Road Tunnel, Highway Tunnel Ventilation, Vent Stack and Underground Carpark HVAC Duct Guide — WestConnex, NorthConnex, West Gate Tunnel, CityLink, EastLink, Clem7, Transurban Operations, AS 1668.2 and NFPA 502

Why operating road tunnel ventilation is the highest-stake fire-life-safety scope in Australian civil infrastructure

Road tunnels in operation are the most demanding HVAC scope in the entire Australian civil infrastructure portfolio. The system has to dilute vehicle exhaust to below the AS 1668.2 engineering caps (25 parts per million carbon monoxide, 3 parts per million nitrogen dioxide) across every metre of a multi-kilometre tunnel at peak hour traffic loadings; clear smoke from a 30 to 100 megawatt design fire scenario within a few minutes against the buoyancy of hot smoke plume against the longitudinal traffic-direction velocity; discharge the exhaust air at sufficient elevation above the surrounding suburbs that the ground-level concentration of vehicle exhaust pollutants stays below the EPA ambient air quality standards; and operate continuously twenty-four hours a day for the next fifty to one hundred years across the asset operating life. There is no other building category in Australian civil engineering that combines those four constraints at the same scale.

The scale of the Australian road tunnel portfolio reinforces the responsibility. WestConnex in Sydney is Australia's largest infrastructure project by capital cost at AUD 21 billion — the Rozelle Interchange, M4-M5 Link, M4 Tunnel and M8 Tunnel forming a connected motorway tunnel network operated by Transurban (ASX:TCL) and opened progressively between 2018 and 2023. NorthConnex was Australia's longest tunnel in operation when it opened in 2020 — the 9 kilometre dual tube between the M1 and M2 at Wahroonga, operated by Transurban. The West Gate Tunnel in Melbourne, opened 2024, is Australia's largest single road tunnel infrastructure project at AUD 11 billion — Transurban-operated and constructed by the John Holland and CPB JV. CityLink (Burnley and Domain tunnels, opened 2000), EastLink (Mullum Mullum tunnel, ConnectEast operator, opened 2008), and the Brisbane tunnels (Clem7 opened 2010, AirportLinkM7 opened 2012, Legacy Way opened 2015 — all Transurban-operated) complete the eastern-seaboard portfolio. The Sydney Harbour Tunnel (RTA NSW, 1992 opening, toll road), M5 East Tunnel (RTA, 2001 opening, Sydney Airport access), Cross City Tunnel (2005 opening), Lane Cove Tunnel (2007 opening) and Eastern Distributor Tunnel (1999 opening) form the older Sydney CBD tunnel network. The South Road Stage tunnels in Adelaide (Torrens Junction and Glenelg-to-North-South Corridor, opening through to 2030) and the Sydney Gateway are the planned additions.

Every one of those tunnels has an HVAC duct package running into the tens of millions of dollars, an engineering scope that demands heavy-gauge spiral up to 2000 millimetre diameter, heavy-gauge rectangular up to 4000 millimetre width, 316L stainless welded vent stack interior lining and heavy-gauge fire-rated smoke spill duct certified to AS 1530.4 at 250 to 400 degrees Celsius for two to four hours. The HVAC ventilation engineer responsible for that package is dealing with a life-safety risk at the highest tier of the Australian civil engineering risk register — the consequence of a smoke spill failure during a tunnel fire is mass-casualty, the consequence of a vent stack emission failure is regulatory shutdown by the NSW EPA under the Protection of the Environment Operations Act or by the Victorian or Queensland EPAs under their state Environmental Protection Acts, and the consequence of a control centre HVAC failure is loss of the operator's ability to monitor and respond to traffic incidents on a major motorway network that carries hundreds of thousands of vehicles every day.

The four engineering questions that road tunnel HVAC has to answer at once are familiar to anyone who has worked underground carpark or metro rail ventilation, but the answers are different. The first is dilution of vehicle exhaust — CO at the AS 1668.2 25 parts per million engineering cap (tighter than the Safe Work Australia 30 parts per million STEL because the tunnel population includes commuters who lack the occupational training and PPE that an industrial worker carries), NO2 at the AS 1668.2 3 parts per million cap, diesel particulate matter at 0.1 milligrams per cubic metre elemental carbon and PM2.5 at 10 milligrams per cubic metre acute. The second is smoke spill in a tunnel fire scenario — the NFPA 502 design fire is a 30 megawatt heavy vehicle fire as the standard scenario, rising to 100 megawatts for a tanker fire scenario, with the smoke spill duct fire-rated to AS 1530.4 at 250 to 400 degrees Celsius for 2 to 4 hours depending on the fire engineering design. The third is vent stack emission control — the 80 to 100 metre stack at every modern tunnel portal discharges the bulk exhaust at sufficient elevation to keep the ground-level concentration of vehicle pollutants below the EPA ambient air quality standards, with optional chemical scrubber or activated carbon emission control on some installations under EPA condition. The fourth is the tunnel control centre HVAC — the Transurban Operations Centre and equivalent state road authority centres that monitor the tunnel network twenty-four hours a day require ASHRAE TC 9.9 Class A1 climate control with N+1 redundant cooling, communication-grade air filtration and emergency power backup that keeps the centre operational through any fault scenario.

Australian operating road tunnel portfolio — WestConnex, NorthConnex, West Gate, CityLink, EastLink, Clem7 and the rest

The Australian operating road tunnel portfolio is concentrated on the eastern seaboard — Sydney, Melbourne and Brisbane — with a smaller portfolio in Perth, Adelaide and the planned expansion under the South Road Stage. The largest single operator by network reach is Transurban (ASX:TCL), which holds the concession on the majority of the modern Australian toll road tunnel portfolio across the three eastern capital cities plus the Washington DC and Montreal international assets.

Sydney road tunnel network

Sydney holds the largest concentration of road tunnels in Australia. The historic network anchored on the Sydney Harbour Tunnel (1992 opening, RTA NSW, toll road) was progressively extended through the late 1990s and the 2000s with the Eastern Distributor (1999), M5 East (2001 opening, RTA, Sydney Airport access, 1.6 kilometre), Cross City Tunnel (2005 opening, toll road), Lane Cove Tunnel (2007 opening). The modern era of Sydney road tunnels begins with NorthConnex (2020 opening, Transurban, 9 kilometre M1-M2 link at Wahroonga, Australia's longest tunnel in operation at opening) and the WestConnex network which is itself the largest Australian infrastructure project ever delivered at AUD 21 billion capital cost. WestConnex comprises the Rozelle Interchange (opened 2023), the M4-M5 Link (opened 2023), the M4 Tunnel (opened 2019) and the M8 Tunnel (opened 2020), with Transurban operating the consolidated network through Linkt. The Sydney Gateway is the planned additional tunnel scope connecting Sydney Airport to the WestConnex network.

Every Sydney road tunnel has an operating ventilation HVAC package — jet fan longitudinal ventilation in the traffic tubes, vent stacks discharging exhaust at the portals (the Rozelle Interchange vent stacks at Rozelle, the NorthConnex vent stack at Wahroonga, the M5 East vent stack at Bexley, the M8 Tunnel vent stack at St Peters, the Cross City Tunnel vent stacks at Rushcutters Bay and Darling Harbour, the Lane Cove Tunnel vent stack at Lane Cove North, the Sydney Harbour Tunnel vent stack at North Sydney), smoke spill ductwork certified to AS 1530.4, emergency cross-passage pressurisation under AS 1668.3 zoned smoke control, and tunnel control centre HVAC at the M5 control centre and the WestConnex operations centre.

Melbourne road tunnel network

Melbourne's road tunnel portfolio is anchored on CityLink (Transurban, opened 2000, comprising the Burnley Tunnel eastbound and Domain Tunnel westbound under the Yarra River and the Melbourne CBD), EastLink (ConnectEast, opened 2008, comprising the Mullum Mullum Tunnel through the Mullum Mullum Creek catchment in Melbourne's east), and the West Gate Tunnel (Transurban, opened 2024, the AUD 11 billion West Gate Park to CityLink connector under the West Gate Freeway and the Yarra River). The West Gate Tunnel is Australia's largest single road tunnel infrastructure project by capital cost, constructed by the John Holland and CPB JV with vent stacks at Yarraville and Footscray and a sophisticated emissions monitoring program required as an EPA condition of operation. CityLink vent stacks are at the Burnley Power Station site, the Yarra River north bank and the Domain portal at the Royal Botanic Gardens.

The Melbourne road tunnel network extends to the CityLink Bolte Bridge approach tunnels at the South Wharf interface, and the planned North East Link (NEL) project which will add tunnel scope under the Yarra River between Greensborough and Bulleen — currently in construction by the Spark JV (Lendlease, John Holland, Webuild, Capella Capital). Mernda Rail Tunnel under the Metro Trains Melbourne network and the Melbourne Metro Tunnel under the CBD are the adjacent rail tunnel scope that interfaces with the road tunnel network at several crossover points.

Brisbane road tunnel network

Brisbane's road tunnel portfolio is anchored on the three Transurban tunnels — Clem Jones Tunnel (Clem7, opened 2010, the first major Brisbane motorway tunnel under the Brisbane River), AirportLinkM7 (opened 2012, connecting the Inner City Bypass to the Brisbane Airport), and Legacy Way (opened 2015, connecting the Western Freeway to the Inner City Bypass). All three tunnels share a common Transurban operations and monitoring approach, with vent stacks at Bowen Hills, Woolloongabba, Bowen Hills again and Toowong, and a coordinated emergency response across the three asset operations. Cross River Rail (opening 2026, dual rail tunnel under the Brisbane River and CBD, PULSE JV — CPB, UGL, John Holland) is the adjacent rail tunnel scope under construction by the Cross River Rail Delivery Authority on behalf of the Queensland Government and Brisbane City Council.

Perth, Adelaide, Hobart and Canberra

Perth has the Mitchell Freeway extension and the planned Perth to Adelaide highway corridor, with the road tunnel scope at the freeway connection points. Adelaide's road tunnel scope is dominated by the South Road Stage tunnels — Torrens Junction and the Glenelg-to-North-South Corridor — under the Department of Infrastructure and Transport SA, with opening expected through to 2030. Hobart's road infrastructure scope is currently the Bridgewater Bridge replacement (bridge, not tunnel). Canberra's road infrastructure includes the Belconnen Town Centre rail and road planning scope under the ACT Government and Roads ACT.

AS 1668.2 vehicle tunnel ventilation — fresh air supply, CO 25 ppm, NO2 3 ppm

AS 1668.2 (Mechanical Ventilation in Buildings) is the binding Australian Standard for road tunnel ventilation engineering, with the vehicle tunnel appendix providing the specific engineering caps and the fresh air supply calculation. The headline numbers are familiar to anyone who has designed an Australian basement carpark or road tunnel — fresh air supply at 1.0 to 1.5 cubic metres per second per traffic lane (the higher value applies to heavy traffic loadings and longer dwell times), carbon monoxide engineering cap at 25 parts per million (tighter than the Safe Work Australia 30 parts per million STEL because the tunnel population includes commuters), nitrogen dioxide engineering cap at 3 parts per million, and visibility (extinction coefficient) at 0.005 per metre as the design target for vehicle headlight effectiveness.

The engineering caps drive the demand-controlled ventilation logic. CO sensors at typically 100 to 250 metre spacing along the tunnel ceiling, NO2 sensors at the same spacing, visibility sensors and traffic detection sensors all feed the tunnel operations centre SCADA which modulates the jet fan speed and direction in real time. Under normal traffic flow the jet fans run at base load — typically 30 to 50 percent of maximum thrust — to maintain the longitudinal flow that pushes the exhaust toward the downstream vent stack. Under congestion or accident scenarios the jet fans ramp to higher speed to maintain CO below the 25 parts per million cap, with the operations centre alerting the road authority to consider traffic management intervention if the CO trend continues to rise. Under fire detection the jet fans switch to fire mode — direction-controlled to drive smoke toward the nearest vent stack while preventing back-layering against the direction of evacuation.

NFPA 502 Road Tunnels — the international engineering reference

NFPA 502 (Standard for Road Tunnels, Bridges and Other Limited Access Highways) is the international fire-life-safety engineering reference for road tunnels worldwide. The standard is published by the National Fire Protection Association and is referenced by every modern road tunnel ventilation engineer alongside the local jurisdiction's national or state standards. In the Australian context, AS 1668.2 is the binding standard but NFPA 502 is the practical engineering reference for jet fan thrust calculation, smoke spill direction logic, evacuation pathway pressurisation and tunnel fire scenario response.

NFPA 502 defines the design fire scenarios. The standard design fire is 5 megawatts for a passenger car, 30 megawatts for a heavy vehicle (truck), 100 megawatts for a tanker (petroleum or liquefied gas). The road tunnel ventilation engineer designs the smoke spill system against the design fire — typically the 30 megawatt heavy vehicle scenario as the engineering design point, with the 100 megawatt tanker scenario as the upper bound for sensitivity analysis. The smoke spill flow rate required to maintain critical velocity (the longitudinal flow velocity that prevents back-layering of smoke against the downstream direction) is calculated against the design fire — for a typical 4-lane Australian tunnel with a 30 megawatt design fire, the critical velocity is approximately 2.7 to 3.0 metres per second and the smoke spill flow rate is approximately 200 to 400 cubic metres per second. The smoke spill duct fire rating to AS 1530.4 at 250 to 400 degrees Celsius for 2 to 4 hours is the construction-side response to the smoke spill flow rate calculation.

NFPA 502 also defines the ventilation system types — longitudinal (jet fans drive air along the tunnel in one direction, the standard modern Australian approach), transverse (supply and extract running along the tunnel at intervals, the legacy approach used in older tunnels), semi-transverse (supply or extract only, intermediate approach), and extract (extract-only at portals, used in shorter tunnels). The Australian road tunnel portfolio is almost entirely longitudinal jet fan in the modern tunnels (West Gate, WestConnex, NorthConnex, Clem7, AirportLinkM7, Legacy Way) with some transverse legacy installations in the older Sydney tunnels.

Jet fan longitudinal ventilation — 300 to 700 Newton thrust, 600 to 1200 mm axial fan

Jet fans are the workhorse of modern Australian road tunnel ventilation. Each fan is an axial flow fan with aluminium hub blades and a stainless steel or fire-rated steel casing, typically 600 to 1200 millimetre diameter, fire-rated to AS 1530.4 at 250 to 400 degrees Celsius for 2 to 4 hour duration. The fan motor is a 30 to 75 kilowatt squirrel cage induction motor with variable speed drive and bidirectional capability — the fan can drive air in either direction through reversing the motor and pitching the blades. Each fan delivers 300 to 700 Newtons of thrust at the discharge nozzle, with the thrust matched to the design longitudinal velocity and the fan spacing along the tunnel ceiling.

Jet fan suppliers to Australian road tunnels

The Australian road tunnel jet fan supplier list includes the global tunnel ventilation specialists and several regional suppliers:

• Colt International — global ventilation specialist with tunnel jet fan portfolio.
• Greenheck — US-headquartered ventilation specialist with tunnel jet fan product line.
• Twin City Fan — US-headquartered industrial fan specialist.
• Aerovent — industrial fan specialist with tunnel ventilation portfolio.
• Systemair — Swedish-headquartered ventilation specialist with global tunnel fan portfolio.
• S&P Soler & Palau — Spanish-headquartered ventilation specialist with tunnel jet fan product line and Australian distribution.
• Howden — global industrial fan specialist with tunnel ventilation portfolio and Australian operations.
• Industrial Wind — industrial fan specialist with tunnel ventilation portfolio.
• Sahbox Ventilation — tunnel ventilation specialist.
• Pacific Ventilation — Australian regional ventilation specialist.
• Aerofoil — Australian and global axial fan specialist.
• Australian Made TVS — Australian tunnel ventilation specialist.
• EBM-Papst — German-headquartered ventilation specialist with global tunnel jet fan portfolio.

Jet fan spacing and thrust calculation

Jet fan spacing along the tunnel ceiling is typically 80 to 150 metres, with the spacing matched to the fan thrust and the design longitudinal velocity calculation. The critical velocity for a 4-lane tunnel with a 30 megawatt design fire is approximately 2.7 to 3.0 metres per second, and the total thrust required to maintain that velocity against fire-induced pressure drop is in the 50 to 200 kilonewton range across the full tunnel length. The total thrust is divided into the number of fans operating in parallel — a typical 3 kilometre tunnel with 1000 metre fan-spacing at 700 Newton per fan and 4 fans in parallel across the tunnel cross-section delivers 28 to 112 kilonewton total depending on the redundancy strategy and the design margin.

Jet fan plenum and connection duct

The jet fan plenum is the rigid duct section that mounts the fan to the tunnel ceiling and routes the inlet and outlet airflow. The plenum is typically heavy gauge galvanised or stainless steel 1.6 to 3.0 millimetre, fabricated on the SBKJ SBAL-V auto duct line in galvanised G275 or 316L stainless configuration, with the welded longitudinal seam on the SBKJ SB-ZF1500 longitudinal stitchwelder. The plenum is fire-rated to AS 1530.4 at the same 250 to 400 degrees Celsius 2 to 4 hour duration as the fan itself, ensuring the entire jet fan assembly survives the design fire scenario.

Vent stack 80 to 100 metres — chemical scrubber, activated carbon, EPA stack emission monitoring

The vent stack at every modern Australian road tunnel portal is the visible piece of the operating tunnel HVAC scope. The 80 to 100 metre stack discharges the bulk tunnel exhaust at sufficient elevation above the surrounding residential and commercial properties that the ground-level concentration of vehicle exhaust pollutants stays below the EPA ambient air quality standards. The stack height calculation is set by the dispersion modelling — typically using the AUSPLUME, CALPUFF or AERMOD model with the local meteorological data — to demonstrate compliance against the NSW EPA Approved Methods for the Modelling and Assessment of Air Pollutants, the Victorian EPA air emission protocol, or the Queensland DES air emission guideline.

Major Australian vent stack examples

The most visible Australian vent stacks include:

• Rozelle Interchange WestConnex vent stacks — at the Iron Cove portal and the City West Link interface, Transurban operated, opened 2023.
• NorthConnex Wahroonga vent stack — at the M1 northern portal, Transurban operated, opened 2020.
• West Gate Tunnel vent stacks — at Yarraville and Footscray, Transurban operated, opened 2024.
• CityLink Burnley and Domain vent stacks — at the Burnley Power Station site and the Domain portal at the Royal Botanic Gardens, Transurban operated, opened 2000.
• EastLink Mullum Mullum vent stacks — at the Mullum Mullum portals, ConnectEast operated, opened 2008.
• Clem7 vent stacks — at Bowen Hills and Woolloongabba, Transurban operated, opened 2010.
• AirportLinkM7 vent stacks — at Bowen Hills, Transurban operated, opened 2012.
• Legacy Way vent stack — at Toowong, Transurban operated, opened 2015.
• M5 East vent stack — at Bexley, RTA NSW, opened 2001.
• Cross City Tunnel vent stacks — at Rushcutters Bay and Darling Harbour, opened 2005.
• Lane Cove Tunnel vent stack — at Lane Cove North, opened 2007.
• Sydney Harbour Tunnel vent stack — at North Sydney, RTA, opened 1992.

Vent stack structural design — AS/NZS 1170.2 wind, AS/NZS 1170.4 earthquake

The vent stack structural design follows AS/NZS 1170.2 (Structural Design Actions Part 2: Wind Actions), AS/NZS 1170.4 (Earthquake Actions in Australia) and AS 1170.5 across the typical 80 to 100 metre height. The structure is typically reinforced concrete with stainless or aluminium cladding, with the interior lined with 316L stainless welded ductwork to handle the corrosive exhaust gas chemistry. The wind loading calculation includes the dynamic response of the slender structure to gusting wind, with the design wind speed varying by region under the AS/NZS 1170.2 region map. Sydney and Brisbane are Region A (non-cyclonic), Melbourne is Region A, Perth and Adelaide are Region A, and the northern tropical zone (Darwin, North Queensland) is Region C or D (cyclonic). The earthquake loading is generally low across most of Australia (compared to seismically active regions) but the slender 80 to 100 metre stack still requires the AS 1170.4 dynamic analysis.

Vent stack interior duct lining — 316L stainless welded

The vent stack interior duct lining is 316L stainless welded construction throughout the discharge path because the exhaust gas chemistry includes nitric acid from NO2 dissolution in condensed moisture and sulphuric acid from SO2 dissolution (rare in modern vehicle exhaust but historically significant), which would attack galvanised or carbon steel duct within a few years and reduce the asset operating life to well below the 50 to 100 year target. The 316L stainless lining is fabricated on the SBKJ SBAL-V auto duct line in 316L stainless configuration, with the welded longitudinal seam on the SB-ZF1500 longitudinal stitchwelder. Heavy gauge plate sections (above 3 millimetre) are cut on the SBPC1500 plasma cutter. Field installation welding is on the SBLR-600 inverter welder with ER316L stainless filler wire per AS/NZS 1554.6 stainless welding qualification.

Vent stack fan room — 4 to 12 axial fans in parallel

The vent stack fan room at the base of the stack houses the extract fans — typically 4 to 12 axial fans in parallel, each 1.5 to 3 metres diameter, delivering 50 to 200 cubic metres per second per fan and a total stack extract flow of 200 to 1500 cubic metres per second depending on the tunnel size. The fans are fire-rated to AS 1530.4 at 250 to 400 degrees Celsius 2 to 4 hour duration, ensuring continued operation during the design fire scenario. The fan motor is typically a 75 to 250 kilowatt squirrel cage induction motor with variable speed drive. The fan supplier list overlaps with the jet fan supplier list — Colt, Greenheck, Twin City, Aerovent, Systemair, S&P, Howden, EBM-Papst.

Chemical scrubber and activated carbon emission control

Some Australian tunnel vent stacks include chemical scrubber or activated carbon emission control as an EPA condition of operation. The chemical scrubber removes NO2 and SO2 from the exhaust gas through wet contact with a chemical reagent (sodium hydroxide for NO2 and SO2, or specialised proprietary reagents). The activated carbon plenum removes hydrocarbons, benzene and other volatile organic compounds through adsorption on activated carbon media. Both systems require periodic regeneration or replacement of the scrubber chemistry or carbon media. The scrubber plenum and the activated carbon plenum are constructed in 316L stainless welded construction because of the corrosive chemistry inside the plenum.

EPA stack emission monitoring

EPA stack emission monitoring is mandatory in NSW (under the Protection of the Environment Operations Act POEO administered by the NSW EPA), VIC (under the Environment Protection Act administered by the Victorian EPA) and QLD (under the Environmental Protection Act administered by the Queensland Department of Environment and Science DES). The monitoring system includes continuous CO, NOx, particulate matter (typically PM10 and PM2.5), opacity, stack gas temperature, stack gas velocity and stack flow rate measurement at the stack exit. The data is logged at the tunnel operations centre and reported to the EPA on a quarterly or annual basis depending on the licence condition. Stack emission limit exceedance triggers an EPA notification and a corrective action investigation. The community complaint mitigation strategy that emerged post-2018 after the WestConnex and NorthConnex community engagement on tunnel emissions is the strategic context for the modern Australian vent stack design.

Smoke spill duct fire-rated to 250 to 400 degrees Celsius 2 to 4 hour AS 1530.4

Smoke spill ductwork is the highest-stake construction-side scope in the entire road tunnel HVAC package. The duct handles the tunnel exhaust during a fire scenario — pulling smoke out of the burning section of the tunnel and routing it to the nearest vent stack while the jet fans drive the longitudinal velocity in the design direction. The duct fire rating is set by the design fire scenario and the smoke temperature profile — 250 degrees Celsius for 2 hours is typical for underground carpark and shorter tunnel scope (4 to 8 megawatt design fires), 400 degrees Celsius for 4 hours is typical for major road tunnel scope (30 megawatt heavy vehicle and 100 megawatt tanker design fires).

Smoke spill duct construction

The smoke spill duct construction is heavy gauge galvanised or carbon steel 2.0 to 4.0 millimetre, with welded longitudinal seam on the SBKJ SB-ZF1500 longitudinal stitchwelder, transverse joint with intumescent gasket, and fire dampers per AS 1530.4 at every fire compartment boundary. The duct lining and external insulation is calcium silicate, mineral wool or fire-rated board sized to achieve the AS 1530.4 furnace test pass at the design temperature and duration. The SBKJ SBSF-1525 slitter prepares the plate stock from coil at the design width, and the SBPC1500 plasma cutter cuts the plate for transitions and access panels.

Fire fan control panel FFC

The fire fan control (FFC) panel is the system that monitors the fire detection signals from the tunnel ceiling-mounted detectors (linear heat detection cable, optical smoke detection, vehicle thermal imaging) and commands the response sequence — activating the smoke spill fan, opening the relevant smoke spill damper at the fire-affected zone, closing the supply damper at the adjacent zones, and reversing or pitching the jet fans to the fire-mode direction. The FFC panel response time is typically within 30 seconds of the first fire detector activation, with the smoke spill flow at design within 60 to 120 seconds depending on the fan startup ramp. The FFC panel is monitored at the tunnel operations centre via SCADA, with the operations centre operator able to override or assist the automatic response logic.

AS 1851 routine service — smoke spill activation drill

AS 1851 (Routine Service of Fire Protection Systems and Equipment) sets the periodic functional test schedule for the smoke spill system. The annual functional test of the entire smoke spill system includes jet fan thrust test (verify each fan delivers the design thrust within tolerance via Pitot tube discharge velocity measurement and motor electrical input correlation), smoke spill fan flow test (verify each fan delivers the design flow), FFC panel functional test (simulate fire detector activation and verify the response sequence within design timing), fire damper closure test (verify each damper closes on signal within tolerance), and overall smoke spill drill (verify the integrated system response under simulated fire scenario). The drill records form part of the AS 1851 compliance documentation maintained by the tunnel operator and reviewed by the building certifier or the fire engineering consultant on annual inspection.

Tunnel control centre — Transurban Operations, ASHRAE TC 9.9 Class A1, 24/7 staffed

The tunnel control centre is the twenty-four-hour staffed facility that monitors the tunnel network in real time and coordinates the emergency response. Transurban operates the Australian network from operations centres in Sydney (the M5 control centre handles the WestConnex network and the M5 East Tunnel), Melbourne (the Northbridge operations centre handles CityLink and West Gate Tunnel) and Brisbane (handles Clem7, AirportLinkM7 and Legacy Way). The state road authorities (NSW RMS/TfNSW, VicRoads, QLD TMR) operate their own traffic management centres that coordinate with the tunnel operator centres on cross-network incidents and traffic management.

Control centre HVAC — ASHRAE TC 9.9 Class A1

The tunnel control centre HVAC is engineered to ASHRAE Technical Committee 9.9 Class A1 climate standards — 22 to 27 degrees Celsius dry bulb temperature, 8 to 90 percent relative humidity (with the practical design target at 50 percent RH plus or minus 10), MERV 11 to MERV 13 filtration on the supply, ESD-safe construction throughout including bonded conductive flooring, raised floor or ceiling void cable management, dedicated UPS-backed power for the critical IT equipment and the SCADA workstations. The cooling capacity is sized to N+1 redundancy — at least one spare CRAC (computer room air conditioner) unit beyond the design load — so that maintenance or failure on one unit does not compromise the climate condition. The fresh air supply for the operator and analyst staff occupies a separate supply path with AS 1668.1 acceptable indoor air quality compliance.

SCADA and tunnel management systems

The tunnel SCADA monitors CO, NO2, visibility, traffic flow (loop detectors and CCTV cameras at typically 100 metre spacing), fire detection (linear heat detection cable along the tunnel ceiling), vehicle detection (overhead radar and AVI Automatic Vehicle Identification at the toll gantries), and the status of every jet fan, smoke spill fan, vent stack fan, damper, supply fan and FFC panel across the network. The operations centre operators have full visibility of the network state and can switch jet fan direction, ramp fan speed, activate smoke spill manually, dispatch incident response, alert emergency services and coordinate traffic management with the state road authority.

Toll gantry and AVI Automatic Vehicle Identification — Linkt, E-Toll Roam

The toll gantry scope sits at the tunnel portals and along the open road sections of the Transurban and ConnectEast networks. Each gantry holds the AVI Automatic Vehicle Identification cameras (number plate recognition cameras), transponder readers for the Linkt and E-Toll Roam electronic toll tags, and the lane and overhead variable message signs. The gantry HVAC scope is small — climate-controlled enclosures for the camera and the electronics — but the integration with the toll operations system carries data privacy and Privacy Act compliance obligations.

The toll gantry HVAC enclosure is typically a SBKJ SBAL-V galvanised G275 ductwork supplying a small dedicated chiller and supply fan for the camera and electronics enclosure. The enclosure is ESD-safe (bonded conductive flooring or floor mat, ESD-controlled work area) for the electronic equipment. The connectivity backhaul to the operations centre is via fibre optic cable with ACMA-licensed redundant 4G or 5G as the backup path. The Linkt by Transurban toll system covers the WestConnex, NorthConnex, M2, M5 East, M5, M7, M8, Eastern Distributor, Lane Cove Tunnel, Cross City Tunnel, Hills M2, Sydney Harbour Tunnel, CityLink, West Gate Tunnel, Clem7, AirportLinkM7, Legacy Way, M6 and M4 Tunnel networks across Sydney, Melbourne and Brisbane. E-Toll Roam is the alternative toll tag issued through state road authorities (NSW Roam, VicRoads E-Way) that operates across the same gantry infrastructure.

Underground carpark HVAC — Crown Casino, MCG, Optus Stadium, Adelaide Oval, Sydney Olympic Park

Underground carpark HVAC at the major Australian commercial and sporting venues shares the design framework with road tunnel ventilation but at smaller scale and lower fire-rating tier. The AS 1668.2 baseline ventilation rate is 1 litre per second per square metre of floor area (approximately 6 air changes per hour at 2.4 metre ceiling height), raised to 2 to 5 litres per second per square metre in diesel-vehicle dwell zones and entry/exit ramps. CO sensors at typically 25 to 50 metre grid spacing drive demand-controlled ventilation with variable speed jet fans. The CO cap is 30 ppm STEL with engineering target 25 ppm per AS 1668.2, and the NO2 cap is 3 ppm.

Major Australian underground carpark venues

The major Australian underground carpark venues include the casinos and entertainment precincts (Crown Casino Melbourne basement, Crown Sydney basement at Barangaroo, The Star Sydney), the major sporting venues (MCG basement, Marvel Stadium formerly Etihad, Optus Stadium Perth, Adelaide Oval, Sydney Olympic Park P1 through P14), the convention centres (BCEC Brisbane Convention and Exhibition Centre, Adelaide Convention Centre, Melbourne Convention and Exhibition Centre, ICC Sydney), the major shopping centres (Westfield network, Chadstone Melbourne, Eastland, Pacific Fair, Robina), the major commercial towers (IFC International Finance Centre, Aurora Place, Quay Quarter Tower, Atlassian HQ at Central Station Sydney), and the airport long-stay carparks (Sydney Airport, Melbourne Airport, Brisbane Airport, Perth Airport).

Jet fan layout in basement carpark

Most modern Australian basement carparks use a jet-fan ducted system rather than a fully-ducted ventilation grid. Jet fans 200 to 450 millimetre diameter at 6 to 12 metres per second discharge velocity are arranged in a herringbone or longitudinal pattern across the carpark soffit, with supply air entering one end through a galvanised SBAL-V auto duct line riser and exhaust risers at the opposite end via SBTF-2020 large diameter spiral or rectangular duct. The jet fan housings are stitchwelded on the SBKJ SB-ZF1500 stitchwelder for tight pressure rating, and the supply and exhaust ducts are fabricated on the SBAL-V auto duct line for high throughput on galvanised G275 service.

AS 1668.3 zoned smoke control in basement carparks

AS 1668.3 (Mechanical Smoke Control Systems Using Active Smoke Exhaust) governs the zoned smoke control approach in basement carparks. On fire detection in a smoke zone, the mechanical ventilation system switches to smoke-clearance mode at approximately 6 air changes per hour with positive pressure on adjacent stair pressurisation (50 Pa per AS 1668.1). Jet fans reverse or align to drive smoke toward an emergency exhaust outlet, with smoke spill ductwork rated to 250 degrees Celsius for 2 hours per AS 1530.4. Lift lobby pressurisation (Type C) and stair pressurisation operate on isolated supply ductwork. The TDF flange forming on the SBKJ SBAL-V achieves the tight-leakage Class C performance required for the pressurisation calculation.

Cross-passage emergency exit and pressurisation

Every modern Australian road tunnel has emergency cross-passages between the parallel tubes at typically 100 to 250 metre spacing. The cross-passage is the evacuation pathway for tunnel users to escape from a fire-affected tube into the parallel safe tube, with pedestrian doors and dampers controlling the air movement between the tubes. The cross-passage HVAC scope is pressurisation under AS 1668.3 zoned smoke control — the cross-passage is held at positive pressure relative to the fire-affected tube so that smoke cannot ingress through the open door during evacuation. The pressurisation supply duct is on a dedicated supply fan, fabricated in galvanised G275 on the SBKJ SBAL-V auto duct line, fire-rated to AS 1530.4 at 250 to 400 degrees Celsius 2 to 4 hour duration.

NFPA 502 also covers the cross-passage design — the standard requires evacuation pathways at sufficient spacing that tunnel users can reach a safe refuge within typically 5 minutes of the fire incident. The cross-passage door is fire-rated and self-closing, with the dampers in the supply duct positioned to maintain the pressurisation differential through the evacuation period. The fire engineering consultant runs the smoke and tenability calculation to verify the cross-passage design meets the NFPA 502 evacuation timing target.

Equipment room — diesel generator, switchroom, UPS, battery, AS/NZS 5139 Li-ion

The tunnel equipment room scope handles the standby power, the switchroom, the UPS, the battery bank, the automatic transfer switch (ATS) and the lighting and ventilation power distribution. The diesel generator is typically a 500 to 2000 kilowatt unit on standby for the tunnel ventilation fans, the SCADA, the lighting and the fire-life-safety systems. The generator radiator exhaust duct is heavy gauge galvanised or carbon steel, fabricated on the SBKJ SBLR-600 longitudinal seam welder and the SBAL-V auto duct line, with AS/NZS 60079 Zone 2 hazardous area classification at the generator fuel handling and exhaust point.

The battery bank scope on modern tunnels increasingly includes lithium-ion battery for the UPS and the standby power, with AS/NZS 5139 (Electrical Installations — Safety of Battery Systems for Use with Power Conversion Equipment) governing the safety requirements including thermal runaway risk mitigation. The battery room is typically Zone 2 for hydrogen off-gas (1.25 percent of 25 percent LEL detection threshold) with dedicated extract and rapid shutdown logic. The battery room HVAC duct is on the SBKJ SBAL-V in galvanised G275 with spark-resistant fan and IECEx Ex-d motor specification for the dedicated extract path.

NFPA 130 fixed guideway transit — Cross River Rail, Sydney Metro, Melbourne Metro Tunnel adjacencies

NFPA 130 (Standard for Fixed Guideway Transit and Passenger Rail Systems) governs the rail tunnel ventilation and passenger life safety scope, which is the framework for the adjacent rail tunnel projects that interface with the road tunnel network at several points. Cross River Rail in Brisbane (opening 2026, dual rail tunnel under the Brisbane River and the CBD, PULSE JV — CPB, UGL, John Holland) interfaces with the Brisbane road tunnel network at the Clem7, AirportLinkM7 and Legacy Way crossing points. Sydney Metro (NorthWest, City and Southwest, Western Sydney Airport) interfaces with the Sydney road tunnel network at the Harbour Tunnel, Lane Cove and Eastern Distributor crossover points. Melbourne Metro Tunnel interfaces with CityLink at the Burnley Tunnel crossover.

The combined fire engineering across the rail tunnel and the adjacent road tunnels requires coordinated emergency ventilation response with both NFPA 502 (road) and NFPA 130 (rail) scenarios resolved. The HVAC duct designer working on either side of the interface coordinates with the other side to verify the smoke spill, pressurisation and evacuation pathway designs do not conflict. The Mernda Rail Tunnel (Metro Trains Melbourne), the Geelong rail corridor, the Pakenham and Cranbourne rail extensions are the supporting Victorian rail tunnel scope. The Sydney Trains and NSW TrainLink networks provide the broader rail context for the Sydney road tunnel interfaces.

Major Australian road tunnel construction Tier 1 JV — John Holland, Lendlease, Acciona, Bouygues, Webuild, Multiplex

The Tier 1 construction Joint Ventures bidding into and delivering Australian road tunnel projects include John Holland CIMIC (ASX:CIM, the largest Australian tunnelling contractor with NorthConnex, Clem7, Legacy Way, Cross River Rail, Sydney Metro and Melbourne Metro Tunnel on the recent project list), Lendlease (major Australian contractor with Cross Yarra Partnership Melbourne Metro Tunnel and several road tunnel projects), Acciona (Spanish-origin with Australian tunnelling operations on WestConnex, M6 and Western Harbour Tunnel), Bouygues (French-origin with Australian tunnelling operations on Melbourne Metro Tunnel and Sydney Metro), Ferrovial (Spanish-origin with Australian operations), Salini Impregilo / Webuild (Italian-origin with Snowy 2.0 and several Australian tunnel projects on the recent list), Multiplex (Brookfield, major Australian contractor), McConnell Dowell (NZ-based with TBM tunnel experience across ANZ) and BMD Construction (Australian civil contractor).

The HVAC duct package for each road tunnel sits within the Tier 1 JV's mechanical services scope, with the duct fabrication typically subcontracted to an HVAC duct fabricator who manufactures to the JV's design specification. The duct fabricator typically operates SBKJ machinery — the SBAL-V auto duct line for the bulk rectangular duct, the SBTF spiral tubeformer range for the round duct, the SBSF-1525 slitter and SBPC1500 plasma cutter for the heavy gauge plate preparation, the SB-ZF1500 longitudinal stitchwelder for the welded plenum sections and the SBLR-600 inverter welder for the field installation welding. The Tier 1 JV engineering team coordinates the HVAC duct package against the structural design, the fire engineering design, the tunnel ventilation engineering design and the mechanical/electrical services design.

State road authorities, industry bodies and PIARC

The state road authorities are the regulatory and procurement bodies for the Australian road tunnel network:

• NSW RMS / TfNSW — Transport for NSW (formerly Roads and Maritime Services), the NSW state road authority. Responsible for the NSW road tunnel licensing, EPA condition interface, and the operational standards for the Sydney road tunnel network.
• VicRoads / DoT Victoria — the Victorian state road authority, formerly VicRoads, now the Department of Transport Victoria. Responsible for the Victorian road tunnel licensing and the operational standards for the Melbourne road tunnel network.
• QLD TMR / DTMR — Department of Transport and Main Roads Queensland. Responsible for the Queensland road tunnel licensing and the operational standards for the Brisbane road tunnel network.
• Main Roads WA — the Western Australia state road authority.
• DPTI SA — Department of Planning, Transport and Infrastructure South Australia.
• TasRoads — the Tasmania state road authority.
• Roads ACT — the Australian Capital Territory road authority.
• NTG Transport — Northern Territory Government Transport.

The industry bodies and peak associations include:

• AustRoads — the peak Australian and New Zealand road authority, a collaboration of the Commonwealth, state and territory road and transport agencies. Publishes the AustRoads Guide to Road Tunnels which is the primary Australian reference for tunnel ventilation design, fire and life safety, emergency ventilation and the interface with the state road authorities. AustRoads has a Tunnel Ventilation Group that develops the strategic guidance.
• Australasian Tunnelling Society (ATS) — peak Australian tunnelling industry body and a sub-group of Engineers Australia. Publishes guidance notes on tunnel ventilation, fire and life safety, shaft sinking and tunnel operations.
• International Tunnelling and Underground Space Association (ITA) — global peak body for tunnel construction and operation.
• PIARC World Road Association — global peak body for road authorities. Technical Committee D5 (Road Tunnels Operation) publishes the strategic tunnel ventilation guidance referenced worldwide.
• Transurban Linkt — Transurban toll road operations.
• AHIA Australian Highways and Infrastructure Industry — industry body.
• Bus Industry Confederation BIC — bus industry body, supporting reference for the heavy vehicle exhaust characterisation in tunnel design.
• NHVR National Heavy Vehicle Regulator — heavy vehicle regulator, supporting reference for the heavy vehicle traffic loading in tunnel design.
• ASIO, AFP, counterterrorism agencies — supporting reference for the tunnel security scope including overhead surveillance, vehicle screening at portals and emergency response coordination.

SBKJ ductwork by tunnel application — material, gauge, machine

The SBKJ ductwork specification for an Australian road tunnel HVAC package breaks down by application zone:

Tunnel make-up air and ventilation supply — galvanised G275 1.2 to 1.6 mm on SBAL-V

The tunnel make-up air and ventilation supply duct serves the clean make-up air path from the surface intake to the tunnel ceiling supply terminals. The duct sees clean filtered make-up air and does not see corrosive exhaust gas, so galvanised G275 at 1.2 to 1.6 millimetre is appropriate. The SBKJ SBAL-V auto duct production line fabricates this duct at high throughput, with the configurations matched to the duct gauge and pressure class. The SBAL-V produces continuous duct length with TDC or TDF transverse joint, S-cleat or drive cleat longitudinal joint and Pittsburgh corner lock, achieving SMACNA medium pressure class which is the standard for tunnel make-up air service.

Vent stack interior lining — 316L stainless 1.6 to 3.0 mm on SBAL-V and SB-ZF1500

The vent stack interior duct lining is 316L stainless welded construction at 1.6 to 3.0 millimetre gauge. The SBKJ SBAL-V auto duct line in 316L stainless configuration fabricates the rectangular sections, and the SBKJ SB-ZF1500 longitudinal stitchwelder welds the seam to achieve the medical-grade integrity required for the corrosive exhaust gas service. The heavy gauge plate above 3 millimetre is cut on the SBPC1500 plasma cutter and welded with the SBLR-600 inverter welder using ER316L stainless filler wire per AS/NZS 1554.6 stainless welding qualification. The same machine combination handles the chemical scrubber and activated carbon plenum sections.

Tunnel control room and operations centre — 316L stainless 1.0 to 1.2 mm

The tunnel control room and operations centre ASHRAE TC 9.9 climate-controlled spaces use 316L stainless at 1.0 to 1.2 millimetre gauge on the SBKJ SBAL-V auto duct line in stainless configuration. The lighter gauge reflects the cleaner duty (no corrosive exhaust gas, controlled IAQ) but the stainless choice protects against coastal atmospheric exposure at sites near Sydney Harbour, the Brisbane River and Port Phillip Bay.

Carpark recirculation and jet fan extraction — spiral on SBFB-1500 and SBTF range

The carpark recirculation duct and the jet fan extraction duct are spiral round duct on the SBKJ SBFB-1500 spiral fitting machine and the SBTF range (SBTF-1500, SBTF-1602, SBTF-2020). The SBSF-1525 spiral former produces the spiral seam. Diameter ranges from 600 millimetre for individual jet fan plenum connections to 2000 millimetre for primary recirculation risers. Material is galvanised G275 at 1.2 to 1.6 millimetre.

Smoke spill duct fire-rated 250 to 400 degrees C 2 to 4 hours — heavy gauge on SBSF-1525, SBPC1500, SB-ZF1500

The smoke spill ductwork is heavy gauge galvanised or carbon steel at 2.0 to 4.0 millimetre. The SBKJ SBSF-1525 slitter prepares the plate stock from coil at the design width, the SBPC1500 plasma cutter cuts the plate for transitions and access panels, and the SB-ZF1500 longitudinal stitchwelder welds the seam to achieve the AS 1530.4 fire-rated furnace test pass at 250 to 400 degrees Celsius for 2 to 4 hours. Transverse joints use intumescent gasket. Fire dampers per AS 1530.4 at every fire compartment boundary.

Jet fan ductwork and vent stack 80 to 100 m — manual and plasma SBPC1500, AS 1530.4 certified

The jet fan ductwork manual fabrication and the vent stack 80 to 100 metre rigid duct sections use the SBKJ SBPC1500 plasma cutter for the heavy gauge plate preparation and the SBLR-600 inverter welder for the field installation welding. The complete assembly is AS 1530.4 fire-rated certified through the furnace test on the first-of-type duct sections.

Workplace exposure standards in vehicle tunnel atmospheres — CO 25, NO2 3, DPM 0.1, PM2.5 10

The workplace exposure standards that the road tunnel HVAC engineer designs against are issued by Safe Work Australia and the AS 1668.2 engineering caps. The AS 1668.2 caps are tighter than the Safe Work Australia STEL because the tunnel population includes commuters who lack the occupational training and PPE that an industrial worker would carry, so the engineering design point sets a lower trigger threshold.

Carbon monoxide CO — 30 STEL, 50 PEL, AS 1668.2 cap 25

Carbon monoxide is the killer in vehicle exhaust. The hazard is acute — CO binds to haemoglobin with 250 times the affinity of oxygen and displaces oxygen from the blood, causing rapid asphyxiation at concentrations as low as 200 to 400 parts per million for short exposure. The Safe Work Australia exposure standard is 30 parts per million STEL with 50 parts per million peak excursion limit. The AS 1668.2 carpark and tunnel engineering cap is 25 parts per million which is the design trigger for the demand-controlled ventilation response. CO is the design driver in low-speed congestion and exit-ramp accident scenarios where stationary vehicles dump exhaust into a fixed tunnel cross-section without forward air movement to dilute the exhaust.

Nitrogen dioxide NO2 — 5 STEL, AS 1668.2 cap 3

Nitrogen dioxide is the diesel exhaust marker — diesel vehicles emit significantly more NOx (NO and NO2) than petrol vehicles, and NO2 is the irritant component that affects the respiratory system. The Safe Work Australia exposure standard is 5 parts per million STEL and the AS 1668.2 cap is 3 parts per million. NO2 is also the primary source of the nitric acid in tunnel exhaust gas that attacks the vent stack interior duct lining.

Diesel particulate matter DPM — 0.1 mg/m³ EC, ultrafine PM2.5 10

Diesel particulate matter at the 0.1 milligrams per cubic metre elemental carbon limit is the tunnel commuter exposure risk — ultrafine particles that pass into the deep lung. IARC classifies diesel engine exhaust as Group 1 carcinogen (same hazard class as asbestos). PM2.5 (particulate matter under 2.5 micrometre aerodynamic diameter) is 10 milligrams per cubic metre acute and PM10 is 20 milligrams per cubic metre inhalable. General inhalable dust is 50 milligrams per cubic metre. The tunnel commuter exposure on a typical urban commute (30 to 60 minutes per day in tunnel) is well below the acute exposure limit but the cumulative exposure across a working life is a concern.

Other vehicle exhaust components — CO2, benzene, SO2

CO2 at 5000 parts per million TWA matters in stationary congestion where vehicle exhaust accumulates and forward air movement is absent. Benzene from petrol fume vapour at 1 part per million STEL matters within service station forecourt zones adjacent to tunnel portals (AS/NZS 60079 Zone 2 within the forecourt). SO2 sulfur dioxide at 2 parts per million STEL matters historically with heavy fuel oil but is rare in modern Australian vehicle traffic following the introduction of ultra-low-sulphur diesel and the phase-out of leaded petrol.

Emergency fire scenario hazards — HCN, HF, PCB, halogenated combustion product

The emergency tunnel fire scenario introduces additional hazards from the burning vehicle interior. Hydrogen cyanide HCN at 5 parts per million STEL is generated from nitrogen-containing polymers in vehicle interior trim and seating. Hydrogen fluoride HF at 1.8 parts per million STEL is generated from fluorinated polymers (PTFE, PVDF) in vehicle wiring and trim. Polychlorinated biphenyl PCB and chlorinated halogenated combustion products are generated from chlorinated polymers (PVC) in vehicle wiring and trim. The fire engineering consultant accounts for these hazards in the tunnel fire scenario response design, with the smoke spill and evacuation pathway sized to clear the toxic combustion products within the tenability timing.

Formaldehyde, methane and refrigerant — rare scenarios

Formaldehyde at 1 part per million STEL is rare in tunnel atmosphere except in the emergency fire scenario where furniture and MDF combust. Methane at 1.25 percent LEL is rare except in LPG vehicle and sewer-adjacent scenarios. R32, R454B and R744 refrigerants are present in the tunnel control room cooling system only and are not a tunnel atmosphere concern except in a major refrigerant release scenario.

Construction phase versus operating phase — adjacent scope

This guide covers the operating phase of road tunnel HVAC — the in-service ventilation, vent stack, smoke spill and control centre scope across the asset operating life. The construction phase scope is the TBM tunnel boring machine construction HVAC scope which is covered in the TBM tunnel boring machine construction HVAC duct guide. The construction phase covers the TBM operator cab, the gantry crew compartment, the tunnel face ventilation via lay-flat ducting, the shaft sinking ventilation, the shotcrete plant local exhaust and the refuge chamber HVAC — different applications under different standards (AS 2865 confined spaces and AS 1746 confined space air monitoring) that precede the operating phase scope covered in this guide.

The same Tier 1 JV contractors often deliver both the construction phase and the operating phase HVAC scope on the same project, but the engineering teams are usually different — tunnelling engineering for construction, building services engineering for operation. The HVAC duct fabricator may produce duct for both phases, with the construction phase using SBKJ machinery in heavy-gauge stainless and galvanised configurations for the TBM-mounted scope, and the operating phase using the same machinery for the vent stack, smoke spill, jet fan plenum and control centre scope. The transition from construction to operation happens at TBM breakthrough and the progressive commissioning of the operating-phase systems through the project handover.

Procurement timeline for an operating road tunnel HVAC duct package

The procurement timeline for an operating road tunnel HVAC duct package runs 24 to 48 months from contract award to final delivery and commissioning, with the timeline driven by the tunnel construction sequence and the staged commissioning of the operating-phase systems.

• Months 0 to 6 — Contract award and engineering coordination. Detailed shop drawing development, coordination with the Tier 1 JV engineering team, sign-off on duct routing through the planned tunnel alignment, fire engineering basis lock-down, material specification confirmation (galvanised G275 for make-up air supply, 316L stainless for vent stack interior and chemical scrubber, heavy gauge fire-rated for smoke spill), hazardous area classification confirmation under AS/NZS 60079.10.1 at the diesel generator, battery room and adjacent service station forecourt.
• Months 6 to 12 — First-of-type and Factory Acceptance Test. Manufacture of first-of-type duct sections including the 316L stainless welded vent stack interior lining sample, the fire-rated smoke spill duct furnace test sample (witnessed by accredited fire engineering laboratory under AS 1530.4), the jet fan plenum first article. FAT witnessed by the principal contractor's engineering representative or by the project ventilation engineer.
• Months 12 to 24 — Bulk fabrication. High-throughput fabrication of the bulk main and auxiliary duct on the SBAL-V auto duct line for galvanised and stainless service, the SBSF-1525 slitter and SBPC1500 plasma cutter for the heavy gauge smoke spill plate preparation, the SB-ZF1500 stitchwelder for welded plenum sections, and the SBTF range and SBFB-1500 for the spiral duct production. Continuous QA witnessed at the fabricator, mill certificates collected on 316L stainless duct, weld maps documented for fire-rated and stainless sections.
• Months 18 to 36 — Staged delivery. Phased delivery aligned to tunnel construction progress and operating system commissioning sequence. Vent stack scope during portal works, jet fan plenum during ceiling installation, smoke spill duct during fire engineering work front, control room scope during tunnel commissioning, carpark scope during the connected commercial venue construction.
• Months 30 to 42 — Installation and commissioning. Duct installation, pressure and leakage testing per AS 4254 class C or D, jet fan thrust verification, smoke spill flow verification, vent stack fan curve verification, EPA stack emission monitoring calibration, FFC fire fan control panel functional test, AS 1851 baseline maintenance schedule establishment, hazardous area dossier sign-off, fire damper integration test.
• Months 42 to 48 — Tunnel operator handover. Final acceptance, as-built drawing handover, fan curves, leakage test certificates, fire-rated assembly furnace test certification, smoke spill drill records, jet fan thrust test records, vent stack EPA emission monitoring records, AS 1851 maintenance baseline. The tunnel operator (Transurban, ConnectEast, QLD Tollway, Queensland Motorways or the state road authority) takes ongoing responsibility for the operating asset.

Commissioning — jet fan thrust test, smoke spill drill, vent stack EPA calibration

Road tunnel HVAC commissioning is a multi-stage process running over several months and culminating in the tunnel operator's handover and the road tunnel opening. The commissioning sequence ties back to the more general framework covered in the HVAC commissioning and air balancing guide, with specific additions for the tunnel context.

The first stage is component commissioning — fan startup against design fan curve, damper actuation testing, sensor calibration (CO, NO2, visibility, fire detection), leakage testing of installed duct sections to AS 4254 class C or D, and verification of fail-safe positions on power loss and fire alarm signal. The second stage is sub-system commissioning — jet fan thrust verification (each fan delivers 300 to 700 Newtons of thrust at the design speed via Pitot tube discharge velocity measurement and motor electrical input correlation), smoke spill fan curve verification on the installed duct system, vent stack fan curve verification, FFC fire fan control panel functional response within 30 seconds of fire detector activation, vent stack EPA stack emission monitoring calibration to the NSW EPA, VIC EPA or QLD DES approved methods. The third stage is integrated system testing — coordinated response to simulated fire alarm and CO trip signals from the tunnel SCADA, verification of jet fan direction switch in fire mode, validation of pressure profile and air-flow direction across the full tunnel system, and the AS 1851 smoke spill drill as the final acceptance.

The Factory Acceptance Test on first-of-type duct is the project-controlled document that ties the on-site commissioning back to the fabrication baseline. SBKJ supports witnessed FAT on first-of-type duct as standard, with full documentation including weld procedure qualification records under AS/NZS 1554.6 for stainless welding, weld inspector reports, mill certificates for 316L stainless raw material, dimensional inspection records, fire-rated assembly furnace test certification under AS 1530.4 and the AS 4254 leakage class verification.

Maintenance and inspection — AS 1851 annual schedule, jet fan thrust, smoke spill drill

Operating road tunnel HVAC maintenance follows the AS 1851 (Routine Service of Fire Protection Systems and Equipment) annual schedule, the AS 1668.2 vehicle tunnel ventilation engineering compliance schedule and the EPA stack emission monitoring schedule. The operator (Transurban, ConnectEast, QLD Tollway, Queensland Motorways or the state road authority) runs the annual cycle, with the maintenance contractor delivering the inspection, test and maintenance work to the AS 1851 schedule.

The annual cycle includes the jet fan inspection (visual inspection, thrust test, vibration measurement, bearing condition, acoustic measurement), the smoke spill activation drill (full functional test of the FFC panel and the integrated smoke spill response with simulated fire detector activation), the vent stack fan curve verification, the EPA stack emission monitoring calibration, the CO and NO2 sensor calibration and the fire damper functional test under AS 1530.4. Periodic shutdown and closure work includes the major inspection at typically 5-year intervals (more comprehensive duct inspection, structural inspection of the vent stack, replacement of consumables like fire damper fusible links and CO sensor heads) and the HVAC reverse flow direction test which verifies the bidirectional jet fan capability under the fire mode response logic.

SBKJ machine recommendation — by road tunnel HVAC application

The following machine recommendations cover the typical SBKJ portfolio for an Australian road tunnel HVAC duct fabrication shop. Each application has a primary machine and one or more secondary machines for fittings, accessories and field repair. The complete machine portfolio is documented on the SBKJ machine portfolio page with detailed specifications and capabilities.

Tunnel make-up air and ventilation supply (galvanised G275 1.2 to 1.6 mm)

• SBAL-V auto duct production line — primary machine configured for galvanised G275 construction at 1.2 to 1.6 millimetre for the tunnel make-up air supply and ventilation distribution duct. See the SBAL-V product page for full specifications.
• SBAL-III auto duct line — secondary machine for lighter gauge service in the carpark and amenity scope where standard SBAL-V galvanised configuration is the throughput requirement.

Vent stack interior lining and chemical scrubber (316L stainless 1.6 to 3.0 mm welded)

• SBAL-V auto duct production line — primary machine configured for 316L stainless construction for the vent stack interior lining, chemical scrubber plenum and activated carbon plenum sections.
• SB-ZF1500 longitudinal stitchwelder — primary machine for the welded longitudinal seam in 316L stainless to achieve the medical-grade integrity required for the corrosive exhaust gas service.
• SBPC1500 plasma cutter — secondary machine for the heavy gauge plate cutting above 3 millimetre.
• SBLR-600 inverter welder — secondary machine for field installation welding with ER316L stainless filler wire per AS/NZS 1554.6.

Tunnel control room and operations centre (316L stainless 1.0 to 1.2 mm)

• SBAL-V auto duct production line — primary machine in 316L stainless configuration for the ASHRAE TC 9.9 climate-controlled spaces and the coastal site exposure.

Jet fan ductwork and vent stack rigid duct (heavy gauge spiral and rectangular)

• SBTF-2020 spiral tubeformer — primary machine for 2000 millimetre primary vent stack and tunnel ventilation duct.
• SBTF-1602 spiral tubeformer — primary machine for 1500 to 1600 millimetre vent stack and jet fan ductwork.
• SBTF-1500 spiral tubeformer — primary machine for 600 to 1500 millimetre jet fan plenum and carpark recirculation duct.
• SBSF-1525 — primary machine for spiral seam production on the round duct and slitter for the smoke spill plate preparation.
• SBFB-1500 spiral fitting machine — primary machine for the jet fan and vent stack transitions and bell-mouth inlets.
• SBPC1500 plasma cutter — secondary machine for plasma cutting of heavy-gauge plate for evasee transitions and silencer baffles.

Smoke spill duct fire-rated to 250 to 400 degrees C 2 to 4 hours (heavy gauge welded)

• SBSF-1525 slitter — primary machine for plate stock preparation from coil at the design width.
• SBPC1500 plasma cutter — primary machine for plate cutting for transitions and access panels.
• SB-ZF1500 longitudinal stitchwelder — primary machine for welded longitudinal seam to achieve the AS 1530.4 fire-rated furnace test pass.
• SBLR-600 inverter welder — secondary machine for field installation welding.

Carpark recirculation and jet fan extraction (galvanised spiral)

• SBFB-1500 spiral fitting machine — primary machine for the carpark recirculation duct fittings.
• SBTF-1500 / SBTF-1602 — primary machines for the carpark recirculation spiral duct.
• SBSF-1525 — primary machine for the spiral seam production.

Hazardous area service (Zone 2 at diesel generator, battery room, adjacent service station forecourt)

• Spark-resistant fans — typically aluminium impeller blades in a fibreglass-reinforced or stainless-steel casing, certified to AS/NZS 60079.1 (flameproof enclosures) and AS/NZS 60079.7 (increased safety).
• IECEx Ex-d ATEX motors — mandatory for the diesel generator Zone 2, battery room Zone 2 hydrogen off-gas, adjacent service station Zone 2 forecourt and any LPG forklift adjacent zone.
• Anti-static surface treatment on duct — specified at the order stage of the SBAL-V or SBTF production where the duct passes through a hazardous area zone.
• Bonding straps between duct sections and earth-grounding at intervals — verified by continuity resistance test below 10 ohms.

Related guides on SBKJ

This guide on road tunnel and major roads infrastructure HVAC duct sits alongside several related references on the SBKJ insights library:

• TBM tunnel boring machine construction HVAC duct guide — covers the construction-phase HVAC scope across the TBM operator cab, gantry crew compartment, tunnel face ventilation, shaft sinking, shotcrete plant, hyperbaric chamber and refuge chamber. The construction-phase scope precedes the operating-phase scope covered in this article.
• Multi-storey carpark, basement, automated parking, park-and-ride and EV charging carpark HVAC duct guide — covers the carpark ventilation scope at the commercial venues that interface with the underground carpark portion of this guide.
• Tier 1 construction major project motorway, rail and infrastructure HVAC duct guide — covers the surface construction scope at the launch shaft yard, batching plant, office and amenity that supports the tunnel construction.
• Fire and smoke damper HVAC duct integration — covers the AS 1530.4 fire-rated duct and AS 1851 damper specifications used at fire-rated boundaries throughout the road tunnel system.
• Welding methods for HVAC duct fabrication — covers the welded duct fabrication processes used for 316L stainless vent stack interior and heavy gauge smoke spill ductwork.
• HVAC commissioning and air balancing guide — covers the commissioning framework that the tunnel HVAC commissioning sequence extends.
• SBKJ machine portfolio — the full SBKJ duct fabrication machinery range.
• SBAL-V auto duct production line — the SBKJ machine used for rectangular road tunnel HVAC duct in galvanised G275 and 316L stainless configurations.
• Contact SBKJ — Box Hill North VIC engineering office.
• All insights articles — the full SBKJ engineering insights library.

FAQ

What Australian standards govern operating road tunnel ventilation and HVAC duct?

The binding framework is AS 1668.2 (mechanical ventilation including vehicle tunnel ventilation appendix with fresh air supply 1.0 to 1.5 cubic metres per second per traffic lane, CO cap 25 ppm and NO2 cap 3 ppm), AS 4254 (ductwork), AS 1530.4 (fire-rated assemblies including smoke spill duct at 250 to 400 degrees Celsius for 2 to 4 hours), AS 1668.1 (mechanical ventilation for acceptable indoor air quality including tunnel control centre), AS 1668.3 (zoned smoke control), AS/NZS 60079 (hazardous area at LPG forklift, diesel generator and battery rooms), AS 1851 (routine service), NCC Class 7a carpark, Class 8 industrial control centre, Class 10b non-habitable, AS 1735 lift, AS/NZS 1158 carpark and tunnel lighting and AS/NZS 1170.2 and 1170.4 wind and earthquake loading on vent stack. International references: NFPA 502 Road Tunnels (jet fan thrust, smoke spill direction, evacuation pressurisation, tunnel fire scenarios), NFPA 88A parking structure, NFPA 130 fixed guideway transit rail, PIARC World Road Association, AustRoads Guide to Road Tunnels and the state road authority engineering standards (NSW RMS/TfNSW, VicRoads/DoT Victoria, QLD TMR, Main Roads WA, DPTI SA, TasRoads, Roads ACT, NTG Transport).

What CO, NO2, particulate and other workplace exposure standards apply to a vehicle tunnel atmosphere?

CO 30 ppm STEL with 50 ppm peak excursion (AS 1668.2 engineering cap 25 ppm), NO2 5 ppm STEL (AS 1668.2 cap 3 ppm), CO2 5000 ppm TWA, benzene 1 ppm STEL (within service station forecourt zone AS/NZS 60079 Zone 2), diesel particulate matter 0.1 mg/m3 elemental carbon (DPM ultrafine PM2.5 10 mg/m3 acute), PM10 20 mg/m3, inhalable dust 50 mg/m3, SO2 2 ppm STEL (legacy heavy fuel oil), formaldehyde 1 ppm STEL (rare fire scenario), H2S 10/15 STEL (sewer adjacent), CH4 1.25% LEL (LPG vehicle, sewer adjacent), HCN 5 STEL (rare emergency fire), HF 1.8 STEL (rare emergency fire), PCB chlorinated halogenated combustion product (vehicle interior fire rare). The AS 1668.2 caps are tighter than Safe Work Australia STEL because the tunnel population includes commuters who lack the occupational training and PPE that an industrial worker carries.

How does a Transurban operated tunnel use jet fans for longitudinal ventilation?

Transurban (ASX:TCL) operates the majority of the Australian toll road tunnel portfolio — Sydney (NorthConnex, WestConnex Rozelle Interchange and M4-M5 Link and M4 and M8 Tunnels, Sydney Harbour Tunnel, M5 East, Cross City, Lane Cove, Eastern Distributor), Melbourne (West Gate, CityLink Burnley and Domain), Brisbane (Clem7, AirportLinkM7, Legacy Way), plus international assets in Washington DC and Montreal. The Transurban tunnel ventilation engineering uses longitudinal flow jet fans at the tunnel ceiling soffit to drive air in the direction of traffic flow. Jet fans are 600 to 1200 mm diameter axial fans with aluminium hub and stainless casing, fire-rated to AS 1530.4 at 250 to 400 degrees C for 2 to 4 hours, supplied by Colt, Greenheck, Twin City, Aerovent, Systemair, S&P Soler & Palau, Howden, Industrial Wind, Sahbox Ventilation, Pacific Ventilation, Aerofoil, Australian Made TVS and EBM-Papst. Each fan delivers 300 to 700 Newtons thrust. Fan spacing 80 to 150 metres. Critical velocity 2.5 to 3.0 metres per second to prevent back-layering of smoke. The Transurban Operations Centre at Northbridge Melbourne (CityLink) and at the M5 control centre Sydney (WestConnex) monitors CO, NO2, visibility, traffic flow, CCTV and fire detection.

How is the 80 to 100 metre vent stack at a modern Australian road tunnel specified?

Modern Australian road tunnel vent stacks are 80 to 100 metres above ground at the tunnel portal. Stack structural design follows AS/NZS 1170.2 wind, AS/NZS 1170.4 earthquake and AS 1170.5. Stack interior duct lining is 316L stainless welded construction because the exhaust gas chemistry includes nitric acid from NO2 dissolution and sulphuric acid from SO2 dissolution. Vent stack fan room at the base houses 4 to 12 axial fans in parallel each 1.5 to 3 metres diameter delivering 50 to 200 m3/s. Optional chemical scrubber or activated carbon emission control. EPA stack emission monitoring is mandatory in NSW (POEO Act administered by NSW EPA), VIC (Environment Protection Act administered by Victorian EPA) and QLD (Environmental Protection Act administered by QLD DES). Continuous CO, NOx, particulate, opacity and stack flow measurement at stack exit. Most visible Australian examples: Rozelle Interchange WestConnex vent stacks, NorthConnex Wahroonga vent stack, West Gate Tunnel vent stacks at Footscray and Yarraville, CityLink Burnley and Domain vent stacks, Clem7 vent stacks at Bowen Hills and Woolloongabba.

What smoke spill duct fire rating does AS 1530.4 and NFPA 502 require for road tunnel emergency ventilation?

Smoke spill ductwork is fire-rated to AS 1530.4 at 250 to 400 degrees Celsius for 2 to 4 hours. Lower 250 degrees C 2 hour rating is typical for underground carpark smoke spill where the design fire is a single vehicle (4 to 8 megawatt fire). Upper 400 degrees C 4 hour rating is typical for road tunnel emergency ventilation where the design fire is a heavy vehicle (30 megawatt) or tanker fire (100 megawatt) per NFPA 502. Smoke spill duct construction is heavy gauge galvanised or carbon steel 2.0 to 4.0 mm with welded longitudinal seam, transverse joint with intumescent gasket, fire dampers per AS 1530.4 at every fire compartment boundary and AS 1851 annual functional test. Duct lining and external insulation is calcium silicate, mineral wool or fire-rated board to achieve AS 1530.4 furnace test pass. FFC fire fan control panel activates smoke spill fan, opens smoke spill damper and closes supply damper on fire signal typically within 30 seconds of first fire detector activation. SBKJ recommends SBSF-1525 slitter and SBPC1500 plasma cutter for heavy gauge smoke spill duct fabrication, SB-ZF1500 longitudinal stitchwelder for welded seam, AS 1530.4 fire-rated certification of entire assembly.

What jet fan thrust is specified for the West Gate Tunnel and the WestConnex Rozelle Interchange?

Jet fan thrust on the West Gate Tunnel (Transurban, 2024 opening, John Holland CPB JV construction) and the WestConnex Rozelle Interchange (Transurban, 2023 opening, John Holland and CPB JV construction) is 300 to 700 Newtons per fan, with multiple fans in parallel. Each fan is 900 to 1200 mm diameter, axial flow, aluminium hub blades and stainless steel casing, fire-rated AS 1530.4 250 to 400 degrees C 2 to 4 hour duration. Fan motor 30 to 75 kilowatt squirrel cage induction motor with variable speed drive and bidirectional capability. Spacing 80 to 150 metres along tunnel ceiling. Critical velocity 2.7 to 3.0 metres per second for 4-lane tunnel with 30 MW design fire per NFPA 502. Total thrust 50 to 200 kilonewton across full tunnel length divided into number of fans in parallel.

How does underground carpark ventilation per AS 1668.2 differ from road tunnel ventilation?

Underground carpark ventilation per AS 1668.2 shares CO and NO2 control logic with road tunnel ventilation but at smaller scale. AS 1668.2 nominal carpark ventilation rate 1 litre per second per square metre floor area (approximately 6 air changes per hour at 2.4 metre ceiling height), raised 2 to 5 L/s/m2 in diesel-vehicle dwell zones and entry/exit ramps. CO cap 30 ppm STEL with engineering target 25 ppm per AS 1668.2. NO2 cap 3 ppm. Modern Australian basement carparks use CO-monitored demand-controlled ventilation with variable speed jet fans (Colt, Greenheck, Aerolite, Cyclonix, S&P, Aerovent) in herringbone or longitudinal soffit layout. SBAL-V galvanised duct riser supply, SBTF-2020 large diameter spiral or rectangular duct exhaust. In fire mode AS 1668.3 zoned smoke control jet fans switch to smoke clearance direction 6 ACH with positive pressure on adjacent stair pressurisation (50 Pa per AS 1668.1). Smoke spill ductwork 250 degrees C 2 hour AS 1530.4. Major venues: Crown Casino Melbourne, BCEC Brisbane, Optus Stadium Perth, MCG basement, Marvel Stadium, Adelaide Oval, Brisbane Convention Centre, Sydney Olympic Park P1-P14, Westfield, Chadstone, IFC, Aurora Place, Crown Sydney basement, Quay Quarter Tower, Atlassian HQ.

What is the role of PIARC and AustRoads in Australian tunnel ventilation engineering?

PIARC (World Road Association) is the global peak body for road authorities and publishes strategic tunnel ventilation guidance through Technical Committee D5 (Road Tunnels Operation) — tunnel ventilation, fire and life safety, vehicle exhaust dispersion, vent stack design, tunnel operations. AustRoads is the peak Australian and New Zealand road authority — collaboration of Commonwealth, state and territory road and transport agencies — and publishes AustRoads Guide to Road Tunnels covering ventilation design, fire and life safety, emergency ventilation and interface with state road authorities (NSW RMS/TfNSW, VicRoads/DoT Victoria, QLD TMR, Main Roads WA, DPTI SA, TasRoads, Roads ACT, NTG Transport). HVAC duct designer cross-references AustRoads, PIARC, AS 1668.2 vehicle tunnel appendix, AS 1530.4 fire-rated, NFPA 502 Road Tunnels, state road authority engineering standards. Supporting bodies: Australasian Tunnelling Society ATS (sub-group of Engineers Australia), International Tunnelling Association ITA, Tunnelling Forum, AusRAIL, AusIMM.

What SBKJ machines fabricate the heavy-gauge duct for an Australian road tunnel HVAC package?

SBAL-V auto duct production line fabricates rectangular duct in galvanised G275 for tunnel make-up air and ventilation supply scope and in 316L stainless for vent stack interior, chemical scrubber, activated carbon plenum and tunnel control room ASHRAE TC 9.9 climate-controlled spaces. SBSF-1525 slitter and SBPC1500 plasma cutter prepare heavy gauge plate for smoke spill duct fire-rated 250 to 400 degrees C 2 to 4 hours under AS 1530.4. SBTF-1500, SBTF-1602 and SBTF-2020 spiral tubeformers fabricate round duct 600 mm to 2000 mm diameter for jet fan ductwork, vent stack internal duct and primary supply and exhaust risers. SBFB-1500 spiral fitting machine produces transitions, bell-mouth inlets and carpark recirculation duct fittings. SB-ZF1500 longitudinal stitchwelder welds seam on heavy-gauge smoke spill duct, vent stack stainless lining and jet fan plenum sections. SBLR-600 inverter welder handles field installation welding with 316L stainless filler wire (ER316L per AS/NZS 1554.6). SBAL-III entry-level configuration for lighter gauge service in carpark and amenity scope.

How is Cross River Rail Brisbane interfaced with the Brisbane road tunnel network?

Cross River Rail in Brisbane is the new 5.9 kilometre dual rail tunnel under Brisbane River and CBD, opening progressively from 2026. Delivered by PULSE JV (CPB, UGL, John Holland) and Cross River Rail Delivery Authority on behalf of Queensland Government and Brisbane City Council. Governed by NFPA 130 (Fixed Guideway Transit and Passenger Rail Systems) for rail tunnel ventilation and passenger life safety — different code framework to NFPA 502 which governs road tunnels. Cross River Rail interfaces with Brisbane road tunnel network where rail tunnel passes beneath or alongside existing Clem7 (Transurban), AirportLinkM7 (Transurban) and Legacy Way (Transurban) road tunnels. Combined fire engineering requires coordinated emergency ventilation response with both NFPA 502 and NFPA 130 scenarios resolved. Sydney Metro (NorthWest, City and Southwest, Western Sydney Airport) and Melbourne Metro Tunnel face similar interface complexity at Burnley Tunnel CityLink crossover in Melbourne and at Sydney Harbour Tunnel and Lane Cove Tunnel crossings in Sydney.