Why composite manufacturing HVAC is unique
Composite manufacturing is one of the most HVAC-demanding manufacturing categories in industry — and it is one of the categories where ductwork specification mistakes show up fastest as compliance findings, worker exposure events, and product rejection at quality acceptance. Composite plants do not behave like sheet-metal shops or general assembly factories. They behave like a hybrid between a chemical process plant, a clean room, a heated process oven, and a precision machining shop, with all four operating in adjacent zones in the same building.
There are five HVAC challenges that define a composite manufacturing facility, and an HVAC ductwork specification that does not address all five will fail commissioning or fail compliance audit within the first two years of operation.
VOC and styrene exhaust at the open-mould lay-up bench. Polyester and vinyl ester wet lay-up release styrene during gel-coat application, lay-up and cure. Styrene is a potent respiratory irritant and a possible carcinogen. The ACGIH Threshold Limit Value 8-hour TWA is 20 ppm — five times stricter than the OSHA Permissible Exposure Limit of 100 ppm — and the ACGIH limit is the de facto international design target on any new composite lay-up shop. Capturing styrene at source, rather than diluting it with general ventilation, is the only economically sustainable approach.
Carbon fibre dust from machining cured composite. Trim, drill, route and grind operations on cured carbon fibre reinforced polymer release respirable dust that is conductive, abrasive and a respiratory plus skin irritant. Conductive dust shorting electrical equipment is a well-documented failure mode in carbon fibre finishing shops with poorly specified dust extraction. The dust is heavier than air but fine enough to remain airborne for hours without mechanical extraction.
Autoclave thermal management. Aerospace-grade autoclaves operate at 180°C and 7 bar internal pressure for 4–8 hour cure cycles. The external surface, even with lagging, radiates 8–15 kW of thermal load per cubic metre of autoclave internal volume during the heat-up phase. The autoclave room HVAC has to remove that heat, and it has to keep the autoclave control electronics within their qualified operating envelope.
Lay-up clean room cleanliness, temperature and humidity stability. Pre-preg material handling rooms run at ISO 14644 Class 8 cleanliness or stricter, 18–22°C, 40–65% RH, with very low air velocity at the lay-up surface so dust is not stirred up off the bench. Pre-preg out-life is a finite clock that starts at first thaw — every degree of temperature drift shortens it.
Worker chemical exposure compliance. Composite manufacturing has multiple regulated exposure routes — styrene inhalation, carbon fibre dust inhalation and skin contact, isocyanate exposure during paint, solvent exposure during tooling work, and noise exposure at autoclave and dust collector locations. HVAC ductwork is one of the primary engineering controls for each of these, and a poor specification cascades into PPE escalation and job-rotation requirements that crater throughput.
This guide walks through every one of these challenges by zone — from pre-preg cold storage to final paint — and gives the duct material, sizing and commissioning specifications that an experienced composite plant HVAC engineer would write into a tender pack.
Composite types and processes — what each one demands from HVAC
Composite manufacturing is not a single process. The HVAC implications of each combination of fibre type and process are materially different, and a duct specification that treats them as identical will overspecify for some zones and dangerously underspecify for others.
Fibre and matrix systems
Carbon fibre reinforced polymer (CFRP). Used for aerospace primary structure, premium automotive, motorsport, performance sporting goods and a growing share of wind blade spar caps. Cured CFRP machining releases conductive carbon dust. Wet lay-up CFRP with epoxy resin has lower VOC release than polyester systems. Pre-preg CFRP is the dominant aerospace process and is associated with the strictest HVAC requirements.
Glass fibre reinforced polymer (GFRP/fibreglass). Used for wind turbine blade shells, marine hulls, swimming pools, storage tanks and infrastructure. Wet lay-up GFRP with polyester or vinyl ester resin is the largest single source of styrene emissions in composite manufacturing. Glass fibre dust from machining is less conductive than carbon but is still a respiratory and skin irritant.
Aramid (Kevlar and equivalents). Used for ballistic protection, aerospace secondary structure and some sporting goods. Aramid dust is fibrous and produces long airborne fibres during cutting — the fibres do not fracture cleanly and require dedicated extraction with appropriate filter media.
Hybrid laminates. Carbon-glass, carbon-aramid and carbon-glass-aramid hybrid laminates are common in defence applications, including some submarine pressure hull testing articles and surface ship structural panels. Hybrid laminates produce mixed dust streams that have to be evaluated against the strictest of the three constituent dust profiles.
Process types
Pre-preg lay-up. Pre-impregnated fibre with B-stage resin is laid up by hand or by automated tape laying machines, then cured in autoclave or out-of-autoclave oven. Lowest VOC release of the major composite processes — pre-preg resin is at low volatility B-stage. HVAC focus is cleanliness, temperature and humidity stability, and out-life management.
Wet lay-up. Liquid resin applied to dry fibre by hand, often with gel coat surface. Highest VOC release, particularly when polyester or vinyl ester resin is used. HVAC focus is source capture of styrene and worker breathing zone control.
Resin Transfer Moulding (RTM). Closed-mould process — dry fibre placed in a closed mould, resin injected under pressure, cured. Lower VOC release than open-mould wet lay-up because the resin is contained, but mould release agents and demoulding operations still generate some VOC. Heated mould tools require cooling for the surrounding workspace.
Resin infusion (VARTM, SCRIMP). Vacuum-assisted resin transfer moulding and similar processes — dry fibre under a vacuum bag, resin drawn in by vacuum, cured. Common for wind blade shells and large marine structures. VOC release is intermediate between wet lay-up and closed RTM.
Filament winding. Continuous fibre wound onto a rotating mandrel with resin bath. Used for pressure vessels, pipe, drive shafts and some pressure hull structures. VOC release similar to wet lay-up but localised at the resin bath. Filament winding shops are typically lower-VOC than open-mould lay-up shops.
Pultrusion. Continuous fibre pulled through a resin bath and a heated die. Industrial application — rebar, structural shapes, infrastructure. VOC release at the resin bath and at the die exit.
Each combination of fibre and process drops into a different HVAC duty profile. The guide that follows walks through the duty profiles by zone rather than by process — most composite plants run multiple processes in adjacent zones, and the HVAC specification has to handle the full mix.
End uses driving composite manufacturing growth
Understanding where composite demand is growing is essential to scoping HVAC duct machinery for the next decade. Five end-use sectors dominate the project pipeline.
Aerospace primary structure
Aerospace is the largest single driver of pre-preg CFRP capacity globally. The Boeing 787 Dreamliner is approximately 50% composite by weight, with the fuselage barrel and wing primary structure in pre-preg CFRP. The Airbus A350 follows a similar architecture at 53% composite by weight. Both programmes drove a wave of composite manufacturing capacity expansion at Boeing Everett WA and Charleston SC, Airbus Hamburg and Toulouse, an Airbus Asian assembly facility, Spirit AeroSystems Wichita, GKN Aerospace and tier-one suppliers globally.
Modern aerospace composite plants are characterised by very large autoclaves — the Boeing 787 fuselage barrel autoclaves at Everett are among the largest production autoclaves in the world, running 4–8 hour cure cycles on parts up to 6 metres in diameter. The HVAC challenge is industrial-scale autoclave thermal management combined with very strict ISO 8 lay-up clean room cleanliness for primary structure pre-preg lay-up.
Defence aerospace
The Lockheed Martin F-35 Lightning II programme uses extensive CFRP for wing and empennage structure, with Northrop Grumman building the centre fuselage and Lockheed Martin Aeronautics Fort Worth running the final assembly. F-35 sustainment and modification work is bringing additional composite capacity to partner nations, including Australian industry under the F-35 Global Sustainment programme. The Boeing F-15EX, F/A-18 sustainment and the next-generation air dominance programmes all carry significant composite content.
Wind turbine blades
Wind blade manufacturing is the largest single tonnage consumer of composite material globally. Vestas, Siemens Gamesa, GE (LM Wind Power), Goldwind and Nordex collectively produce tens of thousands of blades per year, with blade lengths now reaching 115 metres for the largest offshore turbines. Wind blade factories are characterised by very long, low buildings — up to 120 metres long for a single moulding bay — with HVAC distributed along the length of the building. VOC capture at the open-mould infusion bay and the gel coat application station is the dominant HVAC challenge.
Vestas, Siemens Gamesa Cuxhaven Germany, Siemens Gamesa Hull UK, GE Onshore and Offshore (LM Wind Power), and Nordex Rostock are representative facilities. In Australia, Vestas has announced a wind blade factory at Burnie Tasmania, and additional wind turbine OEMs are evaluating Australian factory locations to support the Commonwealth Renewable Energy Zone programme and the offshore wind targets in Bass Strait, Illawarra, Hunter and Gippsland.
Defence ground vehicles, naval and submarine
Modern naval and submarine programmes use composite for sonar dome housings, propulsion train fairings, internal compartmentation, ballistic panels and pressure hull testing articles. The AUKUS Optimal Pathway announced in March 2023 commits Australia to a Virginia-class and SSN-AUKUS class submarine programme based at Henderson WA and Adelaide SA. The composite content on a single submarine is hundreds of tonnes of structural and acoustic composite, and the AUKUS Optimal Pathway is driving multiple new composite manufacturing capacity announcements at Australian sites. Surface ship programmes including the Hunter-class frigate at Osborne South Australia carry significant composite content.
BAE Systems composites in Australia, Quickstep Holdings (Bankstown New South Wales and Geelong Victoria), Marand Precision Engineering, Boeing Aerostructures Australia (Port Melbourne and Fishermans Bend), Lovitt Technologies and CSIRO Manufacturing collectively form the established Australian composite manufacturing base that is now expanding to support AUKUS, F-35 sustainment, Hunter-class frigate composite content and the Commonwealth-funded Sovereign Industrial Capabilities priorities.
Premium automotive and motorsport
BMW i3 and i8 — the original carbon fibre passenger car programme — drove a wave of automotive CFRP capacity at SGL Automotive Carbon Fibers Moses Lake WA and the BMW Landshut and Wackersdorf composite plants. Lamborghini Sant'Agata, McLaren Composites Technology Centre Sheffield UK, Koenigsegg, Pagani and the major motorsport tier-ones run continuous CFRP lay-up at smaller scale but with very strict aerospace-grade quality control. Premium automotive OEMs continue to integrate carbon fibre into structural applications including monocoques, body panels, suspension components and wheels.
Marine
Premium yacht builders, fast ferry builders, and high-performance racing boat builders run continuous open-mould and infusion lay-up at scale. Marine composite plants are typically the largest single source of styrene emissions in any composite category — large hull infusion processes can release tens of kilograms of styrene per shift if uncontrolled. HVAC source capture at the lay-up bay is the dominant compliance issue for marine composite manufacturers.
Sporting goods and infrastructure
Cycling frames, golf shafts, tennis rackets, ski and snowboard cores, fishing rods and the broader sporting goods category drive a meaningful share of CFRP capacity in regional manufacturing hubs. Infrastructure applications — bridge cable, FRP rebar, pultruded structural shapes, composite pipe — are a slower-growing but expanding category.
Key standards and exposure limits
Composite manufacturing HVAC sits at the intersection of multiple standards frameworks. The HVAC engineer should have working familiarity with all of them and should know which one is the binding compliance reference for the project's jurisdiction.
NFPA 33 — Standard for Spray Application Using Flammable or Combustible Materials. Applies to spray gel coat, spray gun resin application and spray paint operations in composite plants. NFPA 33 sets exhaust ventilation, electrical hazardous area classification and fire suppression requirements for spray application zones. The standard is the foundation for compliant gel coat booth design.
NFPA 91 — Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Particulate Solids. Applies to the exhaust ductwork itself — material selection, construction, fire dampers, cleanouts and inspection. Composite plant VOC and dust exhaust ductwork is designed to NFPA 91.
NFPA 86 — Standard for Ovens and Furnaces. Applies to OOA cure ovens, post-cure ovens and pre-preg thaw ovens. Sets exhaust requirements, gas train requirements for fuel-fired ovens, and interlock requirements between heating and exhaust.
NFPA 484 — Standard for Combustible Metals. Reference framework for combustible dust analysis on mixed-dust shops where carbon fibre dust is processed alongside metal grinding or coating residues.
OSHA 29 CFR 1910.1000 — Air Contaminants. Sets US Permissible Exposure Limits. Styrene 8-hour TWA is 100 ppm with 200 ppm ceiling. Methylene chloride and other solvents commonly found in composite plants have separate OSHA-regulated PELs.
NIOSH Recommended Exposure Limits. NIOSH REL for styrene is 50 ppm 8-hour TWA — half the OSHA PEL. NIOSH carbon nanofibre and carbon nanotube REL is 1 microgram per cubic metre on a respirable mass basis, which is relevant to the more advanced CFRP nanocomposite programmes.
ACGIH Threshold Limit Values. ACGIH TLV for styrene is 20 ppm 8-hour TWA — five times stricter than OSHA. ACGIH publishes the Industrial Ventilation Manual, and the chapter on plastics manufacturing is the de facto international reference for composite plant local exhaust ventilation design. Capture velocities in the IV Manual are the working numbers used by HVAC consultants on composite projects worldwide.
AS 1668.2 — The use of ventilation and airconditioning in buildings — Mechanical ventilation in buildings. The Australian general dilution ventilation framework. Sets minimum outside air rates and contaminant control approach. Does not replace ACGIH-derived capture velocities but is the binding document for general ventilation in Australian composite plants.
AS/NZS 3000 — Electrical installations (Wiring Rules). Sets Australian electrical hazardous area classification framework, working with AS/NZS 60079. Polyester and vinyl ester open-mould zones may require Zone 2 hazardous area classification for the immediate lay-up bay.
AS/NZS 4254 — Ductwork for air-handling systems in buildings. The Australian and New Zealand HVAC ductwork construction standard — pressure classes, materials, sealing classes, support and access. Equivalent to SMACNA HVAC Duct Construction Standards in the US market and DW/144 in the UK.
ISO 14644 — Cleanrooms and associated controlled environments. Sets the cleanliness class system used to specify pre-preg lay-up rooms. ISO Class 8 is the typical baseline for aerospace primary structure pre-preg lay-up.
BS EN 16275 — Fixed technical equipment in industrial applications — Vacuum cleaners with filtering for combustible dusts. Reference for combustible dust extraction equipment, including dust collectors serving carbon fibre and mixed-dust finishing shops.
Lay-up clean room HVAC
The pre-preg lay-up clean room is the most HVAC-demanding zone in a typical composite manufacturing facility. The HVAC specification has to deliver four things simultaneously: ISO 14644 Class 8 cleanliness, 18–22°C temperature with ±2°C stability, 40–65% RH with ±5% stability, and very low air velocity at the lay-up surface to prevent dust stir-up off the bench.
Class 8 cleanliness — 3.5 million particles per cubic metre at 0.5 micron, equivalent to a Class 100,000 federal standard — is achieved through filtered supply air, positive pressure relative to surrounding spaces, and a controlled gowning protocol. The HVAC ductwork supplying the lay-up room is typically 304L stainless steel internally polished, or epoxy-coated galvanised steel, with low-leakage TDF or proprietary clean-room flange connections. Galvanised duct with butyl tape sealant is not appropriate for a Class 8 lay-up room because the gasket releases particulate over time.
The temperature and humidity stability bands are tighter than typical commercial HVAC and require a dedicated air handling unit with chilled water cooling, hot water reheat, and either a steam humidifier or a wet-cell humidifier sized for the latent load. Simple direct expansion split systems do not deliver the stability required.
The low surface velocity requirement — typically below 0.25 m/s at the lay-up bench — drives the diffuser specification. Ceiling-mounted fabric diffusers (sock diffusers) or large-area perforated diffusers are the common choice. Standard four-way blow ceiling diffusers create local high-velocity zones that disturb dry carbon fabric and stir dust off the bench surface. The supply ductwork to the diffusers should be sized for low velocity (typically 5–7 m/s in main runs, 3–4 m/s in branch runs to the diffusers).
Pre-preg out-life management is the operational driver for temperature stability. Most aerospace pre-preg systems are qualified for 30 days out of freezer at 21°C — every degree above 21°C accelerates resin advancement and shortens qualified out-life. A single HVAC failure event that pushes the lay-up room above 24°C for several hours can void the qualified out-life on every roll of pre-preg in the room, and the resulting scrap cost can run to hundreds of thousands of dollars on a busy lay-up floor.
Open mould wet lay-up HVAC
Open-mould wet lay-up is at the opposite end of the HVAC spectrum from pre-preg lay-up. The dominant challenge is VOC and styrene capture at source, with breathing zone exposure control as the binding compliance constraint.
The ACGIH Industrial Ventilation Manual chapter on plastics manufacturing gives capture velocities for open-mould lay-up of 0.5–1.5 m/s at the boundary of the styrene release plume, depending on the resin system, application method and adjacent air movement. Source capture is implemented through one of three approaches: a back-draught wall behind the lay-up station, a side-draught hood on a long hull lay-up, or a downdraught grating in the floor for parts that have to be accessed from all sides. Each approach has trade-offs.
The exhaust ductwork from open-mould lay-up zones is one of the most chemically aggressive duty cycles in any composite plant. Styrene-laden air at 5–50 ppm continuously corrodes mild steel and degrades standard butyl gasket tape within months. The two viable material specifications are fibreglass-reinforced plastic (FRP) duct or polypropylene-lined steel duct. Stainless steel is acceptable but is more expensive and offers no compelling chemical advantage over FRP for styrene service.
General dilution ventilation for the lay-up shop runs at 6–12 air changes per hour, depending on shop geometry and resin throughput. The dilution component is necessary because source capture is never 100% efficient — even a well-designed back-draught wall captures 70–85% of styrene release, with the balance escaping into the general shop atmosphere.
Fire and explosion considerations apply. Styrene has a lower explosive limit of approximately 1.1% in air, well above typical workplace concentrations, but elevated styrene concentrations near gel coat spray operations have to be evaluated against AS/NZS 60079 hazardous area zoning. NFPA 33 sets the framework for spray application zones in the US, and equivalent treatment under AS/NZS 60079 applies in Australian plants. Hazardous area zoning affects electrical equipment selection, including lighting, motor controls and dampers, in the immediate lay-up zone.
Closed mould RTM and infusion HVAC
Closed-mould resin transfer moulding and resin infusion processes are intermediate between pre-preg lay-up and open-mould wet lay-up on the HVAC duty spectrum. The resin is contained inside a closed mould or under a vacuum bag during cure, so styrene release during the cure phase is much lower than open mould. Mould release agent application, vacuum bag preparation and demoulding still generate VOC release, but at lower magnitude.
The dominant HVAC challenge in RTM and infusion zones is heated mould cooling. Many RTM and infusion processes use heated tooling at 60–120°C to reduce cure time. The heat from the heated mould is rejected into the surrounding workspace and accumulates rapidly without dedicated extraction. A typical RTM cell with a 2 m² heated tool at 80°C rejects approximately 4–8 kW of thermal load to the surrounding air during the cure phase. Multiplied across a six-cell RTM bay, the combined thermal load is comparable to a small autoclave hall.
HVAC ductwork to RTM and infusion zones is typically galvanised G90 for general supply, with dedicated extraction over each heated mould station. The extraction ductwork is galvanised or 304L stainless and should be evaluated against the operating temperature of the heated mould — extraction air directly above the mould can run at 50–80°C during the cure phase.
Autoclave hall HVAC
Aerospace and high-end industrial composite manufacturing centres on the autoclave. A production autoclave for a 4 metre diameter, 12 metre long composite part is a substantial pressure vessel — internal volume in the order of 150 cubic metres, operating at 180°C and 7 bar during the cure cycle, with a 4–8 hour cycle time. The HVAC engineer is dealing with three thermal management problems in the autoclave hall.
Autoclave external surface heat rejection. Even with industrial lagging, the external surface of a production autoclave radiates 8–15 kW per cubic metre of internal volume during the heat-up phase. For a 150 m³ autoclave, peak thermal rejection is 1.2–2.2 MW. The autoclave hall HVAC has to remove this thermal load to keep the workspace within acceptable worker comfort limits — typically below 28°C dry bulb at the operator working position.
Control electronics conditioned space. The autoclave control system, including the PLC, the thermocouple input multiplexers, the pressure transducers and the recipe storage, has to operate within a much tighter temperature envelope than the surrounding hall — typically 18–24°C. This is delivered through a separately conditioned electronics room or a conditioned cabinet adjacent to the autoclave.
Loading bay vapour exhaust. When the autoclave door opens at the end of the cure cycle, residual solvent vapour, unreacted resin volatiles and the inert gas blanket (typically nitrogen) are released into the loading bay. A dedicated loading bay exhaust hood above the door, operating at high capture velocity for the door-opening phase, is the standard control. The exhaust ductwork is 304L stainless steel because of the temperature spike at door opening — the released air is at 60–100°C as the autoclave depressurises.
General autoclave hall ventilation runs at 6–10 air changes per hour, supplemented by spot cooling at operator working positions. Air handling units serving the autoclave hall are typically sized at 2–3 times the comfort cooling load to handle the peak heat rejection during autoclave heat-up cycles.
OOA cure oven HVAC
Out-of-autoclave (OOA) cure ovens are an alternative to autoclave cure for some pre-preg systems, particularly the newer generation of toughened epoxy resins that cure under vacuum bag pressure alone without the additional autoclave pressure. OOA ovens are simpler and cheaper than autoclaves but introduce different HVAC challenges.
OOA ovens are heated process equipment under NFPA 86 in the US market, with equivalent treatment under AS/NZS 4214 in Australia. The standard sets the framework for hot air supply, vapour exhaust during cure, and interlocks between the heating system and the exhaust system.
The exhaust leg from an OOA cure oven carries solvent vapour, binder vapour and water vapour released from the curing pre-preg. The exhaust temperature is typically 60–100°C during the cure phase, dropping back to ambient during the cool-down. The ductwork specification is 304L stainless steel for the high-temperature section closest to the oven, transitioning to galvanised on the cooler downstream runs. NFPA 91 governs the exhaust ductwork construction.
OOA cure oven HVAC is typically integrated with the broader autoclave hall HVAC because the two zones are usually adjacent and share thermal rejection paths. Larger composite plants may dedicate a separate OOA hall.
Trim and finishing HVAC — carbon fibre dust extraction
Trim, drill, route, sand and grind operations on cured composite parts produce one of the most challenging dust streams in industrial manufacturing. Carbon fibre dust from machining cured CFRP is conductive, abrasive, fibrous and a respiratory plus skin irritant. Glass fibre dust is less conductive but is still a respiratory and skin irritant. Aramid dust is fibrous with long airborne fibres that do not fracture cleanly.
Three rules govern the HVAC specification.
Rule one — source capture at every machining tool. Hood face velocity sized per ACGIH Industrial Ventilation Manual chapter on plastics manufacturing, typically 0.5–1.0 m/s for routing and trimming, 1.0–2.0 m/s for drilling, 2.0–2.5 m/s for grinding and abrasive operations. Capture at source is the only economically sustainable control — once dust escapes the machining tool it is dispersed across the building and recovery becomes orders of magnitude harder.
Rule two — HEPA H13 or H14 final filtration mandatory. Carbon fibre dust at the respirable size fraction (below 5 microns) is the fraction that reaches deep lung tissue. HEPA H13 filtration at 99.95% efficiency on 0.3 micron particles is the minimum acceptable specification before any return air is recirculated or before extracted air is discharged to atmosphere. H14 at 99.995% is a common upgrade for newer plants.
Rule three — combustible dust evaluation. Bare dry carbon fibre dust is not strongly combustible — it has a high ignition energy and does not propagate flame readily in most conditions. But mixed-dust shops, where carbon fibre dust mixes with metal grinding residue, paint over-spray or coating residue, can produce explosive dust mixtures. The framework is BS EN 16275 in Europe and NFPA 484 (with NFPA 654) in the US. Dust collectors serving mixed-dust shops are typically explosion-rated — vented to atmosphere through a deflagration vent, with isolation valves on the inlet ductwork.
The ductwork specification for carbon fibre dust extraction is antistatic-treated galvanised steel or 304L stainless steel with bonded electrical grounding for static dissipation. Carbon fibre dust accumulates electrostatic charge as it travels through the duct, and ungrounded duct sections can build up static potential that discharges through the dust cloud — the worst case scenario in a combustible dust line.
Duct velocity in the dust extraction system is in the 18–22 m/s range — high enough to transport the dust without settling, low enough to limit abrasive wear on the duct wall. Long radius elbows are mandatory; short radius elbows wear out in months of service on high dust loads. Cleanout doors at every change of direction and at every 6 metres of straight run are specified per NFPA 91.
Filament winding HVAC
Filament winding shops have a lower VOC duty than open-mould wet lay-up because the resin release is localised at the resin bath rather than spread across a large lay-up surface. The dominant HVAC challenge in filament winding is worker comfort and general dilution ventilation.
HVAC specification is similar to a general light industrial workshop — galvanised G90 supply ductwork, 6–10 air changes per hour, exhaust localised over the resin bath. Source capture at the resin bath is sized per ACGIH IV Manual capture velocities for liquid surface release.
Filament winding shops producing pressure vessels for hydrogen storage or compressed natural gas have additional safety considerations because the wound part is a pressure vessel. The HVAC specification does not change materially but the electrical hazardous area zoning may extend further than a general filament winding shop.
Pre-preg cold storage HVAC
Pre-preg material has a finite shelf life that extends from a few weeks to several months at -18°C and a few days to a few weeks at 21°C. Every roll of pre-preg arrives at the plant with a date of manufacture and a documented out-life clock. The cold storage HVAC has to maintain -18°C with low humidity to extend qualified shelf life.
The cold storage room is a separate refrigerated package — typically a walk-in cold room with insulated panel construction, dedicated refrigeration unit, and a vestibule or air curtain at the entry to limit moisture infiltration during access. Low humidity is critical — high humidity in cold storage causes ice formation on the pre-preg roll surface during freeze, and condensation on the roll surface during thaw.
Adjacent to the cold storage is a thaw room or thaw workstation where pre-preg rolls are warmed to room temperature in their sealed bag before opening. Opening a cold roll directly into the lay-up room causes condensation on the cold pre-preg surface, contaminating the resin. The thaw room is typically held at 18–22°C with 30–50% RH and is sized for the daily pre-preg consumption rate.
Cold storage HVAC ductwork is typically insulated galvanised steel with vapour barrier — pre-insulated panel duct is acceptable for the supply leg. The refrigeration package is sized for the door-opening cycles and the latent load from any incoming pre-preg rolls.
Tooling room HVAC
Master patterns and production tools for composite manufacturing are typically large composite or invar structures that have to be manufactured to very tight dimensional tolerance. Tooling rooms are held at 22°C ±2°C for dimensional stability — a 6 metre composite tool changes dimension by approximately 0.3 mm per °C of temperature drift, which is significant on aerospace tolerance work.
Tooling room HVAC is typically specified to the same standard as the lay-up clean room — 304L stainless or epoxy-coated galvanised ductwork, low-velocity supply at the working surface, ISO 8 cleanliness as a baseline (some tooling rooms are stricter). Tooling repair and maintenance operations may include grinding, machining and bonding, each of which requires localised exhaust capture.
Materials specification by zone
The single most common rework item we see at composite plant HVAC commissioning is a duct material specification that does not match the duty. The five zone categories below cover the typical specification matrix.
General supply and return air — galvanised G90 to AS/NZS 4254 or SMACNA. Standard galvanised duct construction for general HVAC supply and return outside the high-duty zones. Pressure class typically 500 Pa positive, 250 Pa negative. Sealing class C or B per AS/NZS 4254.
Lay-up clean room and tooling room — 304L stainless internally polished or epoxy-coated galvanised. The cleanliness duty rules out standard galvanised with butyl gasket tape because the gasket releases particulate over time. 304L stainless is preferred for new aerospace plants; epoxy-coated galvanised is acceptable for less stringent applications.
Open-mould VOC and styrene exhaust — fibreglass-reinforced plastic (FRP) duct or polypropylene-lined steel. The chemical duty rules out bare galvanised. FRP duct is the preferred choice for new construction because it is inherently chemical-resistant. Polypropylene-lined steel is acceptable but introduces a liner-to-steel bond inspection requirement at ten-year intervals.
Carbon fibre dust extraction — antistatic-treated galvanised or 304L stainless with bonded grounding. The static dissipation requirement rules out FRP and polypropylene-lined duct, both of which are electrical insulators. Antistatic-treated galvanised is the standard choice. 304L stainless is an upgrade for premium applications.
Autoclave loading bay exhaust — 304L stainless rated for the temperature spike at door opening. The temperature duty rules out standard galvanised because the zinc coating begins to volatilise at sustained 200°C operation. 304L stainless handles the door-opening spike comfortably and tolerates the chemical duty from residual solvent vapour.
Major composite manufacturing facilities globally
The major composite manufacturing capacity in the aerospace, defence and wind blade segments is concentrated at a smaller number of large facilities than is sometimes assumed. The list below is not exhaustive but covers most of the global capacity in each segment.
Aerospace primary structure
Boeing Everett WA and Charleston SC build the 787 and other commercial twin-aisle programmes. Airbus Hamburg, Toulouse and an Airbus Asian assembly facility build the A350 and A330 programmes. Spirit AeroSystems Wichita is a major tier-one supplier of fuselage and wing structure. GKN Aerospace operates composite manufacturing plants in the US, UK and the Netherlands. Mitsubishi Heavy Industries, Kawasaki Heavy Industries and Subaru Aerospace build composite primary structure for the 787 fuselage barrels under long-term partnership agreements. Tier-one composite suppliers including Kratos, Leonardo, ITP Aero and Saab carry significant programme content.
Wind blade
Vestas operates wind blade factories worldwide, with regional manufacturing hubs in Europe, North America and Asia, plus the announced Burnie Tasmania facility. Siemens Gamesa Cuxhaven Germany and Hull UK are the two largest single offshore wind blade factories in Europe. GE Onshore and Offshore (LM Wind Power) operates blade factories in multiple regions. Goldwind, Envision, Mingyang and other Asian wind OEMs operate large blade manufacturing capacity. Nordex Rostock is a major German wind blade producer. TPI Composites is an independent blade manufacturer producing for multiple OEMs.
Defence aerospace
Lockheed Martin Aeronautics Fort Worth Texas is the F-35 final assembly site, with composite structure from Northrop Grumman and partner suppliers across the F-35 Global Sustainment programme. Boeing Defense, Space and Security operates composite capacity for the F-15EX, F/A-18 Super Hornet and KC-46 programmes. BAE Systems composite capacity in the US, UK and Australia supports the Eurofighter Typhoon, Tempest, F-35 partner work and Australian Defence Force programmes.
Australian composite manufacturing
Quickstep Holdings (Bankstown New South Wales and Geelong Victoria) is the largest dedicated independent composite manufacturer in Australia. Boeing Aerostructures Australia (Port Melbourne and Fishermans Bend) builds composite structure for the 787, 737 and 777 programmes and has been one of the longest-running composite manufacturing operations in the country. Marand Precision Engineering supports F-35 composite structure work. BAE Systems Australia composite capacity supports defence platforms across air, land and sea. Lovitt Technologies operates composite and metal aerospace manufacturing. CSIRO Manufacturing carries out R&D and demonstration-scale composite manufacturing for aerospace, defence and renewable energy applications.
The AUKUS Optimal Pathway is driving multiple new composite manufacturing capacity announcements at Henderson WA and Adelaide SA. The Hunter-class frigate programme at Osborne South Australia carries significant composite content. The Vestas wind blade factory at Burnie Tasmania is the first major dedicated wind blade facility in Australia, with additional wind turbine OEM facility evaluations under way for the Bass Strait, Illawarra, Hunter and Gippsland offshore wind programmes.
AUKUS and the new Australian composite manufacturing capacity
The AUKUS Optimal Pathway announced by the Australian, UK and US governments in March 2023 is reshaping the Australian defence industrial base. The headline commitment is a Virginia-class boat from the early 2030s and the SSN-AUKUS class through a Henderson WA and Adelaide SA shipbuilding base, with first SSN-AUKUS launch in the early 2040s. The composite content on a single nuclear-powered submarine is hundreds of tonnes of structural and acoustic material, including sonar dome housings, propulsion train fairings, internal compartmentation, machinery raft fairings, ballistic panels and pressure hull testing articles.
The programme is driving multiple new composite manufacturing facility announcements at Australian sites — both at the prime contractor level and across the tier-one and tier-two supply chain. The Australian Submarine Agency, the Royal Australian Navy, BAE Systems Australia, ASC Pty Ltd, Babcock Australasia, Civmec and the broader sovereign industrial capability network are coordinating the build-out. Each new facility requires composite-specific HVAC including ISO 8 lay-up rooms, autoclave and OOA cure oven HVAC, VOC and styrene capture, and carbon fibre and aramid dust extraction.
SBKJ supplies the rectangular and spiral ductwork forming machinery used to fabricate the HVAC ducting at AUKUS-supporting facilities — both at the facility build-out phase by Australian fabrication shops, and at the operating phase for plant expansion ductwork. The combination of an SBAL-V auto duct production line for general supply and clean room ductwork, an SBTF spiral tubeformer for autoclave room exhaust and dust extraction return air, and a TDF flange former for low-leakage clean room connections is the standard SBKJ specification for this duty.
Wind blade Australia and the offshore wind programme
The Commonwealth Renewable Energy Zone programme and the offshore wind targets in Bass Strait, Illawarra, Hunter and Gippsland are driving evaluation of additional Australian wind blade manufacturing capacity. Vestas has announced a wind blade factory at Burnie Tasmania to support the domestic onshore market and to provide an Australasian source for offshore wind installations across the Pacific.
Wind blade factories are dominated by infusion lay-up of GFRP shell halves with carbon spar caps. The HVAC specification is dominated by VOC and styrene capture at the open mould bays and at the gel coat application station. A typical wind blade factory has 4–8 mould bays, each 60–120 metres long, with dedicated VOC capture along the length of each mould. The fabrication shop ducting requirement is significant — every blade factory has miles of HVAC duct in supply, return, exhaust and dust extraction service.
SBKJ duct fabrication machinery for composite manufacturing
SBKJ Group manufactures three machine families that cover the duct fabrication requirements of a typical composite manufacturing facility.
SBAL-V Auto Duct Production Line. The SBAL-V coil-fed line forms rectangular galvanised duct from coil through cut-to-length, corner notching, longitudinal seaming and TDF flange forming in one pass. Throughput is typically 8–15 metres per minute on standard galvanised G90, with reduced throughput on stainless steel coil and on heavy-gauge applications. The SBAL-V is the workhorse for general supply and return ductwork across all composite plant zones outside the chemical and high-temperature exhaust ducts. Read the SBAL-V technical specification.
SBTF Spiral Tubeformer. The SBTF produces round spiral duct from coil at high throughput. Composite plant applications include autoclave hall exhaust, dust extraction return air on trim and finishing booths, OOA cure oven exhaust on the cooler downstream sections, and general process exhaust runs. The SBTF handles galvanised, 304L stainless and aluminium coil with appropriate forming tooling. Read the SBTF technical specification.
TDF Flange Former. The TDF flange former produces the low-leakage TDF flange profile required at every rectangular duct connection in low-leakage service. Composite plant applications include lay-up clean room supply and return ducts, tooling room ducts, and any other zone where Sealing Class A or B is required per AS/NZS 4254 or SMACNA equivalent. The TDF flange former integrates with the SBAL-V production line and is also available as a standalone machine for retrofit applications. Read the TDF technical specification.
For composite manufacturing facilities serving aerospace, AUKUS and other defence programmes, SBKJ supplies the machinery in 380V/50Hz Australian configuration with English-language documentation, local-language support from the Box Hill North Victoria office, and full ISO 9001 and CE certification. Lead time from purchase order to Factory Acceptance Test is typically 90–120 days on a complete line, with installation and commissioning by SBKJ engineers at the customer's Australian facility.
Construction and commissioning
Composite plant HVAC commissioning is more demanding than standard commercial HVAC commissioning because the compliance burden is higher and the process tolerance bands are tighter. A complete commissioning programme covers seven domains.
Capture velocity verification at every source-capture hood. Hot-wire anemometer measurement at the hood face under actual operating conditions, compared against the design capture velocity from the ACGIH IV Manual. Failure to meet design capture velocity requires hood rework, fan resizing or duct rebalancing.
Dust load testing under simulated machining throughput. Dust collector duty cycle confirmation at the design throughput of cured CFRP, GFRP or aramid removed per shift. HEPA filter integrity testing per the relevant standard before handover.
Autoclave thermal mapping. Temperature distribution survey across the autoclave hall during a representative cure cycle, with measurement at operator working positions, control electronics positions and the autoclave external surface. Confirms the HVAC removes heat fast enough to keep the working positions below 28°C dry bulb.
Lay-up clean room ISO 14644 particle count. Particle count survey under operational conditions per ISO 14644-1, with documentation of the cleanliness class achieved. Confirmation of pre-preg out-life conditions including temperature and humidity stability over a 24-hour period.
Pressure cascade verification. Differential pressure measurement at every doorway and pass-through between zones, confirming the design pressure cascade — lay-up positive, trim and finishing negative, autoclave hall neutral or slightly negative, VOC and styrene exhaust zones negative.
Gasket and sealant material confirmation. Visual inspection at duct connections in chemical service, with material certificate verification. EPDM or PTFE gaskets in styrene exhaust service, butyl in general HVAC, and silicone-free in any aerospace primary structure clean room.
24-hour stability run. Continuous data logging of temperature, humidity, pressure cascade and capture velocity over a 24-hour period under representative production load. Out-of-band events trigger HVAC rework before handover.
How SBKJ supports composite manufacturing customers
SBKJ Group has supplied HVAC duct fabrication machinery to composite manufacturing facilities across the global supply chain — aerospace tier-one suppliers, wind blade factories, defence prime contractors and the broader composite industrial base. Our composite plant customers typically use a combination of the SBAL-V auto duct production line, the SBTF spiral tubeformer and the TDF flange former, configured for the specific duct material mix at the customer's facility.
- Materials capability — galvanised G90, 304L stainless steel and aluminium coil on the SBAL-V and SBTF, with the appropriate forming tooling for each material. Clean room HVAC duct machinery overview.
- Australian sales and engineering — Box Hill North Victoria office covers all Australian customers from initial RFQ through installation, commissioning and after-sales. SBKJ Australia overview.
- Lead time — 90–120 days from purchase order to Factory Acceptance Test on a complete duct line, plus 35–45 days ocean freight to Melbourne, Sydney, Adelaide, Fremantle or Brisbane.
- Installation and commissioning — 1–2 SBKJ engineers on site for 5–10 days for installation, mechanical commissioning and electrical commissioning, with operator and maintenance training included.
- After-sales — one-year wear-parts kit shipped with the machine, 72-hour remote support response, 10-year+ parts continuity guarantee, English-language service from the Australian office.
Get an SBKJ quote for composite plant HVAC duct machinery →
FAQ
What VOC and styrene exposure limits apply to composite manufacturing HVAC design?
Three reference points sit on every composite plant HVAC design brief. OSHA 29 CFR 1910.1000 sets a styrene 8-hour TWA of 100 ppm and a 200 ppm ceiling. NIOSH REL is 50 ppm 8-hour TWA. ACGIH TLV is 20 ppm 8-hour TWA — the strictest of the three and the de facto international design target. Open-mould lay-up shops typically design ductwork to capture at the source so the lay-up worker breathing zone stays under 20 ppm even when local exhaust ventilation is at 80 percent of nameplate. AS 1668.2 sets the Australian general dilution ventilation framework but does not replace ACGIH-derived capture velocities.
How is carbon fibre machining dust handled in HVAC ductwork?
Carbon fibre machining dust from trim, drill and grinding operations on cured CFRP is conductive, abrasive and a respiratory plus skin irritant. Three rules apply. First, source capture at the machining tool with hood face velocity sized per ACGIH Industrial Ventilation Manual chapter on plastics manufacturing. Second, HEPA filtration H13 or H14 mandatory before any return air recirculation. Third, the dust collector and downstream ductwork must be evaluated against BS EN 16275 and NFPA 484-style combustible dust analysis — bare dry carbon fibre dust is not strongly combustible but mixed dusts in finishing shops can be. Antistatic-treated galvanised duct or 304L stainless is the standard wetted-side specification.
What temperature and humidity must a composite lay-up clean room hold?
Pre-preg lay-up rooms typically run 18–22°C and 40–65% RH, with ISO 14644 Class 8 cleanliness or better. Temperature stability protects pre-preg out-life — most aerospace pre-preg systems are qualified for 30 days out of freezer at 21°C and lose qualified out-life rapidly above 24°C. Humidity above 65% can be absorbed into resin and degrade interlaminar shear, while humidity below 30% causes static problems on dry carbon fabric handling. HVAC ducts feeding the lay-up room are typically 304L stainless with low-velocity diffusers to keep air movement below 0.25 m/s at the lay-up surface so dust is not stirred up off the bench.
How much HVAC capacity does an autoclave room need?
Autoclave rooms have two distinct loads. The autoclave external surface radiates significant heat during the cure cycle even with lagging — typical figure is 8–15 kW thermal load per cubic metre of autoclave volume during the heat-up phase. The control electronics cabinet for the autoclave needs its own conditioned space at 18–24°C. Plan a dedicated exhaust hood above the autoclave door for the loading-bay vapour release at door opening, plus general dilution ventilation at 6–10 air changes per hour. Out-of-autoclave (OOA) cure ovens require NFPA 86 compliance for heated process equipment exhaust.
What duct materials should I specify for a composite manufacturing facility?
Five material zones cover most composite plants. (1) General supply and return — galvanised G90 to AS/NZS 4254 or SMACNA. (2) Lay-up clean room and tooling room — 304L stainless internally polished or epoxy-coated galvanised. (3) Open-mould VOC and styrene exhaust — fibreglass-reinforced plastic (FRP) or polypropylene-lined steel for chemical resistance. (4) Carbon fibre dust extraction — antistatic-treated galvanised or 304L stainless with bonded grounding for static dissipation. (5) Autoclave loading bay exhaust — 304L stainless rated for the temperature spike at door opening. Specifying the wrong material is the most common rework item we see at commissioning.
How does the AUKUS submarine programme affect Australian composite manufacturing capacity?
The AUKUS Optimal Pathway announced in March 2023 commits Australia to building Virginia-class boats and the SSN-AUKUS class through a Henderson WA and Adelaide SA shipbuilding base. Composite content on modern submarines includes sonar dome housings, propulsion train fairings, internal compartmentation and pressure hull testing articles. The programme is driving new composite manufacturing capacity announcements at multiple Australian sites. Each new facility requires composite-specific HVAC including ISO 8 lay-up rooms, autoclave and OOA oven HVAC, VOC capture and carbon fibre dust extraction. SBKJ supplies the rectangular and spiral ductwork forming machinery used to build that ducting on site or in Australian fabrication shops.
What HVAC duct fabrication machinery is best for composite plant ducting?
Three SBKJ machines cover most composite plant duct production. The SBAL-V auto duct production line forms the rectangular galvanised supply and return ductwork for general HVAC and clean room supply at high throughput. The SBTF spiral tubeformer produces the round duct used for autoclave room exhaust, trim and finishing dust extraction return air, and general process exhaust runs. The TDF flange former produces the tight TDF connections required for low-leakage clean room ductwork in pre-preg lay-up areas. For 304L stainless duct in clean room and tooling room zones, the SBAL-V handles stainless coil with adjusted forming tooling, and stainless TDF flange is formed on the same TDF line with the appropriate roller set.
What is the typical lead time for HVAC duct machinery for an Australian composite manufacturing facility?
For an SBKJ auto duct production line plus spiral tubeformer plus TDF flange former configuration sized for a mid-size composite plant, plan 90–120 days from purchase order to Factory Acceptance Test, plus 35–45 days ocean freight to Melbourne, Sydney, Adelaide, Fremantle or Brisbane, plus 2–3 weeks for installation and commissioning by SBKJ engineers. Total project timeline from PO to first production duct is typically 6–8 months. AUKUS-related projects with security-cleared personnel requirements should add 4–8 weeks for clearance processing. SBKJ has Australian sales and engineering at the Box Hill North Victoria office.
