Why does aerospace HVAC ductwork need 316L stainless in so many places where commercial HVAC uses galvanised?

Aerospace manufacturing concentrates chemistries that destroy zinc coatings within months and corrode 304 stainless within years. The chromate-sulphuric anodising line for aluminium 7075 and 2024, the chromate conversion coating tank, the cadmium and chrome plating shop, the isocyanate paint booth extract, and the JP-8 jet fuel system flush extract all release hexavalent chromium Cr(VI), sulphuric acid mist, chloride and reduced-sulphur species into the extract air stream. The Safe Work Australia Workplace Exposure Standard for Cr(VI) is 0.005 mg/m³ — one of the lowest exposure limits in the WES schedule — and the duct itself becomes part of the emission-control loop. 316L stainless with welded crevice-free seams, an internal pickle-passivation finish and external isolation from the building structure is the only construction class that survives 15 to 20 years of service in those streams. SBKJ supplies 316L variants of our SBAL-V auto duct line and the SB-ZF1500 stitchwelder specifically to serve aerospace plating, anodising and paint booth extract scope.

What is the difference between AS 9100, AS 9110 and AS 9120, and why do they matter to an HVAC contractor?

AS 9100 is the aerospace quality management system standard for organisations that design and manufacture products for the aviation, space and defence industry. AS 9110 is the parallel standard for maintenance, repair and overhaul (MRO) organisations — the certificated commercial MRO bases at Brisbane, Sydney, Avalon and Melbourne hold this. AS 9120 is the standard for aerospace distributors and stockists. An HVAC contractor is not itself manufacturing aircraft, but when working on the airside of an aerospace facility the contractor's processes feed directly into the customer's AS 9100 or AS 9110 audit. Foreign object debris (FOD) control on the contractor's installation crew, traceability of materials introduced into the controlled environment, and documented commissioning of clean room and paint booth airflows are all evidence requirements that the customer needs from the HVAC contractor. Boeing Materials Quality Standards and Airbus AIS standards add a further procurement layer on the materials and finishes side.

How is aluminium dust from aircraft skin machining handled under NFPA 660 and AS 3957?

Aluminium aircraft alloys 7075, 2024 and 2014 generate combustible dust when machined, drilled, sanded or polished. The dust has a deflagration index Kst in the 200+ range and is classified St3 — the highest combustibility class. AS 3957 governs combustible dust handling in Australia and NFPA 660 (formerly NFPA 484 for combustible metals) is the international reference. The HVAC duct response is multi-layered: spark-resistant fans throughout the dust collection train (no carbon steel impellers, no aluminium-on-steel rubbing contact), continuous metal duct with minimum static-dissipative path resistance, NFPA 68 explosion venting on collector inlets and on long horizontal duct runs, no flexible duct in the combustible-dust extract train, no internal duct linings that could harbour dust accumulation, and wet-collector dust collection rather than dry where the inventory exceeds the threshold quantity. The Safe Work Australia WES for respirable aluminium dust is 1 mg/m³ — the deflagration risk almost always governs the design before the inhalation risk does.

Why is an autoclave cure room engineered as a separate zone from the layup cleanroom?

Composite autoclaves cure prepreg components under combined pressure and temperature — 180–220 degrees C and 7–14 bar of nitrogen for typical aerospace epoxy systems. The autoclave itself is a pressure vessel inside a vault that has to manage four hazards simultaneously: heat rejection from the autoclave shell, nitrogen displacement of breathable air during normal operation, possible epoxy off-gassing in a failed-cure scenario, and the explosion-relief venting required if a curing run goes outside envelope. Putting that inside a Class 10,000 cleanroom would destroy the cleanroom envelope every cure cycle. The autoclave room is a separate AS 1668.2 mechanical ventilation zone with 6–10 air changes per hour, oxygen depletion monitoring (target 19.5 per cent O2 minimum at breathing height), heat extract at the autoclave headspace and emergency purge to clear nitrogen accumulation. The duct material is 316L stainless because hot epoxy off-gassing creates a corrosive mist in any failed-cure event.

What is the HVAC scope for a paint booth handling aircraft livery — isocyanate and CARC?

Aerospace paint booths spray polyurethane finishes — the Boeing white, Airbus blue, regional fleet liveries — using isocyanate hardener chemistry. Polyurethane isocyanate has a Safe Work Australia STEL (short-term exposure limit) of 0.005 ppm, equal in magnitude to the chrome plating Cr(VI) WES and one of the most dangerous airborne chemistries on any aerospace site. AS 4114 governs spray booth construction in Australia, NFPA 33 is the international reference. The design is downdraft — supply at the ceiling at low velocity, extract through a grating in the floor — with face velocity at the operator of 0.5 m/s minimum. Extract air passes through a paint-arrestor stage, an activated carbon stage and HEPA H13 before discharge. The duct is 316L stainless on the extract side because the isocyanate-bearing condensate that accumulates in the duct attacks galvanised steel and creates a downstream contamination path. Operators wear supplied-air respirators in the booth — the HVAC system protects the surrounding facility, not the painter. CARC (chemical-agent-resistant coating) work for legacy aerospace adds further isocyanate loading.

Insights · Aerospace & Aviation Manufacturing

Aerospace Component Manufacturing, Commercial Aircraft MRO, General Aviation Hangar and Helicopter Overhaul HVAC Duct Guide

A working reference for HVAC ductwork engineering in Australian aerospace component manufacturing, commercial aircraft maintenance repair and overhaul, general aviation hangars, helicopter overhaul facilities and aerospace composite manufacturing. Written from Box Hill North Victoria for mechanical consultants on Boeing Aerostructures Australia, Quickstep Holdings, Marand Precision Engineering, Qantas Engineering, Virgin Australia Maintenance, Hawker Pacific, Sikorsky Australia, Bell Australia, Royal Flying Doctor Service and CSIRO Aerospace Materials projects — with detailed treatment of hangar mechanical ventilation under NFPA 409, composite layup cleanrooms, autoclave cure zones, hexavalent chromium anodising extract, isocyanate paint booth design to AS 4114, and the aluminium-dust combustible hazard under NFPA 660 and AS 3957.

By SBKJ Engineering Team · Published May 15, 2026 · 36 min read · Reviewed by SBKJ QA & Engineering

Why aerospace HVAC is a different discipline to commercial mechanical services

A commercial office tower mechanical service is a comfort-and-ventilation problem with a fire-life-safety overlay. An aerospace manufacturing or MRO facility mechanical service is a worker-safety problem first, a product-quality problem second, an audit-evidence problem third, and a comfort problem only after those three are answered. The same cooling load on a 5,000 m² office building and a 5,000 m² aerospace component fabrication shop might both be 800 kW, but the duct system delivering it is engineered to entirely different criteria — different materials, different leakage classes, different commissioning regimes, different documentation, and different procurement paths.

The first dimension that separates aerospace HVAC from commercial is chemistry. An aerospace facility concentrates more individually-hazardous chemistries inside one building envelope than any other manufacturing category we work on. The chromate-sulphuric acid anodising line and the chromate conversion coating tank both release hexavalent chromium Cr(VI) at a Safe Work Australia Workplace Exposure Standard (WES) of 0.005 mg/m³ — one of the lowest exposure limits in the WES schedule, on par with cyanide and arsenic. The cadmium, chrome, nickel and copper plating shop adds further heavy-metal mist with the same engineering response — push-pull lip extract over every tank, packed-bed wet scrubber on the discharge, dedicated 316L stainless ductwork that no other process can share. The aircraft livery paint booth uses isocyanate polyurethane hardener with a STEL of 0.005 ppm — equal in magnitude to the chrome plating WES and one of the most dangerous airborne chemistries on any industrial site. And surrounding all of it is the day-to-day workshop chemistry — methyl ethyl ketone (MEK) at WES 200 mg/m³, isopropyl alcohol (IPA) at 400 mg/m³, acetone at 500 mg/m³, toluene at 50 mg/m³, xylene at 50 mg/m³, naphtha at 100 mg/m³, jet fuel JP-8 kerosene at 100 mg/m³ — all of which can drift between zones if the duct system is not carefully segregated.

The second dimension is combustible dust. Aircraft alloys 7075, 2024 and 2014 generate aluminium dust when machined, drilled, sanded, polished or sawn. The deflagration index Kst exceeds 200 bar·m/s in most aerospace alloy mixes, placing the dust in dust hazard class St3 — the highest combustibility class. Titanium is in the same category. The combination of a high-Kst combustible dust and the routine ignition sources present in any working aerospace shop (cutting tools, grinding wheels, electrical equipment, static discharge, hot work) makes NFPA 660 (the consolidated combustible dust standard, formerly NFPA 484 for combustible metals) and AS 3957 the dominant constraints on the dust extract design. Spark-resistant fans are mandatory throughout the extract train, NFPA 68 explosion venting protects collectors and long horizontal duct runs, flexible duct is prohibited in the combustible-dust train, internal duct linings are not permitted because they harbour dust accumulation, and the dust collector itself is normally a wet type rather than a dry filter cartridge collector if the dust inventory exceeds the threshold quantity.

The third dimension is the composite manufacturing chemistry. Carbon fibre prepreg, epoxy resin, MEK peroxide curing agents, polyurethane secondary bonding, and the post-cure trim-and-drill dust environment all generate streams that require engineering control. Carbon fibre respirable particulate has no formal Australian WES at present but is recognised as an irritant and a cancer risk — local exhaust ventilation with HEPA H13 filtration is the engineering control of record. Composite curing peroxides (MEK peroxide and benzoyl peroxide) are explosive in concentration and require dedicated storage ventilation and AS 1940 flammable liquid controls. And the autoclave cure environment itself runs at 180-220 degrees C and 7-14 bar nitrogen pressure — a separate engineering problem entirely from the layup cleanroom that feeds it.

The fourth dimension is the quality system overlay. Australian aerospace manufacturers and MRO bases hold AS 9100 (design and manufacture), AS 9110 (MRO) or AS 9120 (distribution) certification — the aerospace-specific quality management standards that flow down to every contractor working inside the facility envelope. An HVAC contractor on a Boeing Aerostructures Australia Port Melbourne installation or a Qantas Engineering Brisbane heavy-maintenance hangar is not itself building aircraft, but every process the contractor introduces — foreign object debris (FOD) control on the installation crew, materials traceability for the introduced ductwork, documented commissioning of paint booth face velocities and clean room airflows — becomes evidence in the customer's audit. Boeing Materials Quality Standards (BMQS) and Airbus AIS standards add further procurement-side requirements on the materials of construction. Australian-fabricated 316L stainless ductwork to the SBKJ specification with a traceable mill certificate and a documented pickle-passivation finish is acceptable on most of these projects; cheap imported stainless without traceable provenance is not.

The fifth dimension is the regulatory framework. Commercial MRO bases operate under CASR (the Civil Aviation Safety Regulations administered by CASA), specifically CASR Part 145 for approved maintenance organisations. International cross-recognition flows from EASA Part 145 (European) and the FAA Repair Station Certificate under FAR Part 145 (United States). The HVAC scope is not itself a CASR Part 145 deliverable, but the controlled environments — the paint hangar, the engine test cell, the avionics integration room, the composite repair area — are part of the certified maintenance facility scope. Any HVAC modification to those spaces is logged in the facility's continuing airworthiness management exposition or the equivalent CASR/EASA/FAA document, and the contractor providing the modification provides the technical evidence.

Facility types — what each one demands of the duct system

Australian aerospace and aviation facility design starts with the use-class. The HVAC duct demand differs by an order of magnitude across the categories below, and a single major aerospace site usually contains four to six of them in close proximity.

Aerospace component manufacturer

Aerospace component manufacturers fabricate aircraft structures and sub-assemblies for the airframe primes and the engine OEMs. Boeing Aerostructures Australia at Port Melbourne is the principal Australian example, producing moveable trailing edge and flap assemblies for the Boeing 787 Dreamliner and the upcoming 777X. The HVAC scope spans composite layup cleanrooms, autoclave cure rooms, 5-axis CNC machining bays for titanium and aluminium parts, aluminium sheet metal fabrication for skin panels, riveting and bonding cells, post-cure trim-and-drill stations and paint booth (for protective and primer coatings, with final livery applied downstream at the airline). The duct quantity in a single component manufacturer site of 30,000–60,000 m² spans 15,000–25,000 m² of fabricated sheet duct across the supply, return, exhaust, scrubber, dust extract and clean room paths. The material mix is heavily skewed to 316L stainless on the extract side because the chemistries downstream of every aerospace process are aggressive to galvanised steel.

Marand Precision Engineering at Tullamarine Victoria represents a related but narrower scope — precision aerospace machining for weapons load adapter components and other small-batch structural parts. The HVAC profile is dominated by the 5-axis CNC machining bay with coolant mist extract, the materials handling chemistry (cutting fluid storage, inspection chemistries) and the inspection and dimensional metrology room which requires tight thermal stability.

Aerospace composite specialist

Quickstep Holdings at Bankstown New South Wales is the principal Australian aerospace composite specialist, manufacturing carbon fibre composite components for the Boeing 787, Airbus A380 panels and a number of other commercial and defence programmes. The HVAC scope is dominated by the composite layup cleanroom (ISO 7 with HEPA supply, ESD protection, controlled temperature and humidity), the autoclave cure room (separate zone, 180-220 degrees C, 7-14 bar nitrogen), the prepreg storage and freezer area (controlled below 0 degrees C to preserve the prepreg shelf life), the post-cure trim-and-drill bay with HEPA dust extract, the bond room for secondary bonding operations with adhesive fume extract, and the NDT laboratory for X-ray, ultrasonic and dye penetrant inspection. The duct quantity per square metre of facility is the highest of any aerospace facility category because the cleanroom and the controlled chemistry zones impose tighter ventilation rates than a general manufacturing shop.

Commercial wide-body MRO

Qantas Engineering operates heavy-maintenance bases at Brisbane, Sydney Mascot, Melbourne Tullamarine and Avalon. Virgin Australia Maintenance operates principally at Brisbane. International operators including Star Aviation MRO operate at Sydney and Melbourne. These are 20,000–40,000 m² hangar facilities with continuous 24/7 operation, multiple parallel maintenance lanes, paint shops for full livery work, engine teardown and overhaul bays, avionics integration rooms, fuel system flush bays, tyre and wheel shops and substantial accommodation and office wings. The HVAC duct scope per square metre is lower than a component manufacturer because most of the floor area is the hangar itself, but the absolute duct quantity in a single wide-body MRO base runs to 30,000-50,000 m² of fabricated sheet. The material mix is dominated by hot-dip galvanised G275 for the hangar and accommodation portions, with 316L stainless concentrated in the paint shop, engine test cell, fuel flush bay and any plating or chemical processing areas.

General aviation hangar

General aviation hangars at Bankstown New South Wales, Moorabbin Victoria, Archerfield Queensland, Jandakot Western Australia and Parafield South Australia host Cessna and Cirrus piston aircraft (distributed through Hawker Pacific and Cirrus Australia respectively), Diamond Aircraft from the Austrian distributor, light helicopters (Robinson Australia, Bell Australia under Babcock ownership), and corporate jets. The hangar is typically a single-storey clear-span shed of 1,000-4,000 m² with a small ancillary office and pilot facility. The HVAC scope is dominated by the hangar door air seal in fire mode, general maintenance bay ventilation at AS 1668.2 commercial industrial rates, intermittent fuel system flush extract during scheduled events, and minor exhaust on battery and oxygen system servicing. The duct quantity in a single general aviation hangar is 200-500 m² of fabricated sheet — one to two orders of magnitude smaller than a commercial wide-body MRO.

Helicopter overhaul facility

Helicopter overhaul facilities cover Sikorsky Australia (Lockheed-acquired, Sydney and Brisbane), Bell Helicopter Australia (now Babcock-owned), the Royal Flying Doctor Service helicopter and fixed-wing fleet (national and state operations), Toll Aviation (helicopter and medivac), CareFlight, Westpac Lifesaver and the various corporate operators (BHP Air, Rio Tinto Air, Network Aviation). The HVAC scope is hangar-driven but on a smaller volume than commercial MRO — typically 3,000-12,000 m² per facility. The chemistry mix is interesting because helicopters concentrate gearbox lubricant work, hydraulic system bleed, rotor blade dynamic balancing and engine teardown in a smaller envelope than a fixed-wing MRO — the duct extract paths overlap and have to be carefully segregated.

Aerospace research and government laboratory

CSIRO Aerospace Materials (within the CSIRO Manufacturing portfolio) and the Royal Aeronautical Society Australian Division research network operate a different facility profile — smaller floor area, higher chemistry concentration, more diverse process mix, and stricter audit requirements. The HVAC scope is dominated by fume cupboard exhaust, controlled environmental test chambers (temperature ranges from -55 degrees C to +85 degrees C for aircraft component testing), environmental stress screening (vibration plus thermal plus altitude), and small-scale composite and metallic fabrication for prototype manufacturing.

Engine test cell and engine MRO

Engine MRO covers the major commercial engine families (CFM56, V2500, Trent, GE family) at Qantas Engineering and selected international operators. Engine test cells are specialised facilities for sea-level static testing of overhauled engines, with massive heat rejection (10-50 MW thermal load during a test run), acoustic isolation requirements (the test cell wall has to reject 130-140 dB to maintain external compliance) and a distinct fire compartment under NFPA 415 fuel-handling logic. The HVAC duct scope is dominated by the high-temperature exhaust stack (316L stainless throughout, often with refractory lining for the hottest section near the engine), intake silencing for the test airflow that feeds the engine inlet, and operator gallery ventilation at AS 1668.2 commercial rates.

Australian operators and where the HVAC demand sits

The list below summarises the principal publicly-known Australian aerospace operators driving HVAC duct demand. The list is not exhaustive but covers the highest-density facility groupings.

Aerospace manufacturing

Boeing Aerostructures Australia (BAA) at Port Melbourne is the largest Australian aerospace component manufacturer, producing moveable trailing edge and flap assemblies for the Boeing 787 and the 777X. The site is a multi-bay manufacturing facility with composite layup, autoclave cure, machining and assembly. Marand Precision Engineering at Tullamarine produces weapons load adapter components and small-batch precision aerospace machining. Quickstep Holdings at Bankstown New South Wales is the largest Australian carbon fibre composite specialist with capability into the Boeing 787 and Airbus A380 supply chains. Cobham operates multiple sites at Brisbane and a number of regional aviation hubs. BAE Systems Australia operates at Williamtown (radar and electronic systems for the airborne fleet) and Henderson Western Australia (shipbuilding and related aerospace electronics). Northrop Grumman Australia operates at Adelaide, Sydney and Brisbane. Raytheon Australia is centred at Tewantin Queensland. Lockheed Martin Australia operates at Williamtown New South Wales (F-35 sustainment support) and Edinburgh South Australia. Saab Australia at Adelaide concentrates on radar and electronic warfare systems.

Commercial maintenance, repair and overhaul

Qantas Engineering is the largest Australian commercial MRO operator, with heavy-maintenance bases at Brisbane, Sydney Mascot, Avalon and Melbourne Tullamarine. The Qantas Brisbane facility is the principal wide-body heavy-maintenance base in Australia and is the dominant single-site HVAC demand node in the commercial MRO sector. Virgin Australia Maintenance is centred at Brisbane. Star Aviation MRO operates at Sydney and Melbourne. Hawker Pacific is the principal corporate aviation MRO at Sydney with secondary operations at Brisbane and Perth. Cobham operates multiple specialist MRO functions at Brisbane and elsewhere. Sikorsky Australia (Lockheed Martin-acquired) operates helicopter MRO at Sydney and Brisbane.

General aviation

Hawker Pacific is the Australian Cessna distributor and operates piston-aircraft and corporate-jet maintenance at Sydney, Brisbane and Perth. Cirrus Australia distributes the Cirrus SR-series single-engine piston aircraft. The Diamond Aircraft Australian distributor handles Diamond twin and single-engine piston aircraft. Robinson Helicopter Australia distributes the Robinson R22, R44 and R66 helicopters which dominate the Australian training and utility helicopter fleet. Bell Helicopter Australia (Babcock-owned) distributes the Bell commercial helicopter range.

Aeromedical and emergency services

The Royal Flying Doctor Service (RFDS) operates a national fleet of fixed-wing aeromedical aircraft from bases across every mainland state, with state divisions in Queensland, New South Wales, Victoria, South Australia, Western Australia and the Northern Territory. CareFlight, Westpac Lifesaver and the various state-based helicopter emergency medical services operate dedicated helicopter facilities concentrated in the major capital cities. Toll Aviation operates a mixed helicopter and fixed-wing fleet for medical and corporate transport.

Corporate aviation

BHP Air Operations and Rio Tinto Air Operations both maintain corporate fleets for fly-in fly-out mining operations, principally to the Pilbara from Perth. Network Aviation is the Qantas Group's regional and corporate operation, principally servicing Western Australian mining clients.

Defence sustainment within the aerospace industrial base

Boeing Defence Australia (BDA), Northrop Grumman Australia, Raytheon Australia, Lockheed Martin Australia, Sikorsky Australia (within Lockheed Martin) and Bell Australia (under Babcock) all contribute to the publicly-known defence sustainment portion of the Australian aerospace industrial base. The HVAC scope on the defence-aligned portion is covered in detail in our parallel defence and military HVAC duct guide — this article focuses on the commercial and component-manufacturing scope that sits in the same industrial precincts but operates under different procurement rules.

Aerospace research and industry bodies

CSIRO Aerospace Materials (within CSIRO Manufacturing) is the principal Australian aerospace materials research organisation. The Royal Aeronautical Society Australian Division coordinates the professional aerospace engineering community. The Australian Industry & Defence Network (AIDN), the Aerospace Industries Association Australia, and the Australian Helicopter Industry Association are the principal industry advocacy organisations and routinely host industry capability events that drive procurement-side decisions.

The standards stack — what aerospace HVAC is engineered against

Australian aerospace facility HVAC is designed against a layered stack of civilian Australian standards, NFPA documents adopted by reference, ATEX/IECEx hazardous-area standards, and the aerospace-specific quality management framework.

Australian civilian baseline

AS 1668.2 governs mechanical ventilation rates for general industrial and commercial buildings, and is the baseline for hangar, accommodation, office and amenity zones inside an aerospace facility. AS/NZS 4254 (parts 1 through 4) governs ductwork construction. AS 1530.4 covers fire resistance testing of building elements including duct penetrations and dampers. AS 3957 covers combustible dust handling in Australia and is the primary reference for the aluminium and titanium dust extract train. AS/NZS 60079 series governs hazardous-area equipment (Zone 0/1/2 for gas, Zone 20/21/22 for dust) and is applied throughout the jet fuel, LPG, aluminium dust, lithium battery and solvent storage zones. AS 1940 governs flammable and combustible liquids storage and handling, applied to paint mix rooms, solvent storage and the fuel system flush bay. AS 4114 specifically governs spray booth construction in Australia and is the primary aerospace paint booth reference. AS 1851 covers maintenance routines and is referenced in the operations-and-maintenance documentation for fire-rated dampers and smoke control. AS 1657 covers fixed platforms, walkways and ladders for access to elevated ducts and fans.

NFPA reference documents

NFPA 409 is the standard on aircraft hangars and the primary reference for hangar fire protection class, foam suppression compatibility, hangar door fire mode, and the mechanical ventilation rate during normal operation and fire response. NFPA 409 classifies hangars into Group I (large hangars, typically with high-volume low-expansion foam suppression), Group II (medium hangars, typically with low-level foam or AFFF suppression) and Group III (small hangars and general aviation, with sprinkler or sprinkler-plus-foam suppression). NFPA 410 covers aircraft maintenance ventilation including fuel-vapour management during routine maintenance activities. NFPA 415 governs airport terminal buildings, fuelling ramp drainage and aircraft fueling, and is the primary reference for any fuel handling area inside an aerospace facility envelope. NFPA 33 covers spray application using flammable or combustible materials and is the international reference behind AS 4114. NFPA 660 (the consolidated combustible dust standard, formerly NFPA 484 for combustible metals) is the primary reference for the aluminium-dust and titanium-dust extract train. NFPA 68 covers explosion venting and is the primary reference for the deflagration relief design on dust collectors and long horizontal extract duct runs.

Aerospace quality management

AS 9100 is the aerospace quality management system standard for organisations that design and manufacture products for the aviation, space and defence industry. AS 9110 is the parallel standard for aerospace maintenance, repair and overhaul (MRO) organisations — the certificated commercial MRO bases at Brisbane, Sydney, Avalon and Melbourne hold this. AS 9120 is the standard for aerospace distributors and stockists. Boeing Materials Quality Standards (BMQS) and Airbus AIS standards add a further procurement-side requirements on materials of construction, surface finishes and traceability.

Civil aviation regulation

CASR (the Civil Aviation Safety Regulations administered by CASA) sets the regulatory framework for Australian aviation maintenance organisations. CASR Part 145 covers approved maintenance organisations. CAR (the older Civil Aviation Regulations) remain in force for some legacy provisions. CAAPs (Civil Aviation Advisory Publications) provide guidance material. EASA Part 145 (European) and the FAA Repair Station Certificate under FAR Part 145 (United States) provide international cross-recognition. The HVAC scope is not itself a CASR Part 145 deliverable but the controlled environments fall within the certified facility scope.

Welding qualification and welded duct construction

AS 1796 and AS 2980 govern welder qualification for the personnel who fabricate welded stainless extract duct. AS 1554.1, AS 1554.6 and AS 1554.7 cover the welding of steel structures, stainless steel and special-purpose welding respectively. ISO 3834-2 governs the comprehensive quality requirements for fusion welding of metallic materials and is the aerospace-aligned welding QMS reference. Aerospace 316L stainless extract duct on the anodising, plating, paint booth and autoclave room paths is welded throughout — lockformed and crimped construction is not used because the seam path is a corrosion initiation point and a leakage path that the welded seam eliminates.

Safe Work Australia exposure standards

The Safe Work Australia Workplace Exposure Standards (WES) are the regulatory exposure limits that drive the design of the extract systems. The relevant entries for an aerospace facility are: aluminium dust respirable 1 mg/m³ and inhalable 10 mg/m³, with the combustible-dust deflagration risk governing before the inhalation risk; respirable crystalline silica 0.05 mg/m³ (applicable to composite mould preparation and grit-blast work); hexavalent chromium Cr(VI) 0.005 mg/m³ (anodising, chromate conversion, chrome plating); methyl ethyl ketone (MEK) 200 mg/m³; isopropyl alcohol (IPA) 400 mg/m³; acetone 500 mg/m³; toluene 50 mg/m³; xylene 50 mg/m³; naphtha 100 mg/m³; JP-8 jet fuel kerosene 100 mg/m³; polyurethane CARC isocyanate 0.005 ppm STEL (the killer — equal to the chrome plating WES in magnitude); composite dust (carbon fibre and epoxy) without formal WES but treated as irritant and cancer risk; respirable carbon fibre treated similarly; beryllium 0.002 mg/m³ (relevant to some legacy aerospace applications, extremely toxic); ozone 0.1 ppm (welding, laser cleaning, electrostatic finishing); MEK peroxide (composite curing — explosive in concentration). The duct system is sized to keep all of these below the WES in the worker breathing zone during the worst-case process activity, not the average.

Aircraft hangar HVAC — the commercial and general aviation scope

Aircraft hangars are the largest single mechanical-load buildings on most aviation sites, and the duct scope is correspondingly significant. The design approach varies by hangar class, by aircraft type and by the maintenance activity envelope.

NFPA 409 hangar classification

NFPA 409 classifies hangars by floor area, door height and the largest aircraft serviced. Group I hangars are large hangars exceeding 12,000 sq ft (approximately 1,115 m²) with door heights typically exceeding 8.5 m, used for wide-body commercial aircraft and military transports. Suppression is high-volume low-expansion foam (Aqueous Film Forming Foam, AFFF) discharged from overhead monitors and through floor pop-up nozzles. The mechanical ventilation rate during normal operation is typically 6-10 air changes per hour, with surge capacity to 15 ACH during fuel system flush, engine ground run or paint touch-up. The HVAC fire mode is interlocked with the foam discharge — the supply fans shut down, the extract continues at reduced rate to remove smoke and combustion products, and the hangar door closes to maintain the suppression envelope.

Group II hangars are medium hangars up to 40,000 sq ft (3,716 m²) typically used for medium commercial aircraft and large business jets. Suppression is typically AFFF at a lower discharge rate than Group I. Ventilation rates and fire-mode logic are similar in structure to Group I but at smaller scale. Group III hangars are small hangars up to 12,000 sq ft typically used for small commercial aircraft, helicopters and general aviation. Suppression is typically sprinkler or sprinkler-plus-foam. The general aviation hangars at Bankstown, Moorabbin, Archerfield, Jandakot and Parafield are predominantly Group III, with a small number of Group II facilities for the larger corporate jet operators.

Cathedral-bay geometry and air distribution

Wide-body commercial MRO hangars typically run to a clear interior height of 18-25 m to accommodate a Boeing 747, A380 or 777 on jacks with overhead crane access. The Qantas Brisbane heavy maintenance hangar accommodates wide-body aircraft on multiple parallel lanes. The supply air strategy is typically displacement ventilation with high-volume low-velocity diffusers at low level or at intermediate height, because conventional ceiling-supply throws disturb pre-flight ground-runs, wash hydraulic-fluid mist back onto the aircraft and create localised condensation on cold airframe surfaces during winter operations. Duct routing follows the roof truss zone with vertical drop legs to the lower-level diffusers. Duct lengths in a single wide-body hangar typically run to 1,200-2,500 m of fabricated sheet across supply, return and exhaust paths.

Heat extract over engine ground-test areas

Engine ground-test is a common activity in commercial MRO and helicopter overhaul facilities. The aircraft is restrained on a test stand or on its own brakes, the engines are run at idle through to high power, and the exhaust temperature at the duct intake reaches 300-500 degrees C during test. The heat extract is a dedicated path with 316L stainless duct rated for the elevated temperature, refractory lining at the hottest section near the engine exhaust, and a separate fire compartment for the test area. The duct material on the cooler downstream section drops to 304L stainless or aluminised steel once the temperature falls below 200 degrees C, then to standard hot-dip galvanised once the temperature falls below 100 degrees C. The extract stack discharge follows AS 1668.2 plume rise requirements and is sized to avoid recirculation into the supply intake.

Hangar door air seal in fire mode

The hangar door is the single largest opening in the building envelope and is the most challenging air-seal problem on the project. In normal operation the door is open during aircraft movement and closed during maintenance work. In fire mode the door has to close and seal against the foam suppression overpressure and the smoke-control envelope. The door interlock with HVAC fire mode is critical — the door closure sequence has to lead the HVAC fire-mode response by 10-15 seconds to avoid drawing combustion products back into the building. The seal class is set by the foam suppression overpressure requirement (typically 50-100 Pa above ambient during discharge) and by the smoke-control fan capacity per NFPA 92 or AS 1668.1.

Foam fire suppression compatibility

The HVAC system is part of the foam fire suppression envelope and has to be compatible with the foam discharge. During discharge, the supply fans shut down to avoid blowing foam off the protected surfaces. The extract continues at a reduced rate to remove smoke and combustion products without disrupting the foam blanket. The duct material in the foam-discharge zone is selected to resist the wet foam residue post-event — typically 316L stainless on the lower-level return and any extract paths within 2-3 m of the floor, with hot-dip galvanised acceptable at higher elevations that the foam blanket does not reach. The HVAC controls system has a documented post-foam-discharge recovery sequence that includes wash-down of duct surfaces, replacement of any contaminated air filters and re-commissioning of the supply fans.

Composite manufacturing HVAC — the aerospace cleanroom scope

Aerospace composite manufacturing combines the cleanroom discipline of pharmaceutical manufacturing with the chemistry discipline of paint shops and the thermal management of small-scale process autoclaves. The HVAC duct scope per square metre of facility is the highest of any aerospace facility category. The principles overlap with the civilian composite manufacturing scope covered in our composite manufacturing HVAC duct guide but with aerospace-specific overlays on cleanroom class, materials traceability and audit evidence.

Composite layup cleanroom

Carbon fibre prepreg layup is performed in an ISO 7 (Class 10,000 by the older Federal Standard 209E nomenclature) cleanroom. The supply air is HEPA H13 filtered through ceiling-mounted terminal filters with downflow at 0.20-0.30 m/s at the working face. The return air is low-level perimeter through grilles in the wall base. Temperature is controlled to 20-22 degrees C with stability of plus-or-minus 1 degree C across the cleanroom volume. Relative humidity is controlled to 30-55 per cent depending on the resin system — the lower end for epoxy systems that absorb moisture, the higher end for systems that benefit from controlled humidity for resin viscosity stability. ESD protection is provided through static-dissipative flooring, grounded work surfaces and operator personnel grounding.

The duct construction is 316L stainless steel throughout the cleanroom supply and return paths. Lockformed and crimped galvanised construction is not acceptable because the seam path is a particulate-shedding source over time and the galvanic-incompatibility with the carbon fibre lay-up creates a corrosion concern at material interfaces. The longitudinal duct seam is welded using the SB-ZF1500 automatic stitchwelder to produce a crevice-free seam, and the transverse joints use TDF flanges with stainless gaskets. Internal surfaces are pickle-passivated to remove the heat-affected zone discolouration from welding and to establish the corrosion-resistant chromium oxide layer.

Autoclave cure room

Composite autoclaves cure prepreg components under combined pressure and temperature. Typical aerospace epoxy cure cycles run at 180-220 degrees C and 7-14 bar of nitrogen pressure for 7-14 hours per cycle. The autoclave is a pressure vessel installed inside a vault that has to manage four hazards simultaneously: heat rejection from the autoclave shell during cure, nitrogen displacement of breathable air during normal autoclave operation (nitrogen is the pressurising medium, not breathable air), possible epoxy off-gassing in a failed-cure scenario, and the explosion-relief venting required if a curing run goes outside envelope.

The autoclave room is designed as a separate AS 1668.2 mechanical ventilation zone with 6-10 air changes per hour, oxygen depletion monitoring (target 19.5 per cent O2 minimum at breathing height with audible alarm at 19.0 per cent and operations halt at 18.5 per cent), heat extract from the autoclave shell area with capacity to remove 50-100 kW thermal load during the cure cycle, and an emergency nitrogen-purge fan capable of clearing the room volume in under 5 minutes. The duct material is 316L stainless because hot epoxy off-gassing creates a corrosive mist in any failed-cure event, and the autoclave shell radiates heat that the duct system has to manage without becoming an ignition source for any released nitrogen-air mixture above the lower explosion limit of the off-gas chemistry.

Composite trim-and-drill bay

Post-cure trim-and-drill operations on cured composite parts generate respirable carbon fibre dust, epoxy dust and abrasive dust from the cutting and grinding tools. The extract is sized for face velocity at every drill, router, trim saw and grinding station — typically 0.5-1.0 m/s at the open face for a downdraft table and 25-30 m/s in the duct cross-section for adequate particulate transport. The duct material is 316L stainless throughout, with a HEPA H13 final filter stage upstream of the extract fan to capture the respirable fraction. Carbon fibre has no formal Safe Work Australia WES but is recognised as an irritant and a cancer risk — local exhaust ventilation with HEPA filtration is the engineering control of record, supplemented by personal respiratory protection at the operator station.

Bond room

Secondary bonding operations attach pre-cured composite components, metallic fittings and substructure brackets using structural adhesives. The adhesive chemistries include epoxy, polyurethane and methacrylate systems, with mixing performed inside the bond room and applied to the work surface. The bond room is a separate AS 1668.2 zone with HEPA H13 supply at lower volume than the layup cleanroom (the bond room does not need to be ISO 7 in most aerospace applications, but it does need controlled-particulate supply to maintain the bond surface preparation). Adhesive fume extract is provided at every bonding station with 316L stainless duct and a charcoal stage upstream of the discharge.

Aluminium dust, titanium dust and combustible dust HVAC

Aerospace component manufacturing concentrates more combustible-dust mass per square metre than almost any other manufacturing category. Aircraft alloys 7075 (Al-Zn-Mg-Cu), 2024 (Al-Cu-Mg) and 2014 (Al-Cu-Mg-Si) all generate aluminium dust when machined, drilled, sanded, polished, sawn or ground. Titanium is in the same category. The deflagration index Kst of the dust mixture exceeds 200 bar·m/s in most aerospace alloy applications, placing the dust in dust hazard class St3 — the highest combustibility class in the international classification system.

NFPA 660 and AS 3957 framework

NFPA 660 (the consolidated combustible dust standard, formerly NFPA 484 for combustible metals) is the international primary reference for the aluminium-dust and titanium-dust extract train. AS 3957 is the Australian standard governing combustible dust handling. The combination drives a multi-layered engineering response that has to address ignition control, propagation control, deflagration relief, and operator protection.

Spark-resistant fans

Every fan in the combustible-dust extract train is rated spark-resistant per AMCA classification. Class A (no aluminium parts in contact with rotating components), Class B (non-ferrous wear plates at potential rubbing surfaces) or Class C (full non-ferrous construction including impeller) is selected based on the dust deflagration risk and the layout of the system. No carbon-steel impellers are permitted in the dust train because the steel-on-aluminium rubbing contact during fan startup or trip is a documented ignition source. The fan motor is positioned outside the airstream where possible, with a TEFC enclosure and an external cooling fan.

Continuous metal duct with bonded-static path

The extract duct is continuous metal (typically 316L stainless or hot-dip galvanised on the dust-side, with 316L preferred for the moist coolant-mist load that often accompanies aluminium machining) with no flexible duct in the combustible-dust extract train. The duct is electrically bonded throughout to avoid static charge accumulation, with a documented continuity test as part of the commissioning record. Internal duct linings are prohibited because they harbour dust accumulation that becomes a secondary deflagration source.

NFPA 68 explosion venting

NFPA 68 explosion venting is provided on dust collectors and on long horizontal duct runs that could otherwise sustain a deflagration pressure rise. The vent is sized against the Kst of the dust and the volume protected, with venting to a safe location outside the building envelope. The vent panel construction is rupture-disc style at calibrated burst pressure, and the vent dump zone is engineered to exclude personnel and ignition sources.

Wet dust collection

Where the dust inventory exceeds the AS 3957 and NFPA 660 threshold quantity for dry collection, the dust collector is a wet type rather than a dry filter cartridge collector. Wet collection submerges the dust in water inside the collector vessel, suppressing both the deflagration risk and the secondary dust release at filter change-out. The wet collector discharges to a settling tank and then to a hazardous waste path. The duct material immediately upstream of the wet collector is 316L stainless because the moist back-flow from the collector vessel attacks galvanised construction.

Spark detection and suppression

Modern aerospace dust extract systems include infrared spark detection in the duct cross-section with a fast-acting water spray or inert gas injection upstream of the dust collector. The spark detection and suppression system reduces the deflagration risk further by extinguishing ignition sources before they reach the collector vessel. The system is interlocked with the extract fan trip and the suppression discharge to provide a coordinated response.

Anodising, chromate conversion and plating — the hexavalent chromium scope

Aerospace surface treatment of aluminium alloys uses chromate-sulphuric acid anodising, chromate conversion coating (also called Alodine or Iridite) and selective chrome, nickel, cadmium and copper plating. All of these processes release hexavalent chromium Cr(VI) mist into the extract air stream. The Safe Work Australia WES for Cr(VI) is 0.005 mg/m³ — one of the lowest exposure limits in the WES schedule, on a par with cyanide and inorganic arsenic.

Push-pull lip extract

Every anodising, chromate conversion and plating tank carries push-pull lip extract. The push air jet enters from one side of the tank lip at controlled velocity, sweeping the rising vapour and mist across the tank surface to the extract slot on the opposite side. The slot velocity and the push-pull balance are set to capture the rising plume without disturbing the tank surface chemistry. The capture face is sized for the tank dimensions and the worst-case process condition (typically the hot rinse or the initial immersion).

316L stainless welded ductwork

The duct material on the anodising and chromate conversion line extract is 316L stainless steel throughout, with welded crevice-free seams produced by the SB-ZF1500 automatic stitchwelder. Lockformed galvanised construction is unsuitable because Cr(VI) mist attacks zinc within months and creates a downstream corrosion path. The internal duct surface is pickle-passivated after fabrication to establish the chromium oxide passive layer.

Wet packed-bed scrubber

The extract discharge passes through a wet packed-bed scrubber before atmospheric release. The scrubber uses a counter-current water spray over a packed media bed to capture the Cr(VI) mist and the sulphuric acid mist, with neutralisation chemistry added to the recirculating sump water to maintain pH and to convert dissolved Cr(VI) to less-hazardous Cr(III) before disposal. The scrubber discharge fan is 316L stainless construction throughout, with a mist eliminator upstream and the stack outlet sized for plume rise to avoid downwash on the building.

Chrome, nickel, cadmium and copper plating

Selective chrome plating, nickel plating, cadmium plating and copper plating release a mixed metal-acid mist with the same engineering response as anodising. Cadmium adds the additional concern that cadmium WES is 0.001 mg/m³ inhalable and cadmium is a recognised human carcinogen — the engineering control is the same as for Cr(VI) but with more stringent monitoring. Chrome plating tanks evolve hydrogen at the cathode and require Zone 1 ATEX/IECEx classification per AS/NZS 60079 on the immediate tank surround.

Paint booth HVAC — AS 4114 isocyanate scope

Aircraft livery painting uses isocyanate polyurethane hardener chemistry. The colours are well known — Boeing white, Airbus blue, Qantas red-tail livery, Virgin Australia red, and the various regional fleet finishes. The chemistry is the same across all of them, and the isocyanate hardener is among the most dangerous airborne chemistries on any industrial site. The Safe Work Australia STEL for polyurethane isocyanate is 0.005 ppm — equal in magnitude to the chrome plating Cr(VI) WES and one of the lowest exposure limits in the WES schedule.

AS 4114 downdraft booth design

AS 4114 governs spray booth construction in Australia, with NFPA 33 as the international reference. The aerospace paint booth is a downdraft design — supply air enters at the ceiling at low velocity through a perforated plenum, and extract air leaves through a grating in the floor. The face velocity at the operator is 0.5 m/s minimum, with 0.4-0.6 m/s as the typical design target. The booth dimensions are sized to the largest aircraft serviced — a wide-body MRO paint hangar at Qantas Brisbane or a comparable facility is 80-100 m long, 50-70 m wide, with internal clear height of 20-25 m. A general aviation paint booth at a smaller facility might be 12-15 m long, 8-10 m wide, with internal clear height of 5-6 m.

Three-stage extract filtration

The extract air passes through three filtration stages before atmospheric discharge. The first stage is a paint-arrestor filter sized to capture the bulk overspray and prevent the downstream stages from clogging. The second stage is activated carbon for the volatile organic compound (VOC) and isocyanate gas-phase capture. The third stage is HEPA H13 for the fine particulate residue and any micro-encapsulated isocyanate aerosol that escapes the carbon stage. The stages are housed in a dedicated filter house adjacent to the booth, with bag-in/bag-out access for safe replacement under contamination.

316L stainless extract duct

The extract duct is 316L stainless steel throughout, with welded crevice-free seams. The isocyanate condensate that accumulates in the duct attacks galvanised steel and creates a downstream contamination path that is impossible to clean. The duct is sloped to a low-point sump with a drain trap on the recirculating wash water, and the duct is rinsed at planned intervals to remove accumulated condensate. The duct internal surface is electropolished where the contamination management plan calls for the highest cleanability standard.

Operator-supplied air respirator

The paint booth HVAC system protects the surrounding facility, not the painter. The painter wears a supplied-air respirator with breathing air drawn from a separate compressor and filtered through a dedicated dryer-coalescer-charcoal cartridge train. The supplied-air system is a separate HVAC scope from the booth itself but is typically supplied by the same mechanical contractor and is commissioned at the same time.

Paint mix room and solvent storage

The paint mix room and solvent storage area falls under AS 1940 (flammable and combustible liquids) with Zone 2 IECEx classification per AS/NZS 60079 on the immediate solvent storage envelope. The mechanical ventilation rate is 12 air changes per hour minimum during occupied operation, with surge to higher rates during mixing operations. Electrical fittings inside the zone are intrinsically safe or explosion-proof rated, and the leak detection is interlocked to an emergency stop on the mixing equipment.

Engine test cell and engine MRO HVAC

Engine test cells are the most thermally extreme HVAC zones in a commercial MRO facility. The aircraft engine is restrained on a test stand, run from idle through to maximum power for performance verification after overhaul, and the exhaust temperature at the duct intake reaches 400-600 degrees C during peak test runs.

High-temperature exhaust stack

The exhaust path is a dedicated 316L stainless duct with refractory lining at the hottest section near the engine exhaust. The duct cross-section is sized for the engine maximum exhaust mass flow plus an entrainment ratio that mixes ambient cooling air into the exhaust to reduce the temperature at the stack outlet. Typical entrainment ratios are 3:1 to 6:1 (cooling air to exhaust gas) to bring the stack outlet temperature below 200 degrees C. The stack discharge follows AS 1668.2 plume rise requirements and is sized to avoid recirculation into any supply intake on the same building or any adjacent building.

Intake silencing

The test cell intake provides the air mass flow that the engine consumes during the test run. For a large commercial turbofan engine the intake mass flow can exceed 400 kg/s at maximum power. The intake silencer is sized for the acoustic attenuation required to maintain external noise compliance, with multiple parallel splitter modules and a labyrinth path that absorbs the low-frequency engine noise.

Acoustic isolation

The test cell is a dedicated fire compartment with substantial acoustic isolation. The wall construction is layered concrete plus mineral wool plus inner acoustic panel, with the duct penetrations through the acoustic envelope detailed as low-leakage labyrinth seals. The HVAC duct system is decoupled from the wall structure with flexible connectors at the boundary, and the cooling-air paths are routed to avoid creating noise leakage paths through the building envelope.

Engine teardown and overhaul

The engine teardown and overhaul bay is a separate facility from the test cell. The teardown bay handles inspection, parts cleaning, repair and reassembly of the engine. The HVAC scope is dominated by cleaning solvent extract (MEK, IPA, naphtha — all with WES discussed above), parts wash bay extract, hot-section inspection booth (X-ray and dye penetrant) and the controlled-environment reassembly room which requires ISO 8 cleanroom class or better for the bearing and seal assembly operations.

Avionics integration and ESD-controlled zones

Avionics integration covers the installation, testing and certification of radar, identification friend-or-foe (IFF), datalink, flight management systems, autopilot computers and the various electronic systems that constitute the aircraft's nervous system. The HVAC scope for these zones is a controlled-environment cleanroom with ESD protection and tight thermal stability.

Controlled environment

The avionics integration zone is typically controlled to 20-22 degrees C with stability of plus-or-minus 1 degree C, 40-50 per cent relative humidity, MERV 14 supply filtration and redundant N+1 cooling. The supply air is a positive overpressure cascade from outer zones inward, with HEPA H13 at the final stage if the avionics work involves any clean-room class. ESD protection is provided through static-dissipative flooring, grounded work surfaces and operator personnel grounding, and the supply air ionisation is controlled to avoid creating ESD events on the assembly bench.

Climate-controlled environmental test chamber

The climate test chamber is used for component-level environmental qualification under temperature extremes. Typical chambers run from -55 degrees C to +85 degrees C in a controlled ramp, with humidity control across the upper portion of the temperature range. The HVAC scope for the chamber itself is the refrigeration plant rather than the ductwork, but the surrounding test laboratory carries a substantial HVAC duct scope for the chamber heat rejection and the operator gallery ventilation.

Environmental stress screening (ESS)

ESS combines vibration, thermal cycling and altitude simulation to expose component defects during qualification testing. The ESS chamber is a smaller volume than the climate chamber but with more aggressive thermal cycling rates. The HVAC scope is similar in structure to the climate chamber — refrigeration plant for the chamber itself and operator gallery ventilation for the surrounding laboratory.

Fuel system, oxygen system and battery shop HVAC

The fuel system, oxygen system, hydraulic system and battery shop areas concentrate hazardous-area HVAC scope into a small fraction of the facility footprint. Each carries a distinct zone classification and engineering response.

JP-8 jet fuel system flush and test

Aircraft fuel system flush, drain, refill and integrity test is performed at scheduled intervals during heavy maintenance. The bay is classified Zone 1 under AS/NZS 60079 for the gas-air mixture risk during fuel handling. The Safe Work Australia WES for JP-8 jet fuel kerosene is 100 mg/m³ — relatively high compared to the heavy metals discussed above, but the deflagration risk governs the engineering design before the inhalation risk does. The extract duct is 316L stainless throughout, with hydrocarbon leak detection on the duct cross-section and intrinsically safe instrumentation. Emergency stop interlock with the building gas detection system provides the rapid shutdown response.

Oxygen system filling

Aircraft crew oxygen system filling uses pure oxygen or oxygen-enriched air, depending on the aircraft type. The bay is a dedicated fire compartment with substantial separation from the surrounding facility — pure oxygen is not a fuel in itself but it accelerates combustion of any fuel that is present, and the engineering response treats every surface inside the oxygen filling bay as a potential ignition initiator. The HVAC scope is light-duty in terms of duct quantity but high in specification — 316L stainless throughout, oxygen-clean preparation of internal surfaces, and dedicated personnel decontamination on entry.

Hydraulic system fill and bleed

Aircraft hydraulic systems use Skydrol (phosphate ester) or Aeroshell (mineral-based) hydraulic fluid depending on the aircraft type. Both fluids are mildly toxic on skin contact and produce vapour during fill, bleed and test operations. The bay is classified Zone 2 under AS/NZS 60079 for the vapour risk, with mechanical extract at 12 air changes per hour minimum during occupied operation and surge to higher rates during fill or bleed events. Skydrol attacks paint and many gasket materials — the duct material is 316L stainless and the gasket selection is fluorocarbon (Viton) or equivalent.

Battery shop — lead-acid and lithium-ion

Aircraft batteries include lead-acid for legacy aircraft fleets (the older general aviation fleet and some helicopter applications) and lithium-ion for modern commercial aircraft (the Boeing 787 main battery being the prominent example). Lead-acid battery shops require AS/NZS 60079 Zone 2 hydrogen ventilation, with mechanical extract sized to keep hydrogen concentration below 1 per cent of the lower explosion limit (4 per cent hydrogen by volume in air). Lithium-ion battery storage and servicing fall under NFPA 855 with dedicated thermal-runaway extract, smoke detection compatible with FM-200 or water-mist suppression, and segregated storage cells with passive ventilation to separate any single-cell thermal event from the broader storage area.

Tyre and wheel shop

The tyre and wheel shop services aircraft tyres (Bridgestone, Michelin, Goodyear are the principal brands) and wheel assemblies. The HVAC scope is light-duty — general industrial ventilation at AS 1668.2 rates for the bay, dust extract at the tyre tread machining operation, and parts wash bay extract for the wheel bearing service work.

NDT laboratory and inspection HVAC

The non-destructive testing (NDT) laboratory performs X-ray, ultrasonic, dye penetrant and eddy current inspection of aircraft components. The HVAC scope is small in floor area but specific in engineering response.

X-ray inspection room

The X-ray inspection room is a shielded enclosure with concrete or steel-and-lead wall construction. The HVAC scope includes general ventilation at AS 1668.2 rates and a low-volume extract on the chemical processing area for the X-ray film development chemistry (the older silver halide film process is still used in some Australian aerospace applications, with the digital direct radiography process replacing it in newer facilities). The duct material on the chemical processing extract is 316L stainless because the developer and fixer chemistry attacks galvanised construction.

Ultrasonic inspection

Ultrasonic inspection uses water or coupling gel as the ultrasonic transmission medium between the transducer and the part. The HVAC scope is minor — general ventilation only.

Dye penetrant and magnetic particle inspection

Dye penetrant inspection uses fluorescent or visible dye penetrant chemistry, with developer powder to draw the dye out of any surface defect. Magnetic particle inspection uses iron oxide powder and an applied magnetic field. Both processes generate a chemical mist that requires extract at the inspection bench. The duct material is 316L stainless for the dye penetrant line and standard galvanised for the magnetic particle line.

Eddy current inspection

Eddy current inspection is performed at the part with a hand-held probe. The HVAC scope is minor — general ventilation only.

Material selection by aerospace facility zone

Material selection on aerospace projects is driven by chemistry, by combustion risk and by lifecycle. The default material set we apply across SBKJ-supplied aerospace projects is summarised below.

316L stainless steel

316L stainless steel (low-carbon variant for weld-zone corrosion resistance) is the default for all aerospace process extract paths. The applications include: chromate-sulphuric anodising line extract, chromate conversion coating line extract, chrome plating, nickel plating, cadmium plating, copper plating, paint booth extract, paint mix room solvent extract, autoclave cure room extract, composite layup cleanroom supply and return, composite trim-and-drill HEPA extract, bond room adhesive extract, JP-8 jet fuel system flush extract, hydraulic system fill and bleed extract, oxygen system filling, engine test cell high-temperature exhaust (downstream of the refractory-lined section), and the wet packed-bed scrubber duct on every chemical extract train.

The surface finish is 2B as standard with a 2B-DD or BA upgrade for visible architectural duct. Internal pickle-passivation after fabrication establishes the corrosion-resistant chromium oxide passive layer and is a contracted deliverable on every aerospace extract scope.

304L stainless steel

304L stainless is used as a cost-down substitute for 316L on extract paths where the chloride exposure and the acid mist loading are demonstrably low. Typical applications include some kitchen exhaust on canteen amenity, dye penetrant inspection bench extract (where the developer powder is benign), and some general laboratory exhaust. It is not used on Cr(VI) extract, on isocyanate extract or on jet fuel extract regardless of cost-down pressure.

Hot-dip galvanised G275 carbon steel

Hot-dip galvanised G275 (275 g/m² zinc coating to AS 1397) is the workhorse for the non-aerospace portion of the facility — accommodation, offices, canteen, gymnasium, medical centre, training rooms and the general circulation HVAC. It is also acceptable on the cooler downstream sections of the engine test cell exhaust (once the temperature falls below 100 degrees C) and on the upper-level hangar ventilation that sits above the foam-suppression discharge envelope.

Aluminium and aluminium-zinc

Aluminium ducts are not generally used in aerospace facilities because aluminium burns once the surface oxide layer is breached — the same property that makes the aerospace alloy dust combustible applies to a duct made from the same alloy. The Aluzinc AZ150 (aluminium-zinc 150 g/m² coating) duct is used in specific cases where galvanic compatibility with aluminium structure is required, but the application is narrow.

Pre-insulated phenolic and PIR duct

Pre-insulated phenolic and polyisocyanurate panel duct is used in some accommodation and amenity applications where space and weight constraints govern. It is not used in aerospace process zones because the foam core cannot meet the cleanroom particulate-shedding requirement and is not compatible with the Cr(VI) and isocyanate chemistry on the extract side.

Worker amenity and accommodation HVAC

The bulk of the duct quantity by linear metre on a major aerospace facility is in worker amenity and accommodation systems, which follow commercial Australian standards with aerospace overlays for FOD control and access management.

Canteen and worker amenity

Canteen and worker amenity HVAC follows commercial recreational and food service standards. The duct construction is standard hot-dip galvanised G275 sheet with TDF flanges, sized to AS 1668.2 Table 3.3 rates. Kitchen exhaust on canteens follows the same rules as commercial kitchen exhaust — typically 1.2 mm minimum gauge, fully welded construction in the cooking zone, with cleanout access at every change of direction. The amenity HVAC sits on a separate plant from the aerospace process HVAC and is not shared with the controlled-environment zones.

Office and engineering

Engineering office and IT HVAC follows commercial office standards with overlays for IT redundant cooling. The duct construction is standard hot-dip galvanised sheet with TDF flanges, with VAV terminal boxes at each zone for occupancy-controlled ventilation. The IT room is typically a small data centre class with N+1 redundant cooling and tight thermal envelope per ASHRAE TC 9.9.

Security gatehouse

The security gatehouse at the facility perimeter operates 24/7 and requires redundant cooling. The HVAC scope is small in duct quantity — the gatehouse is typically 50-100 m² of conditioned space — but high in availability requirement.

Tooling crib and spares

The tooling crib and aerospace spares storage operates as a controlled-access store with environmental conditioning to preserve the precision tooling and the long-shelf-life spares. The HVAC scope is small in duct quantity but specific in humidity control — typically 20-22 degrees C and 30-45 per cent RH year-round.

Boeing Aerostructures Australia, Quickstep and Marand — component manufacturer profiles

The three principal Australian aerospace component manufacturers each carry a distinct HVAC duct scope profile based on the product mix and the process portfolio.

Boeing Aerostructures Australia, Port Melbourne

Boeing Aerostructures Australia at Port Melbourne is the largest Australian aerospace component manufacturer. The site produces moveable trailing edge and flap assemblies for the Boeing 787 Dreamliner and is contracted for the upcoming 777X production. The HVAC scope spans composite layup cleanrooms, autoclave cure rooms, 5-axis CNC machining bays for titanium and aluminium parts, aluminium sheet metal fabrication for skin panels, riveting and bonding cells, post-cure trim-and-drill stations, paint booth (protective and primer coatings, with the final livery applied downstream at the airline), engine integration mock-up and inspection laboratory. The facility footprint is 50,000-80,000 m² with substantial expansion through the 777X programme.

The duct material mix is heavily skewed to 316L stainless on the extract side — the anodising line, the chromate conversion line, the paint booth extract, the autoclave room extract, the composite cleanroom HEPA supply and return, the bond room extract, and the trim-and-drill HEPA extract all carry 316L specification. The hot-dip galvanised G275 portion of the scope serves the accommodation, office, canteen and general circulation paths.

Quickstep Holdings, Bankstown NSW

Quickstep Holdings at Bankstown New South Wales is the principal Australian aerospace composite specialist. The site manufactures carbon fibre composite components for the Boeing 787, Airbus A380 panels and a number of other commercial and defence programmes. The HVAC scope is dominated by the composite layup cleanroom (ISO 7 with HEPA supply, ESD protection, controlled temperature and humidity), the autoclave cure room (separate zone, 180-220 degrees C, 7-14 bar nitrogen, oxygen depletion monitoring), the prepreg storage and freezer area (controlled below 0 degrees C to preserve the prepreg shelf life), the post-cure trim-and-drill bay with HEPA dust extract, the bond room for secondary bonding operations with adhesive fume extract, and the NDT laboratory for X-ray, ultrasonic and dye penetrant inspection.

The duct quantity per square metre of facility is the highest of any aerospace facility category because the cleanroom and the controlled chemistry zones impose tighter ventilation rates than a general manufacturing shop.

Marand Precision Engineering, Tullamarine VIC

Marand Precision Engineering at Tullamarine Victoria represents a different profile — precision aerospace machining for weapons load adapter components and other small-batch structural parts. The HVAC scope is dominated by the 5-axis CNC machining bay with coolant mist extract, the materials handling chemistry (cutting fluid storage, inspection chemistries) and the inspection and dimensional metrology room which requires tight thermal stability. The duct quantity per square metre is lower than the composite specialist but the chemistry mix is distinct — cutting fluid mist and titanium chip handling dominate the extract scope.

Qantas Engineering and the commercial MRO scope

Qantas Engineering is the largest Australian commercial MRO operator and the dominant single-site HVAC demand node in the commercial sector. The Brisbane heavy maintenance base accommodates wide-body aircraft on multiple parallel lanes with a facility footprint exceeding 40,000 m². The Sydney Mascot, Melbourne Tullamarine and Avalon bases provide additional capacity at different scales.

Wide-body heavy maintenance hangar

The wide-body heavy maintenance hangar is the dominant HVAC scope. The hangar volume is 200,000-400,000 m³, with NFPA 409 Group I or Group II classification depending on the specific facility. The mechanical ventilation rate during normal operation is 6-10 air changes per hour, with surge capacity to 15 ACH during fuel system flush, engine ground run or paint touch-up. The supply air strategy is displacement ventilation with low-level diffusers and ceiling extract. The duct quantity in a single wide-body hangar runs to 5,000-8,000 m² of fabricated sheet.

Paint shop

The Qantas Brisbane paint shop and the equivalent facilities at other commercial MRO bases handle full aircraft livery work on wide-body, narrow-body and regional aircraft. The booth is a downdraft design to AS 4114 with face velocity at the operator of 0.5 m/s minimum. The extract is three-stage filtered (paint arrestor, activated carbon, HEPA H13) with 316L stainless duct throughout. The booth dimensions are sized for the largest aircraft serviced.

Engine teardown and overhaul

Commercial engine teardown and overhaul covers the major commercial engine families. The bay handles inspection, parts cleaning, repair and reassembly. The HVAC scope covers cleaning solvent extract, parts wash bay extract, hot-section inspection booth (X-ray and dye penetrant) and the controlled-environment reassembly room. The duct material mix is 316L stainless on the chemistry-bearing extract paths and hot-dip galvanised on the general ventilation.

Fuel system flush and test bay

The fuel system flush and test bay handles aircraft fuel system maintenance with JP-8 kerosene. The bay is Zone 1 ATEX/IECEx with 316L stainless extract duct, hydrocarbon leak detection and emergency stop interlock.

Avionics integration

The avionics integration zone is a controlled-environment cleanroom for the installation, testing and certification of aircraft electronic systems. The HVAC scope is small in floor area but specific in environmental control — 20-22 degrees C, 40-50 per cent RH, MERV 14 filtration, redundant N+1 cooling.

Accommodation, office, canteen and amenity

The accommodation, office, canteen and amenity HVAC follows commercial Australian standards on hot-dip galvanised G275 ductwork. The scope is the largest single duct quantity on the project by linear metre.

General aviation and helicopter overhaul HVAC profile

The general aviation hangar and the helicopter overhaul facility carry a substantially smaller HVAC duct scope than the commercial MRO or the component manufacturer, but a single Australian aerospace contractor portfolio typically includes 5-10 of these smaller facilities at any time.

Bankstown, Moorabbin, Archerfield, Jandakot, Parafield

The principal Australian general aviation airports host a substantial concentration of small piston-aircraft maintenance facilities, light helicopter operators, corporate jet bases and flight training schools. The HVAC scope at each individual facility is 200-500 m² of fabricated sheet duct, but the cumulative scope across all five airports runs to several thousand square metres of fabricated sheet duct per year in routine maintenance and upgrade work.

Hawker Pacific and Cirrus Australia

Hawker Pacific operates the Australian Cessna distribution and piston-aircraft maintenance at Sydney, with secondary operations at Brisbane and Perth. Cirrus Australia distributes the Cirrus SR-series single-engine piston aircraft. The HVAC scope at these facilities is typical general aviation hangar profile with light maintenance bay extract and small-volume amenity.

Robinson Helicopter Australia and Bell Australia

Robinson Helicopter Australia distributes the Robinson R22, R44 and R66 helicopters which dominate the Australian training and utility helicopter fleet. Bell Helicopter Australia (Babcock-owned) distributes the Bell commercial helicopter range. The helicopter HVAC scope is hangar-driven with gearbox lubricant extract, hydraulic system bleed, rotor blade dynamic balancing and engine teardown overlay.

RFDS and aeromedical helicopter fleets

The Royal Flying Doctor Service operates a national fleet of fixed-wing aeromedical aircraft from bases across every mainland state. CareFlight, Westpac Lifesaver and the various state-based helicopter emergency medical services operate dedicated helicopter facilities concentrated in the major capital cities. The HVAC scope at each base includes hangar ventilation, medical equipment storage with controlled humidity, the aeromedical fit-out workshop and the operations centre. The duct material mix is dominated by hot-dip galvanised G275 with 316L stainless on any oxygen system filling or hydraulic system bleed extract.

BHP Air, Rio Tinto Air, Toll Aviation, Network Aviation

The corporate aviation fleets servicing mining and corporate transport carry a hangar-driven HVAC profile similar to general aviation but at slightly larger scale, with paint touch-up and minor structural repair capability at the larger bases. The duct quantity per facility is 800-2,000 m² of fabricated sheet.

SBKJ machinery selection for aerospace HVAC fabrication

SBKJ Group's machine portfolio supports the sheet-metal portion of aerospace HVAC ductwork — the supply, return and extract duct fabrication that constitutes 90 per cent of the project scope by linear metre. The recommended machine set differs between the aerospace process zones (316L stainless, welded extract) and the accommodation and amenity zones (hot-dip galvanised, lockformed TDF construction).

SBAL-V auto duct line — stainless variant for aerospace process extract

The SBAL-V Auto Duct Line in 316L stainless variant is the principal machine for aerospace process extract ducts — the anodising line, the chromate conversion line, the chrome plating, the paint booth extract, the autoclave room extract, the composite layup cleanroom, the bond room and the engine test cell downstream section. The machine handles material thickness 0.5-1.5 mm in 316L stainless, with maximum working width of 1,250 mm (SBAL-V-1250J) or 1,500 mm (SBAL-V-1500J), at a forming speed of 16 m/min. The line integrates uncoiling, levelling, beading, notching, shearing and TDF or angle flange forming in a U-shape layout with a compact 14,000 × 2,000 × 1,800 mm (or 14,000 × 2,200 × 1,800 mm) workshop footprint. Power 87 kW, weight 16 tons, 380V / 50Hz / 3PH. Surface finish 2B as standard, with 2B-DD upgrade for visible architectural duct on aerospace cleanroom applications.

SBAL-V auto duct line — galvanised variant for accommodation and amenity

The same SBAL-V Auto Duct Line in galvanised configuration is the workhorse for the accommodation, office, canteen, gymnasium, medical centre and general circulation portions of the aerospace facility scope. Throughput on a single shift covers the duct demand for a complete commercial MRO accommodation precinct. Coil width 1,250 mm or 1,500 mm covers all duct sizes encountered on the amenity scope. SMACNA Class 6 leakage is achievable through the integrated TDF flange production.

SB-ZF1500 automatic stitchwelder for crevice-free 316L extract

The SB-ZF1500 Automatic Stitchwelder produces the longitudinal welded seam required for crevice-free 316L stainless extract duct. The machine handles material thickness 0.8-3 mm with diameters from Φ150 to Φ1,500 mm and welded length 100-1,500 mm per cycle. Overall dimensions 2,500 × 1,000 × 2,350 mm, 380V / 50Hz / 3PH. The welded seam is the construction class required for the aerospace plenum, the autoclave room extract, the composite cleanroom HEPA supply and return, the anodising extract and the paint booth extract. The seam is internally smooth, free of crevice geometry, and accepts the pickle-passivation treatment that establishes the corrosion-resistant chromium oxide passive layer.

SBSF-1525 round tube flanging machine

The SBSF-1525 Round Tube Flanging Machine produces flanged round duct ends for the bolted joint construction used on industrial dust extract, kitchen exhaust and material-handling installations. The machine handles black steel 0.5-2 mm and stainless steel 0.5-2.5 mm, with flanging width 75-152 mm, processing diameter 100-2,000 mm, max weight capacity 360 kg, power 2.5 kW, weight 520 kg, overall dimensions 2,200 × 1,100 × 1,240 mm, 380V / 50Hz / 3PH. For aerospace applications the SBSF-1525 produces the flanges for the round-duct portion of the dust extract train, the engine test cell intake silencing duct and the composite trim-and-drill HEPA extract.

SBFB-1500 and spiral tubeformer scope

The SBFB-1500 spiral tubeformer fabricates round duct for the composite trim-and-drill HEPA extract, the aluminium-dust extract subject to NFPA 660 spark-resistant requirements, the engine teardown bay coolant mist extract and the various small-diameter circulation runs throughout the facility. Diameter range covers the full aerospace scope. Coil thickness is configurable for galvanised, 304L or 316L stainless construction. The four-roller drive section maintains the helical seam quality required for SMACNA leakage class compliance.

SBPC1500 plasma cutter for 316L

The SBPC1500 Plasma Cutter (models SBPC1500×4000 and SBPC1500×6100) handles cut-to-shape stainless gauge for transitions, takeoffs, custom fittings and the cleanroom HEPA terminal supply boxes. Processing range 1,500×4,000 mm or 1,500×6,100 mm. Thickness 0.4-8 mm. Processing speed 7-8 m/min. Power 12 kW. Weight 2,200 kg (4-metre) or 2,700 kg (6-metre). Overall dimensions 4,000×1,300×1,330 mm or 5,000×1,300×1,330 mm. 380V / 50Hz / 3PH. The plasma cutter is the upstream machine that prepares the developed-length blanks for the SBAL-V auto duct line and the welded fittings that the SB-ZF1500 stitchwelder produces.

SBLR-600 flexible duct line for non-aerospace amenity

The SBLR-600 Flexible Duct Forming Machine handles the small-volume flexible duct scope for the non-aerospace amenity portion of the facility (residential-scale air-conditioning in the accommodation block, light-commercial ducted air-conditioning in the office and canteen). The machine produces semi-rigid and flexible duct in aluminium foil with steel wire frame at diameter Φ80-Φ600 mm, with feed speed up to 65 m/min, mainframe dimension 3,500 × 1,200 × 1,810 mm, power 7 kW, 380V / 50Hz / 3PH. Flexible duct is not used in the aerospace process zones — the combustible-dust extract train, the cleanroom supply and the chemistry extract paths all require continuous metal construction.

Spark-resistant fans and NFPA 660 mandatory throughout

For the aluminium dust, composite dust, jet fuel Zone 1, and lithium battery extract paths, spark-resistant fans are mandatory throughout the train. SBKJ supplies the duct fabrication machinery; the fans themselves are sourced from specialist AMCA-rated fan suppliers (typically AMCA Class A, B or C depending on the dust risk). The NFPA 660 framework drives the fan selection, the explosion venting design and the bonded-static duct construction. Our engineering team coordinates with the fan supplier and the dust collector OEM to ensure that the duct geometry, the bonded-static path, the explosion venting locations and the fan selection are coherent across the train.

Aerospace welded fabrication scope

For the high-temperature engine test cell exhaust (refractory-lined section), the heavy-gauge engine intake silencer and the welded autoclave room nitrogen-purge plenum in 3-8 mm 316L stainless, the fabrication is performed by specialist welded-fabrication subcontractors with submerged-arc welding capability, post-weld heat treatment and pressure-vessel expertise. SBKJ supplies the lighter-gauge sheet-metal portion of the same project and coordinates with the welded-fabrication subcontractor on the project boundary.

Procurement, quality system and aerospace contractor accreditation

Australian aerospace HVAC procurement operates under a different framework from commercial construction. The customer's AS 9100, AS 9110 or AS 9120 certification flows down to the HVAC contractor on the controlled portion of the project, and the contractor's quality system has to integrate with the customer's audit programme.

AS 9100 design and manufacture flow-down

AS 9100 is the aerospace quality management system standard for organisations that design and manufacture products for the aviation, space and defence industry. The standard adds aerospace-specific requirements to ISO 9001 covering risk management, configuration management, process control, first article inspection, counterfeit parts prevention and supply chain management. An HVAC contractor working inside an AS 9100 customer's facility is part of the customer's quality system on the controlled portion of the project — the contractor's personnel access, the materials introduced into the controlled environment, the FOD control on the installation crew and the documented commissioning of paint booth airflows and clean room class are all evidence requirements that the customer needs from the HVAC contractor.

AS 9110 MRO flow-down

AS 9110 is the parallel standard for aerospace maintenance, repair and overhaul (MRO) organisations. The certificated commercial MRO bases at Brisbane (Qantas), Sydney (Qantas, Star), Avalon (Qantas), Melbourne (Qantas, Star) and Brisbane (Virgin) hold this. The HVAC scope on these bases is part of the certified facility scope and any HVAC modification is logged in the facility's continuing airworthiness management exposition or the equivalent CASR/EASA/FAA document.

AS 9120 distribution flow-down

AS 9120 is the standard for aerospace distributors and stockists. The Australian aerospace spares distributors operate under AS 9120 for the procurement, storage and dispatch of aerospace parts. The HVAC contractor on a spares storage facility upgrade or expansion project carries AS 9120 flow-down requirements on the environmental control of the storage area.

Boeing Materials Quality Standards and Airbus AIS

Boeing Materials Quality Standards (BMQS) and Airbus AIS standards add a further procurement-side requirement on materials of construction and surface finishes. The applicable BMQS or AIS document is identified by the customer at design stage, and the contractor confirms that the proposed materials of construction meet the document requirements. For aerospace HVAC duct, the BMQS and AIS overlay typically applies to the 316L stainless material certification, the surface finish specification and the welding process qualification on the welded extract scope.

ITAR and EAR export controls

Aerospace facilities aligned with US Boeing, Lockheed-acquired Sikorsky or other US-origin programmes carry ITAR (International Traffic in Arms Regulations) and EAR (Export Administration Regulations) controls. HVAC components and drawings inside the controlled envelope may carry export-controlled markings. The contractor's supplier vetting, drawing transmittal controls and contractor personnel screening have to integrate with the customer's export control programme.

FOD control on the installation crew

Foreign object debris (FOD) control is one of the most distinctive aerospace contractor disciplines. Any small item left inside an aircraft component — a screw, a rivet, a strip of tape, a hand tool — can cause structural failure or system malfunction in service. The HVAC contractor's installation crew operates under a documented FOD control programme with shadow boards, tool count-in and count-out at every shift, daily housekeeping and continuous training. The customer audit programme regularly verifies the contractor's FOD discipline.

Materials traceability

Every material introduced into the controlled environment is traceable to a documented source. The 316L stainless coil supplied to the SBAL-V auto duct line carries a mill certificate documenting the alloy composition, the heat-treatment condition and the surface finish. The certificate flows through the fabrication record to the installation record, and the customer retains the certificate as part of the facility quality file.

Australian Industry Capability content

Australian-fabricated 316L stainless ductwork to the SBKJ specification with a traceable mill certificate and a documented pickle-passivation finish meets the Australian Industry Capability (AIC) content requirements that apply to most large aerospace projects in Australia. AIC content is calculated across the supply chain, with Australian fabrication labour, Australian-installed insulation, and Australian-supplied materials all contributing to the AIC percentage. For the aerospace component manufacturers, the commercial MRO bases, and the major helicopter overhaul facilities, the AIC content target on the mechanical building services scope is typically 60 per cent or higher.

Commissioning and first-article documentation

Aerospace HVAC commissioning is more rigorous than commercial commissioning because the deliverables become evidence in the customer's quality audit. The commissioning programme on an aerospace project typically includes the following stages.

Pre-commissioning duct integrity testing

Every duct system is leakage tested per SMACNA HVAC Air Duct Leakage Test Manual or AS 4254.2 before plenum acceptance. The leakage class is set by the customer specification — typically SMACNA Class C or tighter for the aerospace process extract paths, and SMACNA Seal Class A on the welded crevice-free 316L stainless construction. The leakage test is performed at the design pressure and the leakage rate is documented per ductwork section.

Paint booth face velocity verification

The aerospace paint booth is commissioned per AS 4114, with face velocity measurements at the operator station, at the booth corners and at the booth floor grating. The measurements are recorded against the design face velocity and against the supplier's data sheet. The first-article inspection is signed off by the customer and forms the baseline for periodic re-verification.

Isocyanate scrubber efficiency

The paint booth activated carbon scrubber efficiency is verified by air sampling upstream and downstream of the carbon stage during a representative paint cycle. The measured efficiency is recorded and is the baseline for the periodic carbon replacement schedule.

Cr(VI) personal monitoring at the anodising line

The Cr(VI) extract at the anodising line is commissioned by personal monitoring on the operators during a representative anodise cycle. The personal monitoring sample is analysed against the Safe Work Australia WES of 0.005 mg/m³, with documentation flowing into the customer's hazardous substance register.

Aluminium dust Kst verification

The aluminium dust extract system is commissioned by dust sampling at the collector inlet and at the duct cross-section, with the dust composition and the Kst confirmed against the design assumptions. The spark detection and suppression system is functionally tested with a controlled ignition source upstream of the collector, with the documented response time recorded against the design specification.

HEPA filter integrity testing

The composite cleanroom HEPA H13 supply and the composite trim-and-drill HEPA H13 extract are integrity tested per ISO 14644-3 or the equivalent customer specification. The integrity test is performed at the installation stage and at periodic intervals during the operating life of the facility.

Cleanroom class qualification

The composite layup cleanroom is qualified per ISO 14644-1 at the design occupancy and operating condition. The qualification covers the particulate count, the recovery time, the temperature stability, the humidity stability and the ESD performance. The qualification report is the baseline document for the cleanroom operating life.

First-article inspection report

The first-article inspection (FAI) report consolidates the design, fabrication, installation and commissioning evidence into a single contract deliverable. The FAI report is signed by the contractor, the customer's mechanical consultant and the customer's quality engineer, and is retained as the audit-of-record document for the facility.

How SBKJ supports Australian aerospace HVAC contractors

SBKJ Group operates from Box Hill North Victoria as the Australian arm of the SBKJ international machine-supply business. We support aerospace HVAC contractors across four engagement modes that align with the procurement structure on Australian aerospace projects.

Auto duct line and welded duct machinery supply

The principal commercial relationship is the supply of SBAL-V auto duct lines (galvanised and 316L stainless variants), SB-ZF1500 automatic stitchwelders, SBSF-1525 round tube flangers, spiral tubeformers, SBPC1500 plasma cutters and SBLR-600 flexible duct lines into the contractor's fabrication workshop. We install, commission and maintain the machinery, with operator training and lifetime spare-parts availability included as standard. The machine selection is matched to the contractor's portfolio — an aerospace component manufacturer fabricator needs a different machine set from a commercial MRO fabricator from a general aviation hangar specialist.

Engineering consultation on duct specification and material selection

SBKJ engineers have 30+ years of cumulative experience across aerospace, defence, marine, cleanroom and hazardous-area facility work. Where an aerospace specification requires resolution between the SMACNA, AS/NZS 4254, EN 1505 and ISO 14644 standards, or where the Cr(VI) extract design has to coordinate with the Boeing BMQS or the Airbus AIS material specification, our engineers provide the cross-walk and the technical resolution.

Sub-supply through aerospace prime contractors

SBKJ machinery and engineering services are routinely supplied through aerospace prime contractors who hold the head AS 9100 or AS 9110 accreditation and the contractual relationship with the end customer. This is the dominant mode for the Boeing Aerostructures Australia, Quickstep, Qantas Engineering, Sikorsky Australia and major helicopter overhaul facility scope. The prime contractor manages the customer-facing quality system and the SBKJ machinery sits in the contractor's fabrication shop as a documented production resource.

Coordination with specialist subcontractors on aerospace welded scope

For the heavy-gauge engine test cell exhaust (refractory-lined section), the heavy-gauge engine intake silencer and the welded autoclave room nitrogen-purge plenum in 3-8 mm 316L stainless, the fabrication is outside SBKJ's machinery scope and is performed by specialist welded-fabrication subcontractors. We coordinate the project boundary between the lighter-gauge sheet-metal scope (SBKJ machinery) and the heavier-gauge welded scope (specialist subcontractor) to ensure clean integration on site.

FAQ

Why does aerospace HVAC need 316L stainless in so many places where commercial uses galvanised?

Aerospace concentrates chemistries that destroy zinc within months and corrode 304 stainless within years. Hex-chrome from anodising, sulphuric acid mist, chloride, reduced-sulphur from JP-8, isocyanate condensate from paint booth extract and chrome plating mist all require 316L with welded crevice-free seams and pickle-passivation. The Cr(VI) WES of 0.005 mg/m³ and the isocyanate STEL of 0.005 ppm are among the lowest in the Australian WES schedule and the duct is part of the emission-control loop.

What is AS 9100, AS 9110 and AS 9120 and why do they matter to an HVAC contractor?

AS 9100 is aerospace QMS for design and manufacture, AS 9110 for MRO, AS 9120 for distribution. The HVAC contractor is not building aircraft but feeds the customer's audit on the controlled portion of the project. FOD control on the installation crew, traceability of introduced materials and documented commissioning of paint booth and cleanroom airflows are all evidence requirements.

How is aluminium dust handled under NFPA 660 and AS 3957?

Aircraft alloys 7075, 2024 and 2014 generate Kst 200+ St3 combustible dust. NFPA 660 and AS 3957 drive spark-resistant fans, continuous metal duct, NFPA 68 explosion venting, no flexible duct in the dust train, bonded-static path and wet collection where inventory exceeds threshold. The WES is 1 mg/m³ respirable but deflagration risk governs the design first.

What HVAC class is required for an aerospace composite layup cleanroom?

ISO 7 (Class 10,000) with HEPA H13 ceiling supply at 0.20-0.30 m/s downflow, ESD protection, 20-22°C, 30-55 per cent RH, 316L stainless welded ductwork. The autoclave is a separate adjacent zone — not inside the cleanroom — because it runs at 180-220°C, 7-14 bar nitrogen and is incompatible with cleanroom airflow.

Why is the autoclave cure room separate from the layup cleanroom?

Autoclaves cure prepreg at 180-220°C and 7-14 bar nitrogen pressure. The room manages heat rejection from the autoclave shell, nitrogen displacement of breathable air, possible epoxy off-gassing in failed-cure, and explosion-relief venting. Putting that inside a Class 10,000 cleanroom destroys the cleanroom envelope every cure. Separate AS 1668.2 zone with 6-10 ACH, oxygen depletion monitoring 19.5 per cent O2 minimum, emergency nitrogen purge, 316L stainless duct.

What is the HVAC scope for an aircraft livery paint booth?

AS 4114 downdraft, 0.5 m/s face velocity, ceiling plenum supply at low velocity, floor-grating extract, three-stage filtration (paint arrestor, activated carbon, HEPA H13), 316L stainless extract duct. Isocyanate WES STEL 0.005 ppm. Operators wear supplied-air respirators — the HVAC protects the surrounding facility, not the painter. Paint mix room is AS 1940 Zone 2.

How does general aviation hangar HVAC differ from commercial wide-body MRO?

General aviation hangar is 1,000-4,000 m² single-storey shed with limited mechanical ventilation, intermittent fuelling and no permanent painting. Commercial wide-body MRO is 20,000-40,000 m² with continuous 6-10 ACH, NFPA 409 Class I or II, foam suppression, paint shop and engine test cells, 24/7 operation. Duct quantity ratio is 30:1 or higher.

What materials and machinery does SBKJ recommend for an Australian aerospace HVAC contractor?

316L stainless on SBAL-V auto duct line for anodising, chromate conversion, paint booth, plating, autoclave, composite cleanroom and hex-chrome scrubber. SB-ZF1500 automatic stitchwelder for welded crevice-free extract. SBSF-1525 round flanger and spiral tubeformer for composite trim-and-drill HEPA and aluminium dust extract with spark-resistant fans and NFPA 660. SBPC1500 plasma cutter for 316L cut-to-shape. SBLR-600 flexible duct for non-aerospace amenity. Galvanised SBAL-V for accommodation, office, canteen.

12-hour reply

Specifying HVAC ductwork for an aerospace component manufacturer, commercial MRO base, general aviation hangar, helicopter overhaul facility or aerospace composite layup project? An SBKJ aerospace-sector engineer replies within 12 hours — not a salesperson.

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