulk tank to consumption point.
AS 3000. Electrical installations. The wiring rules that govern every compound building and every HVAC plant room.
AS/NZS 3008. Electrical installations — selection of cables.
AS 4836. Health and safety in welding and allied processes — applies to the compound plant maintenance shed and the welder portable shelter, and to the fabrication of any stainless or welded duct on the SBSF-1525 Stitchwelder back at the duct contractor's shop.
AS 4801. Occupational health and safety management systems.
AS 4360. Risk management — superseded by AS/NZS ISO 31000 but still referenced in older site safety management plans.
AS 1428. Design for access and mobility. Disability access provisions across the compound, particularly in the project HQ, PMO, induction room, first aid and any public-facing facility.
AS 4740. Natural ventilation of buildings. Applies to the compound storage sheds and any non-habitable space relying on natural ventilation.
AS/NZS 1170.2. Structural design actions — wind actions. Applies to the rooftop equipment tie-down on every compound building, particularly in cyclonic regions (Region C and Region D) for any compound on the Queensland coast, Northern Territory or coastal Pilbara.
AS 1668.2 and ASHRAE Standard 62.1. The cross-reference standard pair. AS 1668.2 is the Australian primary standard, ASHRAE 62.1 is the international reference standard used by multinational Tier 1 operators (Acciona, Ferrovial, Webuild, BESIX, Bechtel, Samsung). Where the two diverge, design to the more stringent.
ASHRAE Standard 90.1. Energy standard for buildings except low-rise residential buildings. Reference standard for the project HQ office energy performance.
NFPA 96. Standard for ventilation control and fire protection of commercial cooking operations. Adopted in Australia as the de facto standard for kitchen grease duct construction on any compound mess hall or amenity kitchen.
Department of Infrastructure technical standards. The federal Department of Infrastructure publishes technical standards for major motorway, rail and aviation projects funded under the National Infrastructure Pipeline. The state transport departments overlay state-specific technical standards on top — Transport for NSW T HR ME 89000 series for rail mechanical, VicRoads Standard Specifications, Main Roads WA Specification, Department of Transport and Main Roads QLD Manual of Uniform Traffic Control Devices supplementary.
Engineers Australia. The peak engineering body — Code of Ethics, Continuing Professional Development obligations, Chartered Professional Engineer registration.
International Centre for Complex Project Management (ICCPM). The international reference body for complex project management practice on major projects. Reference framework for the project HQ and PMO governance structure.
Infrastructure Partnerships Australia (IPA). The industry body for public-private partnership and major project delivery in Australia. Reference framework for the contract structure and the asset handover.
Australian Constructors Association (ACA). The peak body for Tier 1 contractors. Reference framework for the workforce, safety and industrial relations standards across major projects.
Civil Contractors Federation (CCF). The peak body for civil construction. Reference framework for the civil sub-trade compound and the rolling work face.
Master Builders Australia (MBA). The peak body for building construction. Reference framework for the building sub-trade compound.
Australasian Railway Association (ARA). The peak body for rail. Reference framework for rail construction project compounds.
Roads Australia. The peak body for the road and motorway sector. Reference framework for motorway construction project compounds.
Tunnelling Forum. The peak forum for the Australian tunnelling industry, hosted by the Australasian Tunnelling Society. Reference framework for the TBM headhouse and tunnel construction compound.
Australian Industry Group (AiGroup). The peak business association for industry, including construction. Reference framework for the workforce and skills standards.

The workplace exposure standards from Safe Work Australia that drive the engineering controls inside the compound HVAC ductwork specification:

Diesel particulate matter (EC). 0.1 mg/m³ as an 8-hour time-weighted average. The controlling pollutant in the genset compound, the plant maintenance shed during engine running tests, the hydrocarbon storage compound and any compound located within close range of active haul truck or excavator operations.
Carbon monoxide. 30 ppm TWA, 200 ppm peak. Genset combustion product, vehicle exhaust in the plant maintenance shed, fuel-handling area and any compound space adjacent to running diesel plant.
Nitrogen dioxide. 3 ppm TWA, 5 ppm STEL. Genset combustion product, vehicle exhaust, welding fume.
R32, R410A and R744 refrigerant. Manufacturer-published exposure limits for the inverter split systems, VRV and CO2 chiller serving the compound buildings. Leak detection on every plant room and corridor under AS/NZS 5149.
Formaldehyde. 1 ppm STEL. Applies to the construction laboratory if formaldehyde-based preservation is used in soil or concrete sample preparation.
Volatile organic compounds (general). Manufacturer-published exposure limits for the construction laboratory solvent storage, the welder portable shelter solvent line and the helipad refuelling enclosure.
Respirable dust. 10 mg/m³ TWA for inhalable nuisance dust. Applies to the construction laboratory concrete crushing rig, the aggregate sieve and any compound area adjacent to active construction.
Respirable crystalline silica. 0.05 mg/m³ TWA. Applies to the construction laboratory concrete crushing rig, the concrete cutting bench and any tunnel construction face where mechanised concrete cutting is performed.
Carbon dioxide. 5000 ppm TWA. The marker for overcrowded crib room and induction room ventilation, and the basis for demand-controlled ventilation across the compound.
Ozone. 0.1 ppm. Applies to any compound welding bay and any laser cleaning operation on rail or motorway construction.
Arsenic. Manufacturer-published exposure limits — rare on Australian construction, but occasionally relevant to specific welding fume profiles on older steel structures (heritage rail steelwork, older bridge refurbishment).

Layered on top of all of the above is the relevant state WorkSafe code for construction site sheds, lunch rooms and ablution blocks (Code of Practice for Construction Work in NSW, WorkSafe Victoria Construction Compliance Code, Workplace Health and Safety Queensland Construction Code, WorkSafe WA, ReturnToWorkSA and the Northern Territory and Tasmanian equivalents), and the project's Environmental Impact Statement (EIS) commitments where applicable. The HVAC ductwork specification does not directly engage with the EIS — but the boundary air quality monitoring at AS 3580 and the dust suppression strategy at the construction face does, and a tightened EIS condition can drive an additional dust extract zone inside the compound construction laboratory or at the plant maintenance shed.

Project typology — motorway versus rail versus tunnel versus wind versus solar versus hydro versus LNG versus mining

The Australian Tier 1 major infrastructure project comes in several distinct sub-types that affect the HVAC ductwork specification in non-trivial ways. The differences are scale, duration, climate, the construction work-face geometry and the operator's preferred subcontracting model.

Major motorway construction. WestConnex M4M5, M6 and M7 (CPB, John Holland and Samsung joint ventures), M6 Stage 1 (CPB and John Holland), North East Link (Spark joint venture with Acciona and Webuild), Western Harbour Tunnel and the various stages of the Bruce Highway upgrade in QLD and the Pacific Highway upgrade in NSW. The compound footprint sits on a rolling 1 to 5 km work face with multiple sub-compounds along the alignment, each housing 200 to 800 workers. The dominant HVAC challenge is the relocatable nature of the sub-compounds — the entire compound steps along the alignment every 6 to 12 months as the work face advances, which drives the duct geometry toward AS 4117 portable building integration and low-profile rectangular duct on the SBAL-V auto duct line. The senior PMO sits at a central compound that is more permanent for the project duration.

Major rail construction. Sydney Metro West (Lendlease, Acciona and Samsung joint venture), Sydney Metro Northwest legacy, Cross River Rail Brisbane (PULSE joint venture — CPB, UGL and John Holland), Suburban Rail Loop SRL VIC East and North (early works contracts), Inland Rail Sydney to Brisbane (multiple contracts along the 1,700 km alignment), Western Sydney International Airport rail (Bechtel, Lendlease and CPB). Rail construction compounds are similar to motorway compounds in their rolling work-face geometry, but with additional plant for sleeper placement, ballast handling, overhead line installation and signalling commissioning. The HVAC challenge includes the rail formation work zone where overhead line trains run during commissioning, and the rail signal commissioning room which needs clean redundant cooling for the signalling test gear. Major rail projects also drive Tier 1 contractors into joint ventures with specialist rail subcontractors — UGL and Downer for the rolling stock and overhead line, Siemens and Hitachi Rail and Alstom for the signalling.

Major tunnel construction. Melbourne Metro Tunnel (Cross Yarra Partnership joint venture — Lendlease, John Holland and Bouygues), Cross River Rail Brisbane, Sydney Metro West tunnels, WestConnex M4M5 tunnel, M6 Stage 1 tunnel, Western Harbour Tunnel, and the rail tunnels on Inland Rail through the Liverpool Plains and Toowoomba ranges. Tunnel construction adds the TBM headhouse with the launch shaft and the tunnel ventilation main fan plenum, the segment production and casting yard (refer to the precast concrete production article for the casting yard HVAC), the grout, foam and bentonite handling plant, the spoil conveyor and stockpile, the cross-passage and emergency egress construction sequence, and the confined space entry and rescue procedure under AS 1746. The TBM headhouse itself can be a Zone 1 or Zone 2 hazardous area under AS/NZS 60079 where methane potential exists along the alignment (particularly tunnels through coal measures or organic-rich sedimentary formations). The Melbourne Metro Tunnel and the WestConnex M4M5 both encountered methane along sections of the alignment. See our tunnel ventilation HVAC duct guide for the in-service tunnel ventilation specification.

Wind farm construction. Macarthur Wind in VIC, Goyder South Wind in SA, the Western Downs renewable energy cluster in QLD, the various Hunter Valley and New England Renewable Energy Zone (REZ) wind farms in NSW and the Pilbara renewable energy hubs in WA. Wind farm construction compounds are smaller than tunnel or motorway compounds — typically 150 to 600 workers at peak — but the duration is 12 to 24 months and the site footprint is large (50 to 200 km²). The HVAC challenge is the remote nature of most wind farm sites (typically 50 to 500 km from the nearest population centre), the dust load from the haul roads and the turbine erection sequence which drives the giant tower crane and 1,200-tonne mobile crane operator cab specifications. Each turbine tower is erected in 5 to 15 days and the compound steps along the site as the erection sequence advances.

Solar farm construction. Western Downs Solar in QLD, the Goyder Renewables Zone in SA, the Riverina Renewable Energy Zone in NSW and the various Pilbara solar projects in WA. Solar farm construction compounds are similar to wind farm compounds in scale and duration but with a higher density of workers per hectare during the panel installation phase. The HVAC challenge is the heat exposure — solar farm construction in the Pilbara and the QLD Western Downs runs through summer ambient temperatures of 40 to 48 degrees C, which drives the crib room cooling capacity and the medical centre heat stress provisions.

Hydroelectric and pumped hydro construction. Snowy 2.0 (Future Generation joint venture — Webuild, Clough and Lane Construction), Hume Dam upgrades, Marinus Link Tasmania-Victoria subsea cable landing, Cethana Pumped Hydro Tasmania and the various small-hydro upgrade projects across the East Coast. Snowy 2.0 is the dominant project — a 12-year construction window, 2,000 workers at peak, deep underground excavation through the Snowy Mountains for the 27 km headrace and tailrace tunnels and the power station cavern. The HVAC challenge inside the power station cavern construction is the underground ventilation main fan, the confined space rescue station every 500 m along the access tunnels, the rock-bolting machine fume capture, the shotcrete spraying dust extract and the deep underground crib rooms and amenity blocks. See our hydroelectric and pumped hydro HVAC duct guide for the in-service power station HVAC.

LNG construction. The major Australian LNG construction wave (Gorgon, Wheatstone, Ichthys, Prelude FLNG, Australia Pacific LNG, Gladstone LNG, Queensland Curtis LNG) is largely complete, but the residual brownfield expansion work at Pluto Train 2 and the future Browse and Scarborough projects keeps the LNG construction camp specification relevant. LNG construction camps are very similar to mining workforce camps in their accommodation, mess hall and recreation building specification — see our mining workforce camp HVAC duct guide for the dorm, mess hall and amenity specification. The LNG-specific elements are the LNG processing train assembly area (typically modular construction with marine module offloading at a dedicated berth), the cryogenic and process safety provisions and the AS/NZS 60079 hazardous area extent.

Mining construction. A new processing plant, a new rail line or a new port facility on a greenfield mining project. The construction camp itself is built to the mining workforce camp specification — see our mining workforce camp HVAC duct guide. The Tier 1 contractor compound supporting the construction is built to the project compound specification covered in this article.

Port construction. The various port expansion projects (Port of Newcastle, Port of Brisbane, Port Kembla, Port of Melbourne, Port of Fremantle, Port Hedland, Cape Lambert) involve marine module offloading, heavy lift cranes and a coastal compound exposure. The HVAC challenge is the coastal C5-M chloride exposure (within 10 km of the ocean) which drives 316L stainless on every external exhaust and the duct material premium on the compound. The container port HVAC duct article covers the in-service port HVAC.

The HVAC ductwork specification for the building-by-building walk-through that follows is written to the worst-case envelope — a multi-discipline tunnel-and-rail compound on a 24-month construction window, with full senior PMO, engineering office, subcontractor compound, crib room, first aid, construction laboratory, plant maintenance shed and hydrocarbon storage compound. Any departure from worst case (motorway-only compound without tunnel work, smaller solar farm compound without on-site laboratory, remote wind farm compound without 24/7 crib room) reduces the duct package scope but does not change the overall design logic.

Tier 1 contractor project HQ — Sydney, Melbourne, Brisbane, Perth and Adelaide

The Tier 1 contractor's project HQ in the major capital city is the corporate engine room for a major infrastructure project. It is not on the construction site — it is a leased or owned commercial fit-out in one of the major office towers — typically Barangaroo, Martin Place or the CBD core in Sydney; Collins Street, Bourke Street or Docklands in Melbourne; the Brisbane CBD or Fortitude Valley; the Perth CBD or West Perth; or the Adelaide CBD. The HVAC envelope is a commercial office tower fit-out, but the specific use case differs from a generic Class 5 office in several material ways.

The project HQ houses the senior project leadership — the project director, deputy project director, commercial director, engineering director, safety director, stakeholder director — and their direct teams. It runs the project board meetings, the joint-venture management committee meetings, the government client liaison meetings and the major project board steering committee. It contains a project war room with floor-to-ceiling project drawings, a secure document store for the contract package and a video conferencing suite that links to the on-site PMO, the client headquarters and the joint-venture partners worldwide. It typically operates 8 am to 8 pm five days a week with an extended 24/7 envelope during major project milestones (financial close, contract award, major milestone payment, dispute resolution, public hearings).

The HVAC specification for the project HQ:

AS 1668.2 outdoor air rate. 10 L/s per person at design occupancy for the open-plan office floor, 12 L/s per person for the project war room (higher occupancy density and longer continuous occupancy), 15 L/s per person for the boardroom and the major project board meeting room (highest density with continuous meeting use). ASHRAE Standard 62.1 cross-reference applied where the joint-venture partners include a multinational with global facility standards.
Acoustic target NC-35. Conversation privacy at the desk plus NC-30 in the boardroom and the major project board meeting room.
VAV terminal at every meeting room. Demand-controlled ventilation keyed to occupancy and CO2 at the breathing zone. The setpoint is typically 800 ppm at the boardroom (premium air quality target for senior executive meetings) and 1,000 to 1,200 ppm at the general office.
Dedicated CRAC redundant cooling on the IT, BIM and CAD floor. N+1 split system or VRF with crossover changeover on detection of unit failure. F7 filtration on the supply. UPS sized for 4 hours minimum on the IT cooling load. The BIM and CAD workstations each consume 800 to 1,500 W under model-rendering load, which drives the floor cooling demand above the per-square-metre commercial office benchmark.
Galvanised supply and return duct. 0.7 to 1.0 mm galvanised G300 Z275 to AS 4254.2. SBAL-V auto duct line on the rectangular runs (300 mm to 1,500 mm wide typical for a commercial floorplate riser and main run).
Stainless exhaust duct. 304 stainless on the amenity kitchen extract, the wet area exhaust, the executive bathroom extract. SBSF-1525 Stitchwelder on the welded sections and SBAL-V on the rectangular mechanical lock seam sections.
VRF or chilled water on the cooling distribution. Typical large Tier 1 project HQ exceeds 200 kW total cooling capacity, which moves the system architecture from a single packaged DX rooftop unit to a VRF system or a chilled water system with central chiller plant on the building roof.
R32, R410A or R744 (CO2) refrigerant. Depending on the building age and the joint-venture partner's refrigerant policy. AS/NZS 5149 leak detection on every plant room and corridor.

The duct stock for a typical 800 m² to 2,000 m² project HQ fit-out is in the band of 800 to 2,500 linear metres of rectangular galvanised supply and return duct, 200 to 600 linear metres of round galvanised branch duct for VAV terminal connections, 80 to 250 linear metres of stainless extract duct for amenity and wet area, and a balance of fittings, transitions and dampers. Total duct weight comes in at 8 to 25 tonnes depending on the size mix. Fabricated on a single SBKJ SBAL-V plus SBSF-1525 plus Gorelocker configuration, the duct package is a 4 to 8 week single-shift production run. See our commercial office tower HVAC duct guide for the commercial floorplate specification in full detail.

On-site project management office (PMO) — the engineering engine room on site

The on-site PMO is the second of the two project HQs — the on-the-ground equivalent of the corporate project HQ. It sits at a central compound on the major project site, typically a two-storey modular building or a stick-built portable office on relocatable foundations, with 400 to 1,500 square metres of office floorplate. The on-site PMO houses the on-site project director, the on-site engineering director, the construction managers, the site engineers, the planners and schedulers, the document controllers, the surveyors, the geotechnical engineers, the environmental managers, the safety managers and the community and stakeholder team. It runs the daily site coordination meetings, the weekly subcontractor meetings, the monthly progress reviews and the issue-by-issue technical reviews that drive the construction sequence.

The HVAC envelope is closer to a permanent Class 5 office than a transportable site shed because the PMO is the most permanent building on the compound and is typically conditioned to a higher standard than the surrounding subcontractor and crib rooms. AS 4117 portable building construction governs the structural envelope, AS 1668.2 governs the ventilation, AS 4254 governs the duct fabrication.

The HVAC specification for the on-site PMO:

AS 1668.2 outdoor air rate. 10 L/s per person at design occupancy for general office, 12 L/s per person for the PMO war room (where the daily site coordination meeting runs at peak occupancy of 30 to 60 people), 15 L/s per person for the major incident response room.
Module envelope. Typically 3.0 m wide by 12 m long for a single transport-module building, scaled up to 6.0 m wide by 12 m long for double-wide modules. Internal ceiling 2.7 m on a two-storey PMO module, ceiling void 300 to 500 mm for services. Low-profile rectangular duct fits the void at 100 to 200 mm depth.
Flexible flanged connections at module joints. Each module that ships to site separately has flexible flanged duct connections at the shipping interface, accommodating the relative module movement during transport and during seating on piers.
Cooling capacity. 60 to 150 W/m² depending on the workstation density and the IT load. Most on-site PMOs are conditioned by a VRF system with multiple outdoor units on the roof, sized for the design heat gain at the design summer ambient.
Acoustic target NC-35. Conversation privacy at the desk plus NC-30 in the project director's office.
Demand-controlled ventilation. CO2 sensors at the breathing zone driving the supply rate between 30 per cent at empty and 100 per cent at peak. Particularly relevant in the war room and the major incident response room where the occupancy spikes hard at meeting time.
Galvanised supply and return duct. 0.7 mm galvanised G300 Z275 to AS 4254.2. SBAL-V auto duct line. Low-profile rectangular duct fits the module ceiling void natively.
Stainless extract. 304 stainless on the amenity kitchen extract and the wet area exhaust in the PMO ablution block.

The PMO duct stock for a typical 800 m² double-storey building is in the band of 300 to 600 linear metres of rectangular galvanised duct, 80 to 200 linear metres of round galvanised branch and 30 to 80 linear metres of stainless extract. The duct ships flat-pack inside the modules from the AS 4117 portable building manufacturer's factory (Ausco Modular at Pinkenba, ATCO Structures and Logistics in Brisbane and Perth, BSI Group, McGrath Built Smart, Hutchinson Modular, EZE Group at the Civmec yard in Henderson WA, PD Building Group in NSW), fabricated by the builder's in-house duct shop or by a specialist subcontractor working to the builder's drawings on an SBKJ SBAL-V auto duct line. See our modular and prefab construction factory HVAC duct guide for the modular factory configuration.

Engineering, design, BIM and CAD office — clean redundant cooling at scale

The engineering, design, BIM and CAD office is a specialist sub-section of the on-site PMO or a co-located adjacent building. It houses the civil engineers, structural engineers, mechanical engineers, electrical engineers, geotechnical engineers, BIM coordinators, CAD drafters and clash-detection specialists. On a major rail or tunnel project, the office typically contains 40 to 120 engineers and drafters each running a high-spec workstation with 32-inch dual-monitor configuration, a centralised BIM server cluster, a large-format plotter line and a model coordination room with floor-to-ceiling display walls.

The HVAC challenge is the equipment heat load. Each engineering workstation consumes 600 to 1,200 W under continuous BIM rendering and clash detection. The BIM server cluster runs 5 to 15 kW continuous. The plotter line runs 1 to 3 kW intermittent with thermal peaks during printing. The display walls in the model coordination room run 8 to 20 kW continuous. The total IT and equipment load across a 60-engineer office sits at 60 to 120 kW continuous, on top of the 30 to 60 kW occupancy and ambient load. The cooling system has to handle this 24/7 in some cases — large multi-discipline coordination workshops often run overnight when the joint-venture partners' international offices are working in their own time zones.

The HVAC specification for the engineering and BIM office:

Clean redundant cooling. N+1 split system, VRF or precision CRAC on the workstation and server load. Crossover changeover on detection of unit failure. F7 filtration on the supply (some BIM rooms run to F9 where the project standard demands).
AS 1668.2 outdoor air rate. 10 L/s per person for the open-plan engineering floor, 15 L/s per person for the model coordination room with continuous high-density occupancy.
Acoustic target NC-35. Concentration is the priority — quiet supply duct, lined plenum at the fan discharge, low-velocity slot diffusers.
UPS on the cooling supply. The IT, BIM server and workstation cooling load runs through a UPS sized for 4 hours minimum, so a brief mains interruption doesn't crash a multi-hour model render.
Humidity control. 45 to 55 per cent RH year-round to protect the BIM server cluster and prevent static discharge at the workstation. Humidifier on the air handler or steam injection at the central plant.
Galvanised duct on supply and return. 0.7 to 1.0 mm to AS 4254.2. Lined supply duct where it enters the engineering and BIM rooms for acoustic comfort.

The engineering office duct stock is small per square metre (typically 0.4 to 0.7 m of duct per square metre of floor area) but the precision balancing and the redundant cooling architecture make the package higher value per linear metre than a generic office.

Site induction, training and orientation room

The site induction, training and orientation room is the first space every worker, visitor, subcontractor representative and government inspector enters on the major project. New workers complete a 2 to 4 hour induction package before being issued their site access pass, plus refresher training on a quarterly or six-monthly cycle. The room hosts 30 to 80 inductees per session, with 3 to 6 sessions per day during peak workforce mobilisation.

The HVAC specification:

AS 1668.2 outdoor air rate. 10 L/s per person at design occupancy. Class 9b assembly building under the NCC because the design occupancy exceeds 50 people in most major project induction rooms.
Acoustic target NC-35. Speech intelligibility is critical — the induction trainer speaks for 2 to 4 hours continuously and the inductees need to hear every word for the safety messages to land. Lined supply duct entering the room, lined plenum at the fan discharge, low-velocity slot diffusers at 1.5 to 2.0 m/s face velocity.
Demand-controlled ventilation. CO2 sensors driving the supply rate between 30 per cent during empty hours (between sessions) and 100 per cent during peak occupancy. The CO2 setpoint is 1,000 ppm at the speaker's breathing zone — staying below 1,200 ppm prevents the late-afternoon induction sessions from going stale.
Galvanised supply and return. 0.7 to 1.0 mm to AS 4254.2.
AV equipment cooling. The induction room contains a large-format display, projector or video wall, plus the speaker's lapel mic and the inductee response system. The AV equipment generates 2 to 6 kW of sensible heat that the cooling system has to handle on top of the occupancy load.

The induction room duct stock is conventional — typically 30 to 80 linear metres of rectangular galvanised supply and return for a 100 to 300 m² room, with the SBAL-V auto duct line handling the entire package in a single shift.

Subcontractor compound — multi-trade office, lunch room and amenity

The subcontractor compound is one of the largest single zones on a major project compound by footprint and by ductwork extent. A typical Tier 1 project with 2,000 workers and 50+ subcontractors has a subcontractor compound covering 5,000 to 15,000 m² of footprint, with dozens of individual donga offices, lunch rooms and storage sheds clustered around a central crib room, ablution block and induction interface. The subcontractors range from large multi-state firms (electrical contractors UGL, civil contractors CIMIC's CPB and BMD, mechanical contractors A.G. Coombs and Norman Disney & Young, communications contractors Service Stream and Ventia) to small specialist trade subcontractors (a single welder partnership, a specialist concrete cutting firm, an environmental monitoring subcontractor).

Each subcontractor has its own donga office for the supervisor, project engineer and document controller — typically 18 to 36 m² per donga, with 2 to 6 workstations and a small meeting table. Many subcontractors have a separate donga for their on-site fitters or labourers as a small lunch room. The central crib room is shared across the compound.

The HVAC specification for the subcontractor donga office:

AS 1668.2 outdoor air rate. 10 L/s per person at design occupancy.
Cooling capacity. 80 to 150 W/m² depending on the climate and the workstation density. Single 5 to 7 kW R32 inverter split system per donga, with the indoor unit ceiling-mounted or wall-mounted.
Acoustic target NC-35. Conversation privacy at the desk.
Module envelope. Typically 3.0 m wide by 6.0 m or 9.0 m long per donga, with internal ceiling 2.4 m and ceiling void 200 mm for services. Low-profile rectangular duct fits the void at 100 to 150 mm depth.
Galvanised supply and return duct. 0.5 to 0.7 mm to AS 4254.2 on the SBAL-V auto duct line.

A 50-donga subcontractor compound therefore needs 50 separate inverter split systems plus 50 small duct packages of 8 to 15 linear metres each, totalling 400 to 750 linear metres of duct across the compound. The duct is fabricated by the AS 4117 portable building manufacturer's in-house duct shop or by the duct subcontractor, on an SBKJ SBAL-V line in a single shift per 10 to 15 dongas.

Crib room and smoko — 24/7 staggered shift handling

The compound crib room or smoko room is the highest-loading single space on a major Australian construction project. A 2,000-worker project compound typically runs 4 shift changes per 24-hour day (day shift start, day shift end, night shift start, night shift end), with 200 to 500 workers transiting through the crib room at each shift change. The room is in heavy use for 4 to 8 hours out of every 24 and at low occupancy the remaining 16 to 20 hours. Peak occupancy density can reach 0.8 to 1.2 person/m² for short periods — denser than almost any other space across the project.

The HVAC specification:

AS 1668.2 outdoor air rate. 10 L/s per person at peak occupancy for a basic crib room with seating and microwave bank only. 15 L/s per person where the room is also used as a tea-room with a full kettle and toaster line, an espresso machine, a sandwich press and a hot food servery. The 15 L/s figure handles the elevated CO2 and water vapour generation from the heating appliances and the dense lunch traffic.
Demand-controlled ventilation. CO2 sensors at the worker breathing height driving the supply rate between 20 per cent at empty (between shift changes) and 100 per cent at peak. The CO2 setpoint is 1,000 to 1,200 ppm based on the AS 1668.2 indoor air quality target. Some Tier 1 contractors run a tighter 900 ppm setpoint where the crib room is the primary fatigue-management amenity.
Acoustic target NC-35. Conversation is the main acoustic load — lined supply duct entering the room, lined plenum at the fan discharge.
Refrigerator and microwave heat load. 6 to 12 refrigerators plus 6 to 12 microwaves and toasters generate 6 to 10 kW of sensible heat that the cooling system has to handle on top of the occupancy load.
Tea and coffee station local extract. Local extract over the kettle, toaster and espresso machine line at 100 to 200 L/s, ducted in 304 stainless to the building's general exhaust riser. The moist exhaust from the kettle bank is the highest-loading single duct stream in the crib room.
Sandwich press and hot food servery extract. Where the crib room contains a sandwich press, panini grill or hot food servery, dedicated local extract at 200 to 400 L/s in 304 stainless. Grease loading is light compared to a commercial kitchen, but the duct is still stainless on the exhaust side.
Heat recovery on extract. Sensible heat recovery on the bathroom and tea station extract to the fresh air supply, sized for 50 to 60 per cent recovery efficiency where the project sustainability strategy includes this.

The crib room duct is rectangular galvanised on the supply side and 304 stainless on the moist exhaust path over the tea station and the sandwich press. The duct stock for a typical 200 to 400 m² crib room serving 200 to 500 workers per shift change is in the band of 80 to 200 linear metres of duct including the local extract and the heat recovery interface.

First aid, medical centre and onsite doctor or nurse

The first aid and medical facility on a major Australian project ranges from a small first aid room staffed by a part-time medic to a full medical centre with an onsite doctor and nurse, an emergency response vehicle and a confined space rescue station. Large rail, tunnel and dam construction projects (Melbourne Metro Tunnel, Cross River Rail, Sydney Metro West, Snowy 2.0, North East Link) typically run a full medical centre because the medical evacuation distance to the nearest hospital is non-trivial and the response time matters for severe injuries.

The NCC classification depends on the staffing level. A small first aid room with first-aid-trained but not medically registered staff is Class 5 with health-care provisions. A full medical centre with a registered doctor or nurse is Class 9a (health-care building).

The HVAC specification for the full medical centre:

AS 1668.2 outdoor air rate. 10 to 12 L/s per person for the waiting room and consultation rooms, plus clinical dilution where infectious patients may be present. Treatment and trauma rooms typically run at 6 to 8 ACH with HEPA H13 filtration on supply.
Acoustic target NC-25. Speech privacy for consultations.
HEPA filtration. H13 on the supply to the consultation and treatment rooms, sized for the design supply volume.
Pressure relationships. Treatment room at slight positive pressure relative to the corridor (typically 5 to 10 Pa), trauma room at slight positive pressure relative to the treatment room, infectious isolation room (where present) at slight negative pressure relative to the corridor.
Medical refrigeration. Vaccine and medication fridge at 2 to 8 degrees C with continuous temperature monitoring and alarm at the medic's office. Refrigerant R134a or R600a depending on the unit. Battery UPS backup to maintain cold chain through a mains interruption — 4 to 8 hour minimum runtime.
Decontamination shower. Eyewash and emergency shower for chemical exposure response, with the drain to a holding tank for hazmat assessment before release to the project's wastewater system.
Confined space rescue station. Adjacent to the medical centre, with emergency air supply cylinder bank, rescue tripod, harness and stretcher store, and self-contained breathing apparatus (SCBA) bank for tunnel and shaft rescue under AS 1746.

The medical centre duct package is small but specialised. Typically 60 to 150 linear metres of rectangular galvanised supply and return with HEPA filter housings at the terminals, 30 to 60 linear metres of 304 stainless extract for the wet area and the decontamination shower, and dedicated extract over the trauma and infectious rooms. See our hospital and healthcare HVAC duct guide for the clinical pressure regime in full detail.

Construction laboratory — concrete, soil, aggregate testing with fume hood and dust extract

The construction laboratory on a major Australian project serves the on-site quality assurance function for concrete, soil, aggregate, asphalt, bitumen and structural steel testing. The laboratory typically handles 20 to 80 concrete cube tests per day, 5 to 20 soil density tests, 5 to 15 aggregate sieve tests and various ad-hoc material acceptance tests. On a major rail or tunnel project the laboratory is staffed by 4 to 12 technicians under a quality engineer, runs 12 to 16 hours per day across the day and afternoon shifts, and reports to the project quality director.

The NCC classification is Class 8 (laboratory) when fume hoods are installed for solvent or chemical testing, otherwise Class 5 (office) with laboratory ventilation provisions. The HVAC challenge is the dust load from the aggregate sieve and the concrete crushing rig, the cement and lime aerosol from the concrete mixer, the chemical fume from the bitumen and asphalt testing, and the heat load from the curing oven and the drying oven.

The HVAC specification:

AS 1668.2 general ventilation. 6 to 10 ACH across the laboratory floor at 8 hour TWA occupancy. Higher rates during active testing.
Fume hood face velocity. 0.5 m/s minimum at the sash face for any fume hood handling solvent, acid or organic vapour. AS 2243.8 governs the fume hood specification. The fume hood extract is in 304 stainless or PVC depending on the chemical profile, ducted to a roof-mounted exhaust fan with the discharge 3 m above the highest roof point within 15 m.
Aggregate sieve dust extract. Local extract over the rotary aggregate sieve at 5 m/s capture velocity, ducted in 304 stainless with a bag filter or cartridge filter before atmospheric discharge. The dust loading is high — 10 mg/m³ TWA is the AS 1668.2 nuisance dust limit but the actual concentration during sieve operation can exceed this without extract.
Concrete crushing rig dust extract. Local extract over the concrete cube crushing machine and any concrete cutting bench at 5 m/s capture velocity in 304 stainless with a bag filter before atmospheric discharge. Respirable crystalline silica at 0.05 mg/m³ TWA is the controlling pollutant — even small concentrations driven into the lab atmosphere require respiratory protection on the technician.
Bitumen and asphalt testing fume extract. Local extract over the bitumen heating bath and the asphalt mix design rig, in 304 stainless with appropriate gasket materials for the temperature range.
Curing oven and drying oven heat load. The curing oven runs at 60 degrees C continuous for concrete cube curing, and the drying oven runs at 105 to 110 degrees C for soil moisture testing. Total heat load 3 to 8 kW continuous. The cooling system has to handle this on top of the ambient load.
Pressure relationships. Laboratory at slight negative pressure relative to the corridor and adjacent office, so dust and fume don't migrate out of the lab. Typically 5 to 10 Pa negative.
Stainless duct on extract. All extract paths from fume hoods, aggregate sieve, concrete crushing rig and bitumen testing in 304 stainless on the SBSF-1525 Stitchwelder.
Galvanised supply. Conventional galvanised supply duct on the SBAL-V auto duct line, sized for the general ventilation rate and balanced against the extract for the design pressure relationship.

The construction laboratory duct package is the highest-specification single zone on the compound by duct material cost per linear metre. The stainless extract and the dust extract drive the price even though the total duct length is small (typically 80 to 200 linear metres across a 200 to 400 m² laboratory).

TBM (tunnel boring machine) headhouse — ATEX motors, confined space and methane purge

The tunnel boring machine headhouse is one of the most specialised HVAC environments on any major Australian infrastructure project. The headhouse sits over the launch shaft at the tunnel portal, houses the TBM main control room and the tunnel ventilation main fan plenum, and handles the supply and exhaust airflow for the TBM crew working at the cutterhead face 1 to 20 km from the launch shaft. The major Australian tunnel projects with active or recent TBM operations include the Melbourne Metro Tunnel (twin 9 km tunnels under the Melbourne CBD), Cross River Rail Brisbane (twin 5.9 km tunnels under the Brisbane River), Sydney Metro West (twin 24 km tunnels from Parramatta to the Sydney CBD), Sydney Metro Northwest legacy (15 km of tunnel), WestConnex M4M5 (twin 7.5 km tunnels under inner-west Sydney), M6 Stage 1 (twin 4 km tunnels), Western Harbour Tunnel (twin tunnels under Sydney Harbour) and the various rail tunnels on Inland Rail through the Liverpool Plains and Toowoomba.

The HVAC strategy at the headhouse:

Tunnel ventilation main fan plenum. A dedicated centrifugal fan rated for 100,000 to 500,000 L/s depending on the tunnel length and diameter. The fan supplies fresh air to the TBM crew at the cutterhead face through a large diameter duct (typically 1.4 to 2.0 m diameter) running along the tunnel crown back from the cutterhead. The plenum is 304 stainless on the welded longitudinal seams from the SBSF-1525 Stitchwelder for any zone that requires spark-resistant or chemical-resistant construction, otherwise galvanised G300 Z275 to AS 4254.2.
AS/NZS 60079 hazardous area classification. Where the tunnel alignment passes through ground with methane potential (coal measures, organic-rich sedimentary formations, peat) or where the TBM uses compressed-air intervention, the headhouse is classified Zone 1 or Zone 2 hazardous area. Ex d, Ex e or Ex p certified fan motors. Ex d certified light fittings. Ex i certified instrumentation. Earthing per AS 1768.
Methane purge fan. Where methane potential exists, a dedicated methane purge fan handles the displacement of any accumulated methane from the TBM cutterhead chamber and the man-lock during shift change. The fan is Ex d certified, ducted in 304 stainless or spark-resistant non-ferrous trim, with continuous methane monitoring at 25 per cent of LEL (lower explosive limit) as the trigger threshold for purge.
Confined space entry under AS 1746. The TBM cutterhead chamber and the man-lock are confined spaces under AS 1746. Entry requires continuous gas monitoring (methane, CO, CO2, O2), a rescue station with self-contained breathing apparatus (SCBA) and a permit-to-work cleared by the tunnel manager. The HVAC ductwork serving the man-lock entry interfaces with this entry procedure.
Grout, foam and bentonite handling extract. The TBM uses tail grout, foam and bentonite as part of the cutterhead operation. The handling area is a separate enclosure with dedicated local extract over the mixing tanks, in 304 stainless with appropriate gasket materials. Bentonite dust is a nuisance dust loading (10 mg/m³ TWA) that requires capture at source.
Spoil conveyor and stockpile extract. The tunnel spoil discharges onto a conveyor running back along the tunnel to the headhouse, then onto a surface stockpile or directly into trucks. The conveyor transfer points generate dust which is captured at source by local extract hoods, ducted in galvanised steel or 304 stainless to an outdoor cyclone or bag filter before atmospheric discharge.
TBM control room cooling. The TBM operator and the back-up cabin team work in a control room next to the headhouse, with workstation HVAC similar to the on-site PMO — clean redundant cooling, N+1 architecture, F7 filtration, 10 L/s per person fresh air, NC-35 acoustic.
Material selection. The headhouse duct mix is heavy on 304 stainless and spark-resistant non-ferrous trim because of the AS/NZS 60079 zoning. Galvanised is acceptable on the office and control room supply and return where the hazardous area classification does not reach.

The TBM segment production and casting yard, typically located adjacent to the headhouse or at a separate batching plant, is a precast concrete production environment. The HVAC specification for the casting yard is covered in the precast concrete production article — typically a long shed with overhead crane traffic, concrete batching at one end, segment formwork lines through the middle and segment curing chambers at the discharge end. Galvanised duct on the general ventilation and 304 stainless on the concrete cutting and aggregate handling extract.

See our tunnel ventilation HVAC duct guide for the in-service tunnel ventilation specification (jet fans, longitudinal ventilation, transverse ventilation, cross-passage pressurisation, smoke management) that the constructed tunnel hands over to the operator at commissioning. The headhouse described here is the construction-phase HVAC that supports the TBM operation, not the in-service tunnel ventilation.

Major motorway construction site office and rolling work face compound

The major motorway construction site office sits at the central compound on a multi-kilometre rolling work face. WestConnex M4M5 covered 7.5 km of inner-west Sydney with sub-compounds at each portal and at intermediate cut-and-cover sections. North East Link covers 6.5 km of north-east Melbourne with similar sub-compound geometry. M6 Stage 1 covers 4 km of southern Sydney with twin tunnels and surface roadworks. Western Harbour Tunnel covers Sydney Harbour with both immersed-tube and bored-tunnel sections.

The HVAC envelope at each motorway sub-compound is similar to the on-site PMO already described, but scaled smaller and with additional provisions:

Sub-compound office. Typically 300 to 800 m² of AS 4117 portable office building per sub-compound, housing the section manager, the engineers, the safety lead and the construction crew supervisors. Galvanised supply and return duct on the SBAL-V auto duct line. AS 1668.2 at 10 L/s per person.
Crib room. Local crib room at each sub-compound, sized for 50 to 150 workers per shift change. Same specification as the central crib room described above.
Amenity block. Local ablution block with WC and shower for the sub-compound workforce. 304 stainless extract at 25 L/s per WC and 25 L/s per shower under AS 1668.2.
Plant maintenance shed. Local plant maintenance shed for the section's earthmoving, paving and milling equipment. 6 to 8 ACH general ventilation, local welding fume capture, vehicle exhaust extract at the running bay. 304 stainless on the welding fume and vehicle exhaust paths.
Hydrocarbon storage. Section-level diesel storage typically 50,000 to 500,000 L for the section's plant fleet, classified per AS 1940 and AS/NZS 60079.
Traffic management compound. AS 1742 traffic signage storage and the on-site lane closure planning function. Conventional office HVAC with no special provisions.
Environmental monitoring compound. Dust, noise and water quality monitoring station with the environmental scientist team. Air sampling per AS 3580. Conventional office HVAC.

The duct package per motorway sub-compound is typically 600 to 1,800 linear metres of mixed galvanised supply and return plus stainless extract. Across a 7.5 km motorway with 6 sub-compounds plus a central PMO, the total compound duct package is 4,000 to 12,000 linear metres of duct. Fabrication is typically 12 to 20 weeks on an SBKJ SBAL-V plus SBSF-1525 plus Gorelocker configuration with a single shift.

Major rail construction project compound and rolling work face

The major rail construction project compound mirrors the motorway compound structure but with additional rail-specific elements. Sydney Metro West (the Lendlease, Acciona and Samsung joint venture covers the 24 km alignment from Parramatta to the Sydney CBD with multiple stations and TBM tunnels), Cross River Rail (the PULSE joint venture covers the 10.2 km alignment under the Brisbane River with new stations at Boggo Road, Woolloongabba, Albert Street and Roma Street), Suburban Rail Loop SRL VIC East (covering the south-east Melbourne arc), Inland Rail (covering the 1,700 km alignment between Brisbane and Melbourne with the major sections through the Liverpool Plains, Toowoomba and the Hunter Valley) and Western Sydney International Airport rail (the Bechtel, Lendlease and CPB joint venture covers the 23 km airport connection).

The rail-specific HVAC elements:

Rail formation work compound. Track-laying machine compound with sleeper handling, ballast handling and rail welding. Welding fume capture at 304 stainless duct, ozone monitoring at 0.1 ppm for the welding bay and any laser cleaning operation on rail steel.
Overhead line construction compound. 25 kV catenary line installation compound with cable handling, insulator assembly and pantograph testing rig. Conventional office HVAC with no special provisions, but with strict access control because of the high-voltage commissioning regime.
Signalling and communications compound. Train control system test compound with signalling test rig, train protection system test rig and communications equipment test rig. Clean redundant cooling on the test equipment — N+1 split system or VRF, F7 filtration, UPS on the cooling supply, 22 ± 1 degrees C and 45 to 55 per cent RH year-round for the signalling test gear.
Station construction compound. New rail station construction (Sydney Metro West stations, Cross River Rail stations, Suburban Rail Loop stations) typically has a dedicated construction compound at the station footprint, with the construction sequence overlapping the in-service rail operation. The station construction HVAC is conventional but the access constraint (working adjacent to live rail) drives a tighter safety regime. See our metro subway and rail station HVAC duct guide for the in-service station HVAC specification.
Tunnel construction compound. The rail-tunnel construction compound is similar to the motorway-tunnel TBM headhouse described above, with the additional consideration that the rail tunnel typically has cross-passages every 240 to 360 m for emergency egress, each requiring its own construction sequence and HVAC support.

Wind farm and solar farm construction site office and amenity

Wind farm and solar farm construction compounds are smaller and shorter-duration than tunnel or motorway compounds, but the remote locations and the construction sequence introduce specific HVAC challenges. Major Australian wind farm projects include Macarthur Wind in VIC (420 MW, 140 turbines), Goyder South Wind in SA (1,200 MW, 200 turbines, currently under construction), the Hunter Valley REZ wind clusters, the New England REZ wind clusters, the various Western Downs wind farms in QLD, and the Pilbara renewable energy hubs in WA. Major solar farm projects include Western Downs Solar in QLD (one of Australia's largest at 540 MW), the various Riverina REZ solar farms in NSW, the Goyder Renewables Zone solar farms in SA and the Pilbara solar projects in WA.

The HVAC specification for the wind and solar farm construction compound:

Site office. AS 4117 portable office building, 200 to 800 m², housing the project manager, the engineers, the safety lead and the document controller. AS 1668.2 at 10 L/s per person. Galvanised supply and return duct.
Crib room. 150 to 600 workers at peak across one or two shifts (wind and solar farms typically run a single day shift with overlap into early evening during summer to capture the daylight construction window). AS 1668.2 at 10 to 15 L/s per person.
Amenity block. Conventional 304 stainless extract.
Turbine erection crew compound. Where the wind farm uses giant tower cranes (climbing cranes that ride up the tower as the turbine is erected) plus 1,200-tonne mobile cranes, the erection crew has a dedicated small compound at each turbine pad. Typically a single 18 to 36 m² donga with split system HVAC.
Crane operator cab HVAC. Giant tower crane and 1,200-tonne mobile crane operator cabs are small cabinet split systems at 1.5 to 3.5 kW R32 capacity. AS 1668.2 at 5 L/s per person continuous fresh air. F7 filtration on supply to keep dust out of the cab. The crane operator works 8 to 12 hour shifts in the cab during turbine erection.
Substation and grid connection compound. The wind farm or solar farm substation compound is closer to an electrical infrastructure compound than a construction compound. AS 1668.2 at 10 L/s per person for the small control room, plus dedicated cooling for the transformer protection and SCADA gear. Conventional galvanised duct.
Solar panel installation crew amenity. Solar farm construction runs through summer in Western Downs (QLD) and the Pilbara (WA) at ambient temperatures of 40 to 48 degrees C. The crib room and the medical centre handle heat stress provisions — chilled water station, shaded outdoor seating with mechanical ventilation, dedicated cooling pod for heat stress response.

The wind and solar farm duct package per compound is typically 600 to 2,000 linear metres of duct, fabricated in 6 to 12 weeks on a single SBKJ SBAL-V plus SBSF-1525 configuration with a single shift.

Hydroelectric and pumped hydro construction — deep underground

Hydroelectric and pumped hydro construction is one of the most complex HVAC environments on any Australian major project. Snowy 2.0 (Future Generation joint venture — Webuild, Clough and Lane Construction) is the dominant project — 27 km of headrace and tailrace tunnels through the Snowy Mountains, a power station cavern 800 m underground, 2,000 workers at peak across a 12-year construction window. Marinus Link (TAS-VIC subsea cable, currently in development) and the Cethana Pumped Hydro project (Hydro Tasmania) are the other major pumped hydro projects in the pipeline.

The HVAC challenge inside the underground power station cavern construction sequence:

Underground ventilation main fan. A dedicated centrifugal fan handling the supply and exhaust airflow for the underground workforce. Plenum in 304 stainless or galvanised G300 Z275 depending on the chemical profile of the rock and any methane potential. AS/NZS 60079 zoning where the rock contains methane.
Confined space rescue station every 500 m. Along the access tunnels and the headrace tunnels, dedicated rescue stations with SCBA bank, rescue tripod, harness and stretcher store, and emergency communications. AS 1746 confined space monitoring at every station.
Rock-bolting machine fume capture. The rock-bolting machine uses resin grouting which generates VOC emissions during cure. Local extract at the bolting face in 304 stainless ducted to atmospheric discharge through a carbon filter or thermal oxidiser depending on the VOC profile.
Shotcrete spraying dust extract. The shotcrete (sprayed concrete) lining application generates cement aerosol and respirable crystalline silica. Local extract over the shotcrete robot at 5 m/s capture velocity in 304 stainless with a bag filter before atmospheric discharge.
Deep underground crib room and amenity. Where the construction workforce takes meal breaks underground (Snowy 2.0 has crib rooms 800 m below the surface in the power station cavern), the crib room HVAC follows the surface specification but with the air supply piped down from the surface through dedicated supply shafts. The fresh air supply to the crib room is part of the underground ventilation main fan plenum.
TBM operations. Snowy 2.0 uses three TBMs for the headrace and tailrace tunnels. The TBM HVAC follows the TBM headhouse specification described above but adapted to the underground geometry — the headhouse is the underground portal access shaft rather than a surface-level building.
Power station cavern HVAC. During the construction sequence, the cavern is conditioned by temporary HVAC for the construction crew working on the turbine and generator installation, the steel-lining welding and the cable-and-bus installation. Once the cavern is commissioned and the turbines come online, the permanent HVAC takes over.

See our hydroelectric and pumped hydro HVAC duct guide for the in-service power station HVAC specification that hands over to Snowy Hydro or Hydro Tasmania at construction completion.

LNG construction camp and mining construction camp

LNG construction camps and mining construction camps follow the same accommodation, mess hall, recreation and amenity specification as the workforce camps covered in our mining workforce camp HVAC duct guide. The Tier 1 contractor compound supporting the construction is built to the project compound specification covered in this article, but typically co-located with or adjacent to the construction camp. The Pluto Train 2 expansion at Karratha, the future Browse and Scarborough LNG projects, the various greenfield iron ore expansions in the Pilbara, the Bowen Basin coal expansions and the lithium and nickel construction camps across WA all follow this pattern.

The construction camp itself houses the construction workforce, while the contractor compound supports the project management, engineering and trade subcontractor functions. The two compounds are typically physically separated (the construction camp is closer to where the workers sleep, the contractor compound is closer to the construction face) but linked by a shuttle bus service and by a shared meal break schedule.

Construction plant maintenance shed — welding fume capture and vehicle exhaust extract

The construction plant maintenance shed handles the daily and weekly maintenance of the project's earthmoving and lifting equipment — excavators (Caterpillar, Komatsu, Volvo, Hitachi, Liebherr), bulldozers, graders, rollers, loaders, dump trucks (the largest typically 100 to 400 tonne haul trucks on a mining construction camp, 30 to 60 tonne articulated dumpers on a motorway construction project), mobile cranes (Liebherr, Manitowoc, Tadano, Grove), tower cranes (Liebherr, Potain, Wolffkran) and the various specialist construction plant (pile rigs, drill rigs, asphalt pavers, milling machines, soil stabilisation rigs).

The NCC classification is Class 8 (industrial workshop). The HVAC challenge is the welding fume from the on-site fabrication and repair work, the vehicle exhaust from the engine running tests, the hydraulic oil mist from the leak repair work and the heat load from the engines during diagnostic running.

The HVAC specification:

General ventilation. 6 to 8 ACH across the workshop floor at design occupancy. Conventional rectangular galvanised supply and return duct on the SBAL-V auto duct line.
Local welding fume capture. Capture velocity 0.5 m/s minimum at the source per AS 4836. Portable extract arm at each welding bay with HEPA filtration and discharge to atmosphere. 304 stainless on the extract duct because welding fume is corrosive and the duct interior collects fume particulate. SBSF-1525 Stitchwelder on the welded stainless extract sections.
Vehicle exhaust extract. Dedicated extract at the workshop running bay for engine diagnostic running tests. Flexible exhaust hose connection from the vehicle tailpipe to the rigid duct, with the rigid duct in 304 stainless ducted to atmospheric discharge through a high-velocity stack. Capture rate 100 to 200 per cent of the engine peak exhaust flow.
Diesel particulate matter monitoring. EC 0.1 mg/m³ TWA. Sensor at the workshop floor breathing zone to verify the extract is doing its job.
Carbon monoxide monitoring. 30 ppm TWA. Sensor at the workshop floor.
Ozone monitoring. 0.1 ppm. Sensor at the welding bay where TIG and MIG welding generates ozone.
Hydraulic oil mist extract. Local extract over the hydraulic test bench where leak repair work is performed, in 304 stainless with an oil mist coalescer filter before atmospheric discharge.
Heat load management. The diesel engine of a 50-tonne excavator running on the diagnostic bay generates 200 to 400 kW of thermal energy. The workshop HVAC has to either extract this directly through the vehicle exhaust extract (preferred) or handle it through general ventilation (acceptable for short runs).
Spark-resistant trim. Where the workshop performs routine plasma cutting or arc-air gouging, the surrounding ventilation duct is in spark-resistant non-ferrous trim or 304 stainless to prevent ignition of stray welding sparks against the duct interior.

The plant maintenance shed duct package is typically 200 to 800 linear metres for a 600 to 2,000 m² workshop, with a high stainless content (40 to 60 per cent of duct by weight) because of the welding fume, vehicle exhaust and oil mist extract paths.

Crane operator cab HVAC — small cabinet split system at scale

The crane operator cab HVAC is a very specific micro-HVAC environment. Tower cranes, climbing cranes, mobile cranes and crawler cranes on a major project have operator cabs at 30 to 100 m above ground level (for the tower and climbing cranes) or at ground level (for the mobile and crawler cranes). The cab volume is small — typically 1 to 2 m³ internal volume — and the operator works 8 to 12 hour shifts inside.

The HVAC specification:

Cabinet split system. 1.5 to 3.5 kW R32 capacity, with the indoor unit integrated into the cab structure and the outdoor unit mounted on the crane jib counterweight or boom. The indoor unit delivers 30 to 80 L/s of supply air.
AS 1668.2 outdoor air rate. 5 L/s per person continuous fresh air. The cab is small enough that the fresh air is supplied through a single inlet vent with the makeup-air balance through the cab door undercut.
F7 filtration on supply. Construction dust is the dominant air quality challenge for the crane operator. F7 filtration captures the inhalable dust fraction.
Acoustic target NC-35. The crane operator works in continuous concentration for a full shift — quiet HVAC matters.
Duct count minimal. Typically a single 100 mm flexible supply duct from the cabinet to the cab diffuser, plus the refrigerant pipework from the indoor to the outdoor unit. The flexible duct is fabricated to AS 4254.1.

A major project with 8 to 30 cranes therefore has 8 to 30 separate cabinet HVAC systems, each with a small flexible duct package. The total duct content is minor but the fabrication and installation logistics matter — each cab HVAC is commissioned at the crane assembly stage before the crane goes into service.

Welder portable shelter and confined space rescue station

The welder portable shelter is a temporary structure used for outdoor welding work on motorway barriers, rail signal gantries, wind turbine tower segments, hydroelectric pipe fittings and various structural steelwork. The shelter is typically a 3.0 m by 3.0 m or 4.0 m by 4.0 m fabric or steel-frame structure that the welder erects over the work piece to provide weather protection and to localise the welding fume capture.

The HVAC specification:

Local welding fume capture at the source. Portable extract arm with HEPA filtration, ducted in 304 stainless flexible duct, with the discharge routed to a portable scrubber or filter pack. Capture velocity 0.5 m/s at the welding arc per AS 4836.
AS 4836 welding fume control. The shelter incorporates the welding fume control hierarchy — substitution (low-fume electrodes where possible), local exhaust ventilation, general ventilation, respiratory protection.
AS/NZS 60079 spark-resistant. Where the shelter contains bottled gas storage (acetylene, oxygen, argon, CO2) the surrounding area is Zone 2 hazardous area. Spark-resistant or 304 stainless duct, Ex-rated electrical equipment.
Ozone monitoring. 0.1 ppm. TIG welding generates ozone — the shelter monitoring is part of the welder's PPE risk assessment.

The confined space rescue station supports tunnel, shaft, pit, tank and underground entry across the major project. It is co-located with the medical centre on the central compound, with secondary rescue stations distributed along the construction face (every 500 m in a tunnel, at every confined space access point on a wind farm tower or a hydroelectric pipe).

The HVAC and emergency air specification:

Emergency air supply. Compressed air cylinder bank with SCBA harnesses, sized for the design rescue scenario. Typically 60 to 120 minute breathing supply per cylinder, with multiple cylinders per station.
Rescue tripod and harness. Mechanical rescue gear for vertical extraction from a deep shaft or pit.
Stretcher store. Stokes basket stretcher and ancillary medical equipment for the casualty extraction.
Continuous gas monitoring. Methane, CO, CO2 and O2 sensors at the confined space access point, with alarm at the rescue station and at the compound control room.
AS 1746 confined space monitoring procedure. The rescue station is part of the permit-to-work system that controls confined space entry across the project.

Concrete placement and wet trades temporary shelter

Concrete placement and wet trades temporary shelter is a minor HVAC environment but worth listing because it crops up on every major project. The shelter is typically a fabric or steel-frame structure that the wet trades crew erects over a concrete pour or a tiling area to provide weather protection during the curing window. The HVAC is minimal — passive ventilation through openings in the shelter, with portable space heating in winter to keep the concrete cure temperature above the design minimum (typically 5 degrees C ambient).

The duct content is essentially nil — flexible ducting from a portable space heater to a directional discharge inside the shelter, fabricated to AS 4254.1 from a generic flexible duct supplier.

Construction dewatering pit and groundwater treatment

Major Australian rail tunnel and motorway tunnel construction (Melbourne Metro Tunnel, Cross River Rail, Sydney Metro West, WestConnex M4M5, M6 Stage 1, Western Harbour Tunnel, North East Link) all encounter significant groundwater inflow during the tunnel construction sequence. The dewatering pit is the surface-level installation that receives the pumped groundwater, treats it through a settlement and filtration train (typically primary settlement, polymer flocculation, sand filtration, pH adjustment and sometimes carbon polishing) and discharges to the stormwater system or to a local watercourse under an environmental approval.

The HVAC specification:

Confined space entry under AS 1746. The dewatering pit is a confined space — entry for cleaning and maintenance requires continuous gas monitoring (methane potential where the groundwater is in contact with organic-rich rock), a rescue station and a permit-to-work.
Mechanical ventilation of the pit. Continuous mechanical extract at 6 to 8 ACH while occupied, with a vapour-tight cover during unoccupied periods.
Chemical dosing area extract. Local extract over the polymer flocculant dosing tank and the pH adjustment tank in 304 stainless. The chemicals used are typically not hazardous in normal operation but the local extract handles the routine vapour generation.
Conventional Class 10b classification. Non-habitable building, no occupancy provisions beyond the maintenance access.

Hydrocarbon storage compound — bulk diesel, petrol, aviation fuel and LPG

The hydrocarbon storage compound is the highest hazard classification single zone on the project compound. A typical Tier 1 major project compound stores bulk diesel for the construction plant fleet (typically 50,000 to 1,000,000 L depending on the project scale and the remote-site logistics), petrol for utility vehicles (typically 20,000 to 50,000 L), aviation fuel for the project helipad where present (typically 10,000 to 30,000 L of jet fuel) and increasingly LPG for crib room kitchens and water heating (typically a 2,000 to 5,000 kg bulk tank).

The regulatory stack:

AS 1940. The storage and handling of flammable and combustible liquids. Sets the tank construction, the bund containment volume (110 per cent of the largest tank in any bund), the separation distance from buildings and boundaries, and the vapour management.
AS/NZS 60079. Explosive atmospheres. The hazardous area classification — the vapour space above the bulk tank is Zone 0, the area within 3 m of the tank shell and within 4.5 m of the fill point is Zone 1, the area within 4.5 m of any tank vent and within 7.5 m of the tank shell is Zone 2.
AS 4564. General requirements for gas supply (for any LPG bulk tank). Sets the tank construction, the regulator and the pressure relief.
AS 5601. Gas installations (for the LPG distribution from the bulk tank to the consumption point).
AS 3000. Electrical installations wiring rules. Ex-rated equipment within the hazardous area.

The HVAC specification:

Covered fuel transfer enclosure. Where the fuel transfer point is covered (typically for weather protection of the transfer pump and the operator), the enclosure has dedicated mechanical extract at the transfer face. 304 stainless or spark-resistant non-ferrous trim duct. Ex d or Ex e certified fan motor. Extract rate sized to maintain Zone 1 dilution below 25 per cent of LEL.
Vapour management on bulk tank. Piped vent on the bulk diesel and petrol tank, with the vent discharge at the design height above the highest local roof point. Not a duct system but a piped vent — the surrounding area ventilation is sized to dilute any fugitive emission.
LPG bulk tank. Above-ground horizontal LPG tank, with relief valve discharge at the design height. AS 4564 separation distance from buildings. AS/NZS 60079 hazardous area extends radially from the relief valve outlet.
Aviation fuel storage. Where the project has a helipad, the aviation fuel storage is typically a smaller above-ground or underground tank with high specification on the filtration and the quality assurance. The HVAC envelope is the same as the diesel storage — mechanical extract at the transfer point, Ex-rated equipment within the zone.
Battery storage. Increasingly, the project compound includes a battery energy storage system for solar PV firming. Battery rooms are classified per AS/NZS 60079 where the battery chemistry generates hydrogen (lead-acid, nickel-cadmium) — typically Zone 2 around the battery shelves. Lithium-ion batteries do not generate hydrogen in normal operation but have their own thermal runaway risk profile that drives a dedicated extract and the AS 3676 standby battery installation standard.

The hydrocarbon storage compound duct package is the highest specification per linear metre on the entire compound — 304 stainless or spark-resistant non-ferrous trim, Ex-rated terminations, welded longitudinal seams on the SBSF-1525 Stitchwelder. The duct length is small (typically 30 to 100 linear metres for the covered transfer enclosure and the relief valve venting) but the specification value is high.

Helipad and aviation refuelling enclosure

Many major Australian infrastructure projects include a project helipad for executive transfer (joint-venture senior management visits, government client visits, regulator visits), medivac response (severe-injury patient transfer to the nearest major hospital) and remote-site supply (specialist equipment delivery to remote tunnel portals, wind farm sites and hydroelectric construction). The Snowy 2.0 project, the Pluto Train 2 LNG construction, the Sydney Metro West, the Cross River Rail and the various Pilbara mining construction camps all have helipads.

The HVAC envelope:

Helipad apron. Outdoor open space, no HVAC. AS 1742 traffic signage on the approach.
Refuelling enclosure. Where the project provides on-site refuelling, the enclosure is typically a small open-sided shelter at the edge of the helipad with the fuel storage tank either inside the shelter or adjacent. AS/NZS 60079 Zone 1 within 1 m of the fuel transfer point and Zone 2 within 3 m. Dedicated mechanical exhaust at the transfer face in 304 stainless or spark-resistant non-ferrous trim. Ex d certified fan motor. Vertical discharge at 3 m above the highest roof point within 15 m.
Helipad lounge and waiting area. Where the project provides a covered helipad lounge for executive transfer and medivac waiting, the HVAC is conventional Class 9b assembly — 10 L/s per person, NC-35 acoustic, galvanised duct.

Project closeout commissioning office and asset handover

The project closeout commissioning office is the final building on the compound to demobilise. Once the major construction work is complete and the asset is handed over to the operator (Transport for NSW for the Sydney Metro West, Department of Transport Victoria for the North East Link, Cross River Rail Delivery Authority for the Cross River Rail, Snowy Hydro for Snowy 2.0, the wind or solar farm operator for the renewable energy projects, the LNG joint venture for the LNG projects), the commissioning office handles the final defect rectification, the punch-list closeout, the handover document compilation and the warranty period management.

The HVAC envelope is conventional Class 5 office, with the additional consideration that the office typically operates for 12 to 24 months beyond the bulk demobilisation of the construction workforce. The HVAC specification is therefore designed for a smaller occupancy than the peak PMO — typically 20 to 80 staff at this stage versus 200 to 600 staff at peak construction.

Subcontractor supply chain — A.G. Coombs, Norman Disney & Young, Ventia, UGL, Service Stream

The HVAC duct contractor supplying a major Australian Tier 1 project compound rarely deals directly with the Tier 1 contractor. The contract structure typically goes Tier 1 contractor — mechanical subcontractor — duct subcontractor. The mechanical subcontractors on the major Australian projects include A.G. Coombs Group (one of the largest mechanical services contractors), Norman Disney & Young (mechanical engineering consultancy), Ventia (formerly Broadspectrum, large-scale facilities and infrastructure services), UGL (CIMIC-owned, mechanical and electrical services), Service Stream (telecommunications and utility services with crossover into mechanical), and the various medium-sized mechanical contractors that specialise in modular construction (often working directly with Ausco, ATCO, BSI and McGrath modular builders).

The duct contractor's role in this contract chain:

Tender response. The duct contractor responds to the mechanical subcontractor's tender package with a quoted duct supply rate, lead time and quality dossier. The mechanical subcontractor compiles the duct quote into their overall mechanical tender to the Tier 1 contractor.
Design coordination. The duct contractor works with the mechanical subcontractor's project engineer on the duct layout, the fitting geometry, the access door positions, the support and hanger details, and the AS 4254 pressure class assignment.
Fabrication. The duct contractor fabricates the duct package at their shop using the SBKJ machine configuration (SBAL-V auto duct line, SBSF-1525 Stitchwelder, Gorelocker, Pittsburgh seam machine), delivers it to the site or the modular builder's factory in shipping-fit packages.
Installation support. The duct contractor's site team provides installation support to the mechanical subcontractor's installation crew, handles any field-cut modifications and signs off the as-built duct package.
Commissioning support. The duct contractor supports the mechanical subcontractor's commissioning engineer during the AS 1668.2 balance and the fire damper testing under AS 1851, with on-site coverage during the commissioning window.
Handover documentation. The duct contractor compiles the as-built duct drawings, the AS 4254 conformance certificates, the AS 1530.4 fire damper test certificates and the operator manual section covering the duct system, into the mechanical subcontractor's handover package.

The duct contractor's win in this contract chain is the SBKJ machine configuration. A contractor running an SBAL-V plus SBSF-1525 plus Gorelocker line can quote a 12 to 16 week lead time on a multi-tonne duct package versus the 20 to 30 week lead time of an outsourced quote, can absorb design changes during the construction sequence without breaking the schedule, and can deliver the duct in shipping-fit packages keyed to the modular builder's transport schedule.

Duct material selection — galvanised, 304, 316L and spark-resistant non-ferrous trim

The duct material specification across a Tier 1 major project compound follows a clear logic anchored to AS 4254 and the specific zone durability requirement:

Galvanised steel G300 Z275 to AS 4254. Project HQ supply and return, on-site PMO supply and return, engineering and BIM office supply and return, induction room supply and return, subcontractor compound donga supply and return, crib room supply, plant maintenance shed general supply and return, motorway and rail sub-compound office supply and return, wind and solar compound office supply and return. 55 to 65 per cent of the duct by weight on a typical compound.
Grade 304 stainless steel to AS 4254. Amenity kitchen extract (welded grease duct on the SBSF-1525), crib room tea station extract, ablution and wet area exhaust, construction laboratory fume hood plenum, construction laboratory aggregate sieve dust extract, construction laboratory concrete crushing dust extract, plant maintenance shed welding fume extract, plant maintenance shed vehicle exhaust extract, TBM headhouse fan plenum (where AS/NZS 60079 zone requires), helipad refuelling enclosure extract, hydrocarbon storage compound covered transfer enclosure extract, welder portable shelter local extract. 25 to 35 per cent of the duct by weight.
Grade 316L stainless steel. Coastal C5-M chloride exposure (Western Sydney Airport rail near Cumberland Plain, Newcastle Port, Brisbane Port, Perth Fremantle Port, Port Kembla, Marinus Link landing point, any Pilbara coastal mining construction camp). 3 to 8 per cent of the duct by weight where coastal exposure applies, otherwise zero.
Spark-resistant non-ferrous trim or 304 stainless. TBM headhouse where Zone 1 methane potential exists, hydrocarbon storage compound Zone 1 transfer enclosure, helipad refuelling Zone 1 transfer face, plant maintenance shed plasma cutting and arc-air gouging zone. Small percentage of duct by weight (typically 2 to 5 per cent) but very high specification value.

The SBAL-V auto duct line takes galvanised and 304 stainless coil interchangeably with a coil swap. The duct contractor runs a galvanised shift on the office, induction, subcontractor and crib room duct, swaps to stainless coil at the line, recalibrates the form rolls (which the SBKJ PLC handles automatically on coil entry), and runs the kitchen, ablution, laboratory and welding fume extract duct on the same line. The 316L stainless is run on the same line with a second coil swap. The spark-resistant non-ferrous trim is fabricated as a one-off batch on the SBSF-1525 Stitchwelder.

See our galvanised versus stainless steel duct guide for the material decision matrix and our welding methods guide for the stainless seam quality benchmark.

Module envelope and AS 4117 portable building integration

The vast majority of Tier 1 compound buildings are AS 4117 portable buildings — relocatable construction with modular geometry that supports the demobilisation at project completion. The AS 4117 builders supplying the Australian major-project sector include Ausco Modular at Pinkenba in QLD (the largest modular builder by volume), ATCO Structures and Logistics in Brisbane, Perth and Mount Isa (large modular builder with deep mining and major project portfolio), BSI Group (Building Solutions International, specialist modular builder), McGrath Built Smart Modular, Hutchinson Modular (a subsidiary of Hutchinson Builders), Easy Move Cabins (smaller-scale modular and shed supply), EZE Group at the Civmec yard in Henderson WA (mining construction modular) and PD Building Group in New South Wales (construction site sheds and modular offices).

The HVAC ductwork has to integrate with the AS 4117 module envelope:

Module width. Typically 3.0 m for road transport without an oversize permit, 6.0 m for double-wide modules with an oversize permit and a pilot vehicle. Most Tier 1 project compound modules are 3.0 m wide as the base building block, with double-wide modules used for the PMO and the central crib room where the larger floorplate matters.
Module length. Typically 6.0 m, 9.0 m, 12.0 m or 15.0 m, with 12.0 m as the most common single-module length.
Module height. 3.5 m maximum overall height for road transport without an oversize permit, which translates to a 2.4 to 2.7 m internal ceiling and a 200 to 400 mm ceiling void for services. The two-storey PMO uses two stacked modules with a structural connection between the floors.
Low-profile duct. Rectangular duct fits within the ceiling void at 100 to 200 mm depth — typical sizing 400 by 150 mm, 600 by 150 mm or 800 by 200 mm. SBKJ supplies low-profile rectangular duct down to 100 mm depth on the SBAL-V auto duct line for this application.
Flexible flanged connections at module joints. At every shipping interface where the duct crosses a module joint, a flexible flanged connection accommodates the relative movement between modules during transport and during seating on piers.
Union joints on rigid duct. Where a rigid duct crosses a module joint without flexible flanged connection, the duct is split at the module line with a union joint or a slip joint sealed with mastic on the upstream face.
Inverter split system per module. 2.5 to 5 kW R32 inverter split system per module for the smaller office and lunch room modules, with the indoor unit ceiling-mounted or wall-mounted and the outdoor unit on a rear-of-module bracket. Refrigerant pipework runs in the same ceiling void as the duct.
VRF or chilled water on the larger buildings. The PMO, the engineering office and the central crib room exceed the per-module split system capacity and move to a VRF or a chilled water system with central plant on the building roof.

See our modular and prefab construction factory HVAC duct guide for the modular factory duct shop configuration that supplies these compound buildings.

Cyclone, dust storm and wet season — duct in extreme conditions

Major Australian projects in the Pilbara, the Bowen Basin, the NT and the QLD coast operate in extreme weather conditions for parts of the year. The cyclone season runs from December to April across the northern coast (Region C and Region D wind classification under AS/NZS 1170.2), the wet season brings monsoonal rain and high humidity, and the dust storms (Pilbara and the NT) drive periodic dust events that load the HVAC supply filtration hard.

The duct specification adjustments for cyclonic and dust-prone regions:

Rooftop equipment tie-down. Every rooftop fan, plenum and roof penetration is tied down to AS/NZS 1170.2 wind loading certification. The duct connection to rooftop equipment is rigid flanged with bolted connection — no slip joint or self-locking joint that could shake loose in cyclonic wind.
Outdoor intake louvre. AS 4740 weather louvre with rain defeat for cyclonic horizontal rain. Low face velocity (1.5 to 2.0 m/s) to prevent water carry-over into the supply duct.
Outdoor air intake position. Above the predicted flood level for the compound's design flood event, and away from the prevailing wind direction during cyclone events.
Drainage on every horizontal duct run outside the conditioned envelope. Continuous fall to a low-point drain to clear any water that infiltrates during cyclonic horizontal rain.
Dust pre-filter at the intake louvre. 90 per cent efficient pre-filter at the louvre face to keep red iron ore dust (Pilbara, Roy Hill, Cape Lambert), coal dust (Bowen Basin, Hunter Valley) or arid-zone dust (Goldfields, Roxby Downs, Tanami) out of the supply duct.
Filter change schedule. Tightened from a generic 3 to 6 month change cycle to a 1 to 3 month change cycle during the dust storm season, with weekly differential pressure monitoring to flag accelerated loading.

SBKJ machine configuration for a Tier 1 major project duct contractor

For an Australian contractor or modular builder running an in-house duct shop to supply Tier 1 contractor compounds, major motorway, rail, tunnel, wind, solar, hydroelectric and LNG construction projects, the SBKJ baseline configuration:

SBKJ SBAL-V auto duct production line. The primary rectangular duct line. Galvanised G300 Z275 and 304 stainless coil capability. Forms rectangular duct from 200 mm to 1,500 mm wide on a single pass with TDF flange edges integrated. Coil thickness 0.5 to 1.2 mm galvanised, 0.5 to 1.0 mm stainless. Average single-shift output 800 to 1,200 linear metres of branch and trunk duct depending on the size mix. This is the workhorse for project HQ, on-site PMO, engineering office, induction, subcontractor compound, crib room, plant maintenance shed and amenity duct. See the SBAL-V product page for the full specification and the machine line-up for the configuration options. See also our SBAL-V versus SBAL-III comparison for the entry-level versus production-grade decision.
SBKJ SBSF-1525 Stitchwelder. The continuously welded stainless duct line for round and rectangular. Forms 304 and 316L stainless duct from 200 mm to 1,500 mm wide with continuously welded longitudinal seams. Coil thickness 0.5 to 1.5 mm. Used for commercial kitchen grease duct on the amenity, construction laboratory fume hood plenum, plant maintenance shed welding fume extract, vehicle exhaust extract, TBM headhouse fan plenum where AS/NZS 60079 zone applies, hydrocarbon storage compound covered transfer enclosure extract, helipad refuelling enclosure extract, welder portable shelter local extract.
SBKJ SB-ZF1500 Stitchwelder. The larger plenum stitchwelder for the heavy plenum sections — TBM headhouse main fan plenum, construction laboratory main extract header, larger hydrocarbon storage compound enclosure. Coil thickness up to 2.0 mm in 304 or 316L stainless.
SBKJ SBFB-1500 spiral former. The spiral round duct former for the multi-storey project HQ return riser, the dorm bathroom riser on any amenity block and the round branch duct that connects the rectangular trunk to the diffuser network. Galvanised and stainless coil capability.
SBKJ SBSF-1525 round-duct flanging. Round-duct flanging for the spiral riser interface to the rectangular trunk and for the fan plenum interface.
SBKJ SBPC1500 plasma cutting machine. The plasma cutting machine for the duct fittings, the access door cutouts, the spigot stub-outs and the irregular geometry that doesn't come off the auto duct line. Galvanised and stainless cutting capability.
SBKJ SBLR-600 longitudinal welder. The smaller longitudinal welder for the stainless cleanout doors, the access door collars and the dedicated welded fittings that the SBSF-1525 doesn't cover.
SBKJ Gorelocker. The mechanical lock seam machine for round and small rectangular duct. Used for bathroom riser branches, ablution extract branches, smaller branch duct on the subcontractor compound and the donga split system flexible duct connection collars.
SBKJ Bending Machine. The press brake for duct fittings, transitions and special-shape components. Forms the geometry that doesn't come off the auto duct line.

The capital cost of this expanded configuration is in the band of AUD 550K to AUD 1.1M depending on the exact line specification and the spare-parts and training package. The total cost of ownership over a 15-year horizon, accounting for the duct production it supports across multiple major project contracts, sits comfortably inside the cost of outsourced duct supply for any contractor of scale serving the Australian major project sector. See our HVAC duct production line TCO guide for the financial framework and our HVAC duct machine buyer's checklist for the procurement checklist.

Procurement and commissioning — the Tier 1 major project build sequence

A new Tier 1 major Australian infrastructure project typically follows a 12 to 60 month construction sequence depending on the project scale, from contract award to handover. Snowy 2.0 is a 12-year program at the high end. Major motorway tunnels are 5 to 7 years. Rail station upgrades are 3 to 5 years. Wind farm and solar farm construction is 18 to 30 months. The HVAC ductwork procurement and commissioning sits inside the sequence:

Months 0 to 3 — Tender and contract award. Tier 1 contractor wins the bid (CIMIC, John Holland, Lendlease, Multiplex, Hutchinson, BMD, Acciona, Ferrovial, Webuild, Downer, Civmec, Monadelphous, Worley, Macmahon, NRW, Decmil, BESIX). Joint-venture partner agreement signed. Project management office staffing decisions made.
Months 3 to 9 — Detailed design. The HVAC consultant (typically Norman Disney & Young, A.G. Coombs Design, Aurecon, AECOM, WSP, Arup or Stantec) produces the detailed mechanical design including the compound HVAC schedule. NCC classification matrix issued. AS 1668.2 ventilation rate calculation issued.
Months 9 to 12 — Mechanical subcontractor selected and duct contractor onboarded. Mechanical subcontractor (A.G. Coombs, UGL, Ventia, Service Stream) signs contract with the Tier 1 contractor. Duct subcontractor signs supply agreement with the mechanical subcontractor.
Months 12 to 18 — Duct machinery procurement. If the duct contractor is running an in-house duct shop, this is the window for SBKJ machine procurement. SBAL-V and SBSF-1525 lead time is 8 to 14 weeks from order to factory acceptance test. The duct contractor's working capital position determines whether the machine is bought outright or financed.
Months 18 to 30 — Compound construction and duct fabrication. Compound buildings constructed by the AS 4117 modular builder (Ausco, ATCO, BSI, McGrath, Hutchinson Modular, Easy Move, PD Building, EZE Group). Duct fabrication runs in parallel by the duct contractor on the SBKJ machine line. Duct ships flat-pack into the modules at the modular factory.
Months 30 to 36 — Compound mobilisation. Modules transported to site by road. Compound assembled on piers. Duct continuity restored at module joints. Central plant connected. Compound commissioned and the construction workforce mobilises.
Months 36 to 60+ — Construction execution. The bulk of the project construction window. The compound HVAC operates 24/7. Periodic maintenance, defect rectification, demand-controlled ventilation tuning.
Months X to X+24 — Demobilisation and asset handover. Compound demobilises in reverse order — the bulk subcontractor compound first, then the central PMO, finally the project closeout commissioning office. Modules trucked back to the modular builder's yard for storage or refurbishment. Duct contractor closes the as-built and warranty documentation.

The duct machinery procurement window at month 12 to 18 is the leverage point. A duct contractor who orders an SBKJ auto duct line at month 12 has the line commissioned by month 15 and can fabricate the compound duct in time for installation at month 22. A contractor who waits until month 18 to consider the duct production approach is forced into outsourced supply with a 6 to 10 week lead time on each batch, which is typically more expensive on landed cost and constrains the design flexibility on duct fittings.

Energy and decarbonisation — solar, demand control and heat recovery

The Australian construction sector is one of the largest single energy consumers across the economy, and the major project compounds are a non-trivial slice of the Tier 1 contractor's scope 1 and 2 emissions. The HVAC system across a 2,000-worker major project compound typically consumes 1,800 to 3,500 MWh per year of electrical energy across the project duration, depending on the climate and the operating profile. The decarbonisation playbook:

Rooftop solar at every compound building. A typical major project compound roof area is 8,000 to 20,000 m² of usable roof across the PMO, engineering office, subcontractor compound, induction room and amenity blocks, which translates to a 1.5 to 4.0 MW rooftop solar opportunity. The solar generation profile aligns well with the compound daytime HVAC load.
Battery energy storage. Pairing the rooftop solar with a 2 to 6 MWh battery energy storage system covers the evening peak load and reduces the grid draw, with a payback period of 4 to 7 years depending on the grid electricity price and the carbon price.
Demand-controlled ventilation everywhere. CO2 sensors in every occupied zone, VOC sensors in any chemical-handling zone (construction laboratory, welder shelter), humidity sensors in every wet zone (amenity, crib room tea station). The supply and exhaust airflow ramps in real time against the actual occupancy load rather than the design load.
Heat recovery on every exhaust. Sensible and latent heat recovery exchangers on the amenity bathroom extract, the crib room tea station extract, the construction laboratory general extract and the plant maintenance shed general extract. Typical recovery 60 to 75 per cent of available sensible heat.
Heat pump water heating. Replacing gas-fired or electric resistance water heating with heat pump water heating, with the heat pump evaporator drawing residual heat from the amenity extract or the plant maintenance shed extract.
Variable speed drive on every fan. Fixed-speed fan operation is the largest single waste of HVAC energy in a compound.
Electrified plant where possible. Heat pump rather than gas boiler on the air handler heating coil, removing the LPG input from the HVAC system. The genset bank still runs on diesel for the time being, but the compound HVAC moves to grid-electric or solar-electric.
ASHRAE Standard 90.1 energy performance reference. Major projects with a sustainability rating commitment (typically a Green Star or Infrastructure Sustainability Rating Tool target) reference ASHRAE 90.1 for the energy performance benchmark.

The duct design contributes to the decarbonisation outcome by minimising pressure drop and leakage. SBKJ duct manufactured to P1 supply class and P3 exhaust class meets AS 4254 leakage targets, and the integrated TDF flange on the SBAL-V line minimises field-applied sealant — which is typically the largest contributor to long-term duct leakage.

Common procurement mistakes in Tier 1 major project HVAC ductwork

The SBKJ engineering team has supported duct contractors and modular builders supplying Australian Tier 1 major projects for over a decade. The recurring procurement mistakes:

Treating the compound as a generic site shed project. A Tier 1 major project compound is not a single AS 4117 portable office — it is a small industrial estate with multi-class NCC classification. The project HQ is Class 5, the on-site PMO is Class 5, the induction is Class 9b, the crib room is Class 9b, the first aid is Class 9a, the construction laboratory is Class 8, the plant maintenance shed is Class 8, the hydrocarbon storage is Class 10b in a hazardous area. Each classification attracts a different ductwork specification.
Galvanised duct on the amenity wet area extract. The single most common premature duct failure on a compound. Galvanised lasts 4 to 7 years in continuous humid air with chlorinated water aerosols. Stainless lasts 20+ years. The material premium is recovered inside the first replacement cycle and the operator avoids replacing duct inside an occupied amenity block.
Under-specifying the amenity kitchen grease duct. AS 1668.2 commercial cooking clauses and NFPA 96 are non-negotiable for any compound mess hall or amenity kitchen. 1.2 mm stainless, continuously welded liquid-tight seams, 1 in 50 slope, cleanout at 3.5 m. Cutting corners here is a fire risk and a code violation.
Ignoring the hydrocarbon storage compound hazardous area classification. AS/NZS 60079 zoning of the hydrocarbon storage compound, the helipad refuelling enclosure and the TBM headhouse where methane potential exists is mandatory. Ex-rated equipment, spark-resistant or stainless duct, and a hazardous area dossier handed to the operator at commissioning.
Standard-profile duct in a low-profile module ceiling void. A 250 mm deep duct doesn't fit in a 200 mm ceiling void. AS 4117 module geometry drives low-profile rectangular duct down to 100 mm depth, which the SBAL-V handles natively but a generic duct line may not.
No flexible flanged connection at module joints. Modules move relative to each other during transport and during seating on piers. Rigid duct across a module joint cracks at the joint. Flexible flanged connections at every shipping interface.
Outsourced duct supply on a long-program project. The landed cost of outsourced duct supply on a 36-month project window is typically 25 to 40 per cent above in-house production by the modular builder or the duct contractor. The capital cost of the SBKJ machine line is paid back inside the first major project compound build.
No spare-parts continuity plan. The duct machinery is a 15-year asset. Without a 10-year parts continuity guarantee from the supplier, the duct shop is one PLC fault away from a six-month downtime. SBKJ commits in writing to 10-year parts continuity on every machine.
Ignoring the rolling work face geometry. A motorway or rail project compound steps along the alignment every 6 to 12 months. The duct package has to accommodate this — modular construction with shipping-fit packages keyed to the construction sequence, flexible flanged connections at every module joint, easy demobilisation and remobilisation at each step.
Under-specifying the construction laboratory fume hood plenum. The construction laboratory handles concrete, soil, aggregate, asphalt and bitumen testing — chemical fume, dust and heat load. The fume hood plenum has to be 304 stainless with welded seams, the dust extract has to handle respirable crystalline silica, and the general ventilation has to balance against the extract for the design negative pressure.
Missing the TBM headhouse AS/NZS 60079 zoning. Where the tunnel alignment passes through methane potential ground, the TBM headhouse is a hazardous area. Ignoring this is a regulatory failure and a safety risk.

Case study perspective — what a 2,000-worker tunnel project compound looks like in duct terms

To make the numbers concrete, here is a worked example of a hypothetical 2,000-worker Tier 1 tunnel project compound on a major Australian urban rail or motorway project. The numbers are illustrative rather than project-specific but they sit comfortably in the band of what our engineers see across the Australian sector.

The compound contains an on-site PMO of 1,200 m² across two storeys, an engineering and BIM office of 600 m², a 200-seat induction and training room with adjacent ablution, a subcontractor compound with 60 separate donga offices totalling 1,800 m², a central crib room of 400 m² serving 500 workers per shift change across four shift changes per day, a 200 m² first aid and medical centre with onsite doctor and nurse, a 250 m² construction laboratory with fume hood line and concrete crushing rig, a 1,500 m² plant maintenance shed handling 20+ pieces of major plant per day, a TBM headhouse over the launch shaft with the tunnel ventilation main fan plenum and the segment production yard adjacent, a 600 kL bulk diesel storage compound classified under AS 1940 and AS/NZS 60079, a 1,500 kg LPG bulk tank for the crib room kitchen, an aviation fuel storage tank for the project helipad, a 200 m² project closeout commissioning office (mobilised in the final 12 months), and the various confined space rescue stations, welder portable shelters and crane operator cabs across the construction face. Total roof area across the compound is approximately 8,500 m². Total installed cooling capacity is approximately 4,200 kW. Total installed supply air at design is approximately 70,000 L/s. Total installed exhaust air at design is approximately 30,000 L/s.

The duct stock to deliver that installation breaks down approximately as follows: 2,800 linear metres of rectangular galvanised supply duct between 200 mm and 1,200 mm, 1,400 linear metres of rectangular galvanised return duct between 400 mm and 1,500 mm, 1,200 linear metres of round galvanised branch duct between 100 mm and 250 mm for office, induction and crib room supply, 600 linear metres of rectangular 304 stainless extract duct for amenity, crib room tea station and ablution, 100 linear metres of welded 304 stainless grease duct for the amenity kitchen hood and rooftop fan run, 80 linear metres of welded 304 stainless makeup-air plenum for the amenity kitchen, 150 linear metres of welded 304 stainless construction laboratory fume hood plenum and dust extract, 250 linear metres of welded 304 stainless plant maintenance shed welding fume and vehicle exhaust extract, 60 linear metres of welded 304 stainless first aid and medical centre extract, 200 linear metres of welded 304 stainless TBM headhouse fan plenum and methane purge duct (where AS/NZS 60079 zone applies), 50 linear metres of spark-resistant non-ferrous trim or 304 stainless on the hydrocarbon storage compound covered transfer enclosure, 30 linear metres on the helipad refuelling enclosure, 80 linear metres on the welder portable shelters across the compound, and a balance of fittings, transitions and dampers. Total duct weight comes in at around 70 to 85 tonnes depending on the gauge mix.

Producing that duct stock on an SBKJ SBAL-V plus SBSF-1525 plus SB-ZF1500 plus SBFB-1500 plus SBPC1500 plus SBLR-600 plus Gorelocker configuration is a 16 to 22 week task with a single-shift dedicated crew. Outsourcing it on the open market is typically a 26 to 36 week supply chain with significant scheduling risk against the compound mobilisation date. The in-house production option is faster, lower landed cost, and gives the duct contractor full flexibility on fitting geometry, change orders and corrections during installation. The SBKJ line is paid back inside the first major project compound build, with subsequent compounds delivering pure margin against the depreciated machine base.

Operator and maintainer training — the people side

The HVAC ductwork inside a Tier 1 major project compound is a 5 to 15 year asset (the compound demobilises at project completion but the duct typically continues life on the next project or in long-term storage at the modular builder's yard) and the duct machinery that produces it is a 15-year asset. The people who operate both need training that sticks, and SBKJ structures the training in a way that aligns with how Australian duct contractors and modular builders actually staff their duct shops.

SBAL-V auto duct line operator training. 16 hours over two days on the production floor. Coil loading, line setup, PLC interaction, quality check at the discharge, common fault diagnosis and recovery. English language standard.
SBSF-1525 Stitchwelder operator training. 12 hours over two days. Welding parameter setup, stainless seam quality benchmark, kitchen grease duct specification, fume hood plenum specification, TBM headhouse plenum specification, NDT verification.
SB-ZF1500 Stitchwelder operator training. 8 hours on heavy plenum welding parameters and stainless seam quality on the larger gauge stock.
SBFB-1500 spiral former operator training. 6 hours on spiral seam quality and round duct geometry control.
SBPC1500 plasma operator training. 6 hours on plasma parameter setup, cut quality control and fume capture.
SBLR-600 longitudinal welder operator training. 6 hours on longitudinal seam quality on stainless cleanout doors and small fittings.
Maintenance training. 8 hours on the second day across the line. Preventive maintenance schedule, lubrication points, hydraulic system inspection, tooling regrind, sensor replacement, PLC software backup.
Commissioning report. Written report signed by the SBKJ commissioning engineer, listing every test run, every measured output and every adjustment. Becomes the baseline reference document for the duct shop's quality system.
Compound HVAC commissioning support. SBKJ engineers are available on a paid consulting basis to support the compound HVAC commissioning against AS 1668.2 design intent. This is in addition to the duct machinery commissioning and is typically engaged by builders who do not have a deep in-house HVAC engineering function.

How SBKJ supports Tier 1 major project duct fabrication

SBKJ's product line is purpose-built for HVAC duct contractors and the in-house duct shops of modular builders supplying the Australian Tier 1 major project sector. The capabilities relevant to a major project compound:

SBAL-V auto duct line. The workhorse rectangular duct line. Galvanised G300 Z275 and 304 stainless coil capability, 200 mm to 1,500 mm width, P1 to P3 pressure class, integrated TDF flange. Average single-shift output 800 to 1,200 linear metres. See the SBAL-V product page.
SBSF-1525 Stitchwelder. Continuously welded stainless duct for amenity kitchen grease, makeup-air plenum, laboratory fume hood, plant maintenance shed welding fume and vehicle exhaust, TBM headhouse fan plenum, hydrocarbon storage and helipad refuelling enclosure, and any other welded stainless duct on the compound.
SB-ZF1500 Stitchwelder. Heavy plenum stitchwelder for larger gauge stainless on TBM headhouse main fan plenum, large construction laboratory header and main hydrocarbon storage enclosures.
SBFB-1500 spiral former. Spiral round duct for multi-storey project HQ return riser, dorm bathroom riser and round branch duct.
SBPC1500 plasma cutting machine. Plasma cutting for fittings, access doors and irregular geometry.
SBLR-600 longitudinal welder. Longitudinal welded stainless cleanout doors and small welded fittings.
SBKJ Gorelocker and Pittsburgh seam machines. Round and rectangular branch duct for amenity, ablution and small subcontractor donga duct fabrication.
SBKJ Bending Machine. Press brake for duct fittings, transitions and special-shape components.
Australian engineering office in Box Hill North, Victoria. English-speaking after-sales, on-shore spare parts inventory for SBAL-V and SBSF lines, engineer-led commissioning support.
10-year parts continuity guarantee. In writing on every order.
Engineer-led 12-hour reply. All technical questions answered by an SBKJ mechanical engineer within 12 hours, not by a salesperson.
ARBS 2026 exhibitor. SBKJ and Australia Ducting Pty Ltd will be exhibiting at the Air Conditioning, Refrigeration and Building Services exhibition in Sydney in 2026 — the major sector trade event for Australian HVAC machinery and ductwork.

Talk to an SBKJ engineer about your Tier 1 major project duct package →

FAQ

Which NCC classifications apply across a Tier 1 major project compound?

A Tier 1 contractor compound on a major Australian motorway, rail, tunnel or wind farm project sits across multiple NCC Volume One classifications on the same site. The project HQ office and on-site PMO are Class 5 (office). The site induction and training rooms, subcontractor crib rooms and lunch rooms supplying more than 50 occupants, recreation rooms, conference rooms and visitor briefing rooms are Class 9b (assembly building). The first aid and medical facility is Class 9a (health-care building) when staffed by a doctor or nurse, otherwise Class 5 with health-care provisions. The construction laboratory for concrete, soil and aggregate testing is Class 8 (laboratory) when fume hoods are installed, otherwise Class 5. The plant maintenance workshop and welder portable shelter are Class 8. The genset compound, bulk diesel storage, LPG bulk tank and any helipad refuelling enclosure are Class 10b in hazardous area classification under AS/NZS 60079.

What ventilation rate does AS 1668.2 require for a Tier 1 project HQ office and on-site PMO?

AS 1668.2 requires 10 L/s of outdoor air per person for general office occupancy, which is the controlling rate for the Tier 1 contractor's project HQ in Sydney, Melbourne, Brisbane, Perth or Adelaide and for the on-site PMO. The same 10 L/s per person applies to the engineering, design and drafting office where the BIM, CAD and civil engineering teams work, although the higher equipment heat load drives the cooling capacity rather than the outdoor air rate. ASHRAE Standard 62.1 is the international reference standard that aligns to AS 1668.2 within engineering tolerance.

Does a TBM headhouse need ATEX-rated motors and spark-resistant duct?

Yes, when the tunnel alignment passes through ground with methane potential or when the TBM uses compressed-air intervention. AS/NZS 60079 applies to any enclosure where flammable atmosphere is reasonably foreseeable. On the Melbourne Metro Tunnel, Cross River Rail, WestConnex M4M5, Sydney Metro and similar major Australian tunnel projects, the TBM headhouse is typically Zone 2 around the launch shaft and Zone 1 at any compressed-air intervention chamber. HVAC ductwork serving the headhouse fan plenum is fabricated in 304 stainless or spark-resistant non-ferrous trim on the SBKJ SBSF-1525 Stitchwelder, with Ex d, Ex e or Ex p certified fan motors.

How do you ventilate a contractor crib room running 24/7 staggered shifts?

A subcontractor crib room on a major Australian infrastructure project typically serves 100 to 300 workers per shift change across three or four shift changes per 24-hour day. AS 1668.2 requires 10 L/s per person at sustained occupancy and 15 L/s per person where the room is also used as a tea-room. Demand-controlled ventilation with CO2 sensors at the breathing zone drives the supply rate between 20 per cent at empty and 100 per cent at peak, with the CO2 setpoint at 1,000 to 1,200 ppm. Local extract over the tea and coffee station at 100 to 200 L/s in 304 stainless duct handles the moist exhaust from the kettle and microwave bank.

What duct material applies to a major project hydrocarbon storage compound?

A major project hydrocarbon storage compound — typically bulk diesel for the construction plant fleet, sometimes petrol, sometimes aviation fuel for a project helipad and increasingly LPG for crib room and water heating — is a hazardous area under AS/NZS 60079 and AS 1940. The vapour space above the bulk tanks is Zone 0, the area within 3 m of the tank shell is Zone 1, and the area within 7.5 m is Zone 2. Any mechanical ventilation serving a covered fuel transfer enclosure is ducted in 304 stainless or spark-resistant non-ferrous trim, with Ex d or Ex e certified fan motors, and the duct discharge is at 3 m minimum above the highest roof point within 15 m.

Which SBKJ machine configuration suits a Tier 1 contractor or major project duct contractor?

The baseline SBKJ machine configuration is the SBAL-V auto duct production line for galvanised supply, return and general extract duct, the SBSF-1525 Stitchwelder for stainless commercial kitchen, construction laboratory, TBM headhouse, plant maintenance shed welding fume and hydrocarbon storage duct, the SBFB-1500 spiral former for multi-storey return riser, the SB-ZF1500 stitchwelder for heavy stainless plenum, the SBPC1500 plasma machine for cutting fittings and access panels, the SBLR-600 longitudinal welder for stainless cleanout doors and the SBKJ Gorelocker for round bathroom and amenity branches. The SBAL-V handles galvanised and 304 stainless interchangeably with a coil swap.

12-hour reply

Supplying duct into a Tier 1 contractor compound, on-site PMO, motorway tunnel TBM headhouse, rail construction project or major wind, solar or hydroelectric build? An SBKJ mechanical engineer in our Box Hill North Victoria office replies within 12 hours — not a salesperson.

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