Why emergency services ductwork is its own design discipline
An emergency services facility is not a commercial office and is not a hospital, although it shares some of each. A modern Australian police station, fire station, ambulance base or SES headquarters is, in practical engineering terms, a small high-mix building that has to simultaneously satisfy: a 24/7 communications centre that cannot lose cooling, a heavy-vehicle appliance bay loaded with diesel exhaust and contaminant runoff, secure custody zones built to AS 4072.1 Class C construction, an SCBA and bunker gear decontamination wash, an evidence store with DNA preservation conditions, a firearms vault, interview rooms with broadcast-grade acoustic targets and a station mess with normal-office air. Each of these is a different ASHRAE Applications Handbook Chapter 9 sub-occupancy, each has its own pressure-cascade requirement, and almost none of them can be safely combined into a single return-air path. The price of getting that wrong shows up as cross-contamination, evidence loss, broken radio dispatch and, in the worst case, occupational health incidents inside the apparatus bay.
The guide below is written for the people who actually scope, design, build and maintain these facilities in Australia. It is calibrated to the published agency design standards used by Fire and Rescue NSW, Fire Rescue Victoria, Queensland Fire and Emergency Services, the Department of Fire and Emergency Services WA, the South Australian Country Fire Service and Metropolitan Fire Service, the Tasmania Fire Service, the NSW Rural Fire Service, Ambulance Victoria, NSW Ambulance, Queensland Ambulance Service, SA Ambulance Service, St John Ambulance WA, Ambulance Tasmania, the NSW Police Force, Victoria Police, Queensland Police Service, the WA Police Force, South Australia Police (SAPOL), Tasmania Police, Northern Territory Police, ACT Policing, the Australian Federal Police (AFP), Australian Border Force (ABF), the Australian Security Intelligence Organisation (ASIO), the Australian Secret Intelligence Service (ASIS), the Australian Signals Directorate (ASD), the Australian Criminal Intelligence Commission (ACIC), AUSTRAC and every state SES — NSW SES, VICSES, Queensland SES, SA SES, WA SES, TAS SES, ACT SES and NT SES. The base codes are common across all of them; the overlays differ.
The base code stack
Every Australian emergency services project sits on the same base stack of codes, regardless of which agency is the eventual occupier. Understanding the stack is the first move any design engineer makes after receiving the brief.
The ASHRAE Applications Handbook Chapter 9 (Health Care and Institutional Facilities) is the international engineering reference for institutional ventilation, and most state agency standards quote it directly for any care, custody or control space inside the building. Chapter 9 governs the temperature, humidity, filtration and pressure cascade defaults that flow down into custody cells, secure interview rooms, decontamination, evidence and the staff change rooms attached to the apparatus bay. Where ASHRAE Chapter 9 is more conservative than the local code, the Chapter 9 figure usually wins on a state agency brief.
The mandatory Australian ventilation code is AS 1668.2, which sets the outside-air baseline for every conditioned space in the building. The headline numbers — 10 L/s per person for general office space, 25 L/s per WC pan or urinal for sanitary areas, with special-case rates for kitchens, laundries, plant rooms and high-occupancy spaces — are the figures that appear on every mechanical schedule sheet. AS 1668.2 also defines the minimum exhaust requirements for special bays such as workshops, battery rooms and chemical stores, all of which routinely appear inside emergency services facilities.
AS 4072.1 covers fire-resistant penetration sealing and is the standard agencies reference when they want secure, Class C high-integrity construction around custody cells, evidence stores and weapons containment. In ductwork terms, AS 4072.1 Class C means sealed-seam Class A or Class B air-tightness, 1.2 mm to 1.6 mm gauge steel, anti-contraband welded mesh on every cell-side register, and tamper-resistant fixings on every access panel inside the cell perimeter.
The NFPA 1500 Standard on Fire Department Occupational Safety, Health and Wellness Program is the dominant international document for firefighter occupational health, and every Australian fire service either references it directly or operates a state-equivalent program modelled on its core requirements. NFPA 1500 is the document behind apparatus-bay vehicle exhaust capture mandates, the diesel particulate exposure limits inside fire stations, and the bunker-gear separation rules that have become standard practice in every new Australian fire station built since roughly 2015.
AS 1851 governs the routine inspection, testing and maintenance of fire protection equipment in service — including every fire damper, smoke damper and motorised damper in the ductwork. AS 1851 is not a design code, but it controls the ongoing maintainability of every penetration in the system, which means access panels and witnessing points have to be designed into the duct route from day one.
Two further references appear on most agency briefs. AFAC (Australasian Fire and Emergency Service Authorities Council) publishes inter-agency design notes that flow into most fire and SES projects. AS/NZS 2243.3 and the OGTR requirements for any PC2 forensic biology containment space supersede the general ASHRAE Chapter 9 defaults where they conflict — relevant on any police station with an in-house forensic services unit.
How a station gets zoned
Before any duct sizing happens, the designer divides the building into compatible HVAC zones and locks the secure perimeter. The zoning logic is consistent across all agencies.
The public foyer and counter is a normal commercial office zone at AS 1668.2 baseline rates, with the counter sitting on a slight positive cascade (5 to 10 Pa) so a sneeze across the counter does not drive contaminated air into the operational area. The operational office area behind it is a standard office zone — NC-40, 22 to 24 °C, 40 to 60% RH.
The secure interview rooms diverge first — acoustically isolated to NC-30 with attenuated supply and return so no audible HVAC noise lands on the recording. Most agencies prohibit in-room return grilles; transfer ducts with attenuators carry return air to a corridor pickup.
The custody cells, watch-house and detainee anteroom are the most regulated HVAC zones in the building — AS 4072.1 Class C perimeter, sealed-seam Class A or B duct, +5 Pa / −5 Pa cascade. The evidence store sits at 18 to 22 °C and 50 to 60% RH with HEPA on supply where biological evidence is stored. The firearms store is normal office-grade — security is handled by locksmiths, not HVAC.
The communications centre runs independent redundant cooling on its own duct. The fire appliance bay handles diesel exhaust at source and is the largest single ventilation load. The decontamination room sits adjacent on its own one-way exhaust. The bunker gear storage sits clean-side of decontamination on dehumidified duct. The hose drying tower is an isolated wet-air load. The kitchen and mess are normal canteen ventilation with AS 1668.2 kitchen exhaust on the cooking line.
The apparatus bay — diesel exhaust capture, air change rate and CO control
The single largest HVAC engineering decision on any fire station, ambulance station or large-vehicle SES facility is how the apparatus bay handles diesel exhaust at source. The science is unambiguous: a heavy-diesel fire appliance starting cold inside an enclosed bay generates a transient exhaust load in the order of one to two cubic metres per second of high-particulate, high-CO, high-NO2 air, almost all of it in the first 30 seconds before any general-ventilation dilution can respond. That short transient peak is what makes diesel exhaust the defining occupational exposure problem in modern firefighting, and it is the reason NFPA 1500 makes vehicle exhaust capture a near-mandatory requirement in any new fire station in the Western world.
The Australian engineering response has two layers. The first layer is general ventilation sized to give the bay 6 to 10 air changes per hour at supply, depending on the bay volume and the number of appliances. The second layer is source capture on each appliance — a flexible exhaust hose or magnetic snout that clips directly onto the tailpipe, captures the exhaust before it enters the bay air and discharges through dedicated ductwork to a roof termination. The two layers work together: the source capture handles the transient peak, the general ventilation handles the residual and the bay-air-quality monitoring confirms both are working.
The dominant source-capture technologies in Australian fire stations are Plymovent (Dutch origin, dominant globally) and Magnet-Schultz (German). Both offer magnetic or pneumatic tailpipe attachments that auto-release as the appliance leaves the bay, with a Plymovent-style trolley track running the length of the bay so the captured exhaust hose follows the appliance until departure. The captured exhaust then runs through galvanised or stainless ductwork to a roof termination, with a high-temperature flexible coupling between the hose and the hard duct to absorb the heat shock.
The carbon monoxide occupational exposure limit under Safe Work Australia is 30 mg/m³ as an 8-hour time-weighted average, which is equivalent to roughly 25 to 26 ppm. Apparatus-bay air quality monitoring is universally specified to alarm well below that — typical alarm setpoints are 25 ppm CO continuous, with a high-rate purge fan triggered at 35 ppm and an evacuation alarm at 50 ppm. NO2 is monitored to a 1 ppm 8-hour TWA. Diesel particulate matter, although harder to monitor in real time, is the headline carcinogen risk and is the reason source capture is preferred over high-rate dilution.
The supply and return ductwork for the bay itself is straightforward galvanised steel, sealed Class A, sized at the bay air change rate. The source-capture ductwork is the engineering-critical run — it has to handle exhaust gas at up to 350 °C from a hot appliance, with thermal expansion accommodated by sliding sleeves and the duct supports designed for thermal cycling. Most modern designs run the source-capture exhaust in 1.6 mm galvanised duct with stainless transitions at the appliance end, terminating on the roof through a weatherproof penetration with a thermal break to the roof structure.
One detail that is regularly missed by inexperienced designers: the apparatus-bay supply air should be heated to maintain at least 12 °C inside the bay through winter, but never recirculated. The bay air is single-pass — supply enters, mixes, and the entire bay volume leaves either through source capture during a callout or through general exhaust the rest of the time. Recirculating apparatus bay air through any office or accommodation zone is a categorical breach of NFPA 1500 and every state agency standard that flows from it.
The hose drying tower
A hose drying tower is a small, tall, hot, very wet room that exists to dry fire hoses after use. In a typical Australian metropolitan fire station the tower is 8 to 12 metres tall, 2 to 4 metres on plan, and contains a moving rack that suspends 30 to 60 metres of wet fire hose in long vertical drops. After a callout, those hoses can collectively dump 30 to 80 litres of water into the tower air over a 24 to 36 hour drying cycle.
The engineering challenge is dehumidification, not ventilation. A tower designed on AS 1668.2 ventilation rates alone will run at 90 to 100% RH for hours after a callout, which mildews the hoses and rots the tower itself. The correct design is a dedicated dehumidifier — usually a desiccant or refrigerant rotary unit — sized for the peak moisture load of the largest expected callout, with a small base airflow for makeup. Most modern stations target 35 to 45% RH inside the tower with the dehumidifier running, supplemented by heater coils at the supply to lift the air temperature and accelerate the drying.
Ductwork in the tower is short — typically a single supply diffuser at the top of the tower and a single return at the bottom — but it is exposed to high humidity and the occasional water spray, so 304 stainless duct is preferred over galvanised. The tower must be on its own ductwork loop with no air path back to any other room in the station.
Bunker gear storage and PPE rooms
The bunker gear storage room is a more demanding HVAC space than most non-fire designers realise. Modern bunker gear is a multi-layer aramid and PTFE composite — Nomex or PBI outer shell, Crosstech moisture barrier, aramid thermal liner — and each layer degrades on a defined humidity, temperature and UV curve.
NFPA 1851 and AFAC's Australian-aligned guidance both call for bunker gear stored at 18 to 22 °C, 50 to 55% RH, with zero direct sunlight and dedicated air movement to prevent moisture pockets. The room runs a small dedicated AHU with dehumidification, low-velocity supply, and gentle distribution — no high-velocity jets directly onto stored gear.
The room sits clean-side of the decontamination workflow on a one-way air path. Bunker gear storage sits at +5 Pa, the corridor at +5 Pa relative to decontamination, decontamination at −5 Pa relative to the apparatus bay. Wet PPE goes to decontamination first and only returns to bunker gear storage once cleaned and re-certified.
Decontamination room — SCBA and bunker gear wash
The decontamination room is where contaminated bunker gear and Self-Contained Breathing Apparatus (SCBA) are cleaned after a callout, particularly after structure fires that produce known carcinogens in smoke. This room sits between the apparatus bay and the bunker gear storage room in the workflow, and is the most chemically aggressive HVAC environment in the station.
The room has its own exhaust path discharging to a dedicated roof termination, with the ductwork in 304 stainless to handle the chlorinated disinfectants used in SCBA cleaning. The supply path is dedicated, with HEPA filtration on supply where biological contamination is suspected from any incident attended. The room runs at −5 Pa relative to the corridor, which guarantees that any vaporised disinfectant or particulate aerosol from PPE washing flows out the dedicated exhaust path rather than into the surrounding building.
Air change rate in the decontamination room is typically 12 to 15 ACH continuous, rising to 20 ACH during active washing through a station-officer-controlled high-rate boost. The boost runs for the duration of the wash cycle plus a 15 minute purge tail, then returns to the steady-state rate.
Custody cells, watch-house and the AS 4072.1 Class C secure construction perimeter
Police custody cells inside Australian police stations and watch-houses are built to AS 4072.1 Class C secure construction, which is the most stringent ductwork construction class on any non-defence facility in the country. The HVAC requirements run alongside the structural and security requirements, and every aspect of the ductwork is shaped by the security brief.
The base requirement is that nothing crosses the secure perimeter except through a controlled, inspectable opening. For ductwork, that means every supply and return register on the cell side of the perimeter sits behind a welded anti-contraband mesh — typically a 96 mm clear opening with stainless or hardened-steel mesh sized to prevent small contraband from being passed through the grille. The mesh is welded into a steel frame, the frame is bolted into the cell wall with tamper-resistant fixings, and the registers themselves use tamper-resistant security screws.
Inside the cell, the ductwork runs at 1.2 to 1.6 mm gauge galvanised or stainless steel, sealed Class A air-tightness to prevent any covert audio path through the duct. Every access panel inside the secure perimeter is a problem — the security designers prefer no access panels at all in the cell zone, which means duct routing has to avoid any need for in-cell maintenance access. Access panels for fire damper inspection and routine cleaning are placed entirely outside the secure perimeter, with the duct sized and routed to allow lawful AS 1851 inspection from the corridor side only.
The pressure cascade between the cell, the anteroom and the corridor is locked at +5 Pa to −5 Pa, with the cell typically sitting at −5 Pa, the anteroom at 0 Pa and the corridor at +5 Pa. The cascade does two things: prevents cross-contamination if a detainee is unwell, and prevents any odour or audible exchange from the cell into the wider station. Cell air is single-pass — supply enters, mixes, and the entire volume leaves through a dedicated cell exhaust path that discharges to a roof termination separate from every other exhaust point in the building.
Air change rate in cells is typically 6 to 8 ACH, with the supply distribution arranged so that the supply jet does not impinge directly on the bed or the toilet — both for detainee comfort and to prevent the supply diffuser becoming an anchor point for an attempted self-harm event. Most designs use a perimeter supply with a high return, the return grille positioned out of arm's reach in the upper third of the wall.
Interview rooms attached to the watch-house are not Class C, but they carry the NC-30 acoustic requirement so that no audible HVAC noise lands on the recording — supply and return are transferred via attenuated ducts that step down to NC-30 at the room face, with no in-room return grille.
The watch-house corridor itself sits as the buffer between the cells and the wider station. Pressure cascade is positive into the corridor, return air picks up at the corridor and recirculates through the watch-house AHU. Any incident that requires full lockdown — typically a suspected airborne biological exposure or a cell-related event — triggers a switch to 100% outside air on the watch-house AHU, with all return-air recirculation closed off until the station officer signs off the all-clear.
Evidence storage and DNA preservation
Modern police evidence rooms are conditioned for DNA preservation. Biological evidence — blood, hair, tissue — degrades on a humidity and temperature curve, and the Australasian DNA Advisory Group's published guidance aligns Australian agency standards on a single conditioned-storage band: 18 to 22 °C dry bulb, 50 to 60% RH, low UV exposure, low air-velocity disturbance. The mechanical brief that flows from that is a small dedicated AHU with dehumidification, sized for the room and capable of holding that band 24 hours a day, 365 days a year.
Air change rate in evidence storage is intentionally low — typically 2 to 4 ACH, which is enough to prevent stagnation but low enough to avoid disturbing tagged samples on the racks. Supply distribution uses low-velocity diffusers in the upper plenum, with low-velocity return picking up at the opposite end of the room. Filtration is typically MERV 13 or higher on supply, and HEPA on supply where the agency standard requires it for biological evidence.
The room sits on a small positive cascade relative to the surrounding corridor — typically +5 Pa — so that nothing from the corridor infiltrates the evidence room. The exhaust path is a dedicated stub that discharges through a small filter to the outside, rather than recirculating back through the AHU.
Firearms store
The firearms store inside a typical Australian police station is, surprisingly to non-specialists, a normal office-grade HVAC zone. The security brief is handled by the locksmiths, the safe builders and the steel-cage perimeter — not by the mechanical engineer. The mechanical brief is simply to keep the room at ambient temperature and humidity, with normal AS 1668.2 ventilation rates. Some agency standards prefer that the firearms store sits on a small positive cascade to prevent humid air infiltration during the wet season, which is the only HVAC-specific overlay.
The exception is any firearms store that doubles as an ammunition store. Smokeless powder is humidity-sensitive, and any large ammunition holding will carry its own conditioned-storage brief — typically 21 °C dry bulb and 50% RH, mirroring the evidence store conditions.
Forensic services — PC2 containment where present
Police stations that include an in-house forensic services unit have a small PC2 (Physical Containment Level 2) wet-lab on site, typically for initial sample triage rather than full forensic analysis. PC2 containment is defined by AS/NZS 2243.3 and the OGTR, and it pulls the lab onto a dedicated AHU with HEPA exhaust and a strict negative cascade — usually −15 Pa relative to the corridor.
PC2 ductwork is 304 stainless on exhaust, with the exhaust path discharging through HEPA filtration to a roof termination at least 3 metres above the roof line and at least 7.5 metres from any air intake or operable window. The exhaust fan is sized to maintain negative pressure under all building operating conditions, including a fully open lab door, and is duty/standby with automatic changeover on fan failure.
The supply path to the PC2 lab is typically MERV 14 filtered with no recirculation — single-pass air with full outside-air supply, balanced against the HEPA exhaust to maintain the negative cascade. The supply ductwork can be galvanised, since the supply air is clean — the stainless requirement applies to the contaminated exhaust path.
The communications centre — 000 dispatch, VKG and police state operations
Every state operates one or more 24/7 communications centres that handle 000 dispatch, fire turnout, ambulance dispatch and police radio. These centres are the single highest-availability rooms in the entire emergency services portfolio, and they are designed accordingly — N+1 cooling minimum, N+2 in major-capital-city centres, redundant chilled-water risers, dual UPS-fed CRAC units, and zero single point of failure on the air path.
The standard mechanical brief is 22 to 24 °C dry bulb, 40 to 55% RH, NC-30 acoustic at the operator console and 24/7/365 availability with no scheduled downtime. The cooling load is dominated by the dispatch consoles themselves — each operator position is roughly 800 W to 1.5 kW of IT load, and a typical metropolitan 000 dispatch centre runs 20 to 40 operator positions, plus a separate set of supervisor consoles, plus the network and radio infrastructure rooms behind the operations floor.
The ductwork on the operations floor is sealed-seam Class A, internally lined where the acoustic target requires, with sized supply diffusers chosen for low NC throw — typically high-volume, low-velocity perforated diffusers at the ceiling plane. Return air is picked up at floor level beneath the consoles, transferred through a sub-floor plenum back to the CRACs, with the sub-floor plenum itself sealed and pressurised to manage the supply path.
The N+1 redundancy is implemented at every level. Two chilled-water risers serve the room, each capable of carrying the full load alone, with automatic changeover on chiller failure. Two CRAC units are in service with a third on standby, configured so that the loss of any single unit triggers no operational impact. Two UPS strings feed the CRAC controls and the dispatch consoles, with automatic failover.
The operations command centre — typically attached to the communications centre but distinct from it — sits on a slightly relaxed brief: 22 to 24 °C, NC-35, N+1 cooling, full UPS backing. The command centre is where incident commanders convene during major events, and is sized for occasional surge occupancy rather than continuous 24/7 staffing.
Ambulance bases and SES headquarters
Ambulance bases share the apparatus-bay design problem with fire stations but at a smaller scale. A typical Ambulance Victoria, NSW Ambulance, Queensland Ambulance Service, SA Ambulance Service, St John Ambulance WA or Ambulance Tasmania base has one to four ambulance bays, each handling a single light-diesel vehicle with substantially lower exhaust output than a heavy fire appliance. The same source-capture engineering applies — Plymovent-style tailpipe capture, dedicated stainless exhaust ductwork, roof termination — but the duct sizing is roughly half that of a fire station.
Ambulance bases add one specific clean-side requirement: the patient transfer bay between the ambulance bay and the station interior, where stretcher cases are transferred between the ambulance and any in-station clinical assessment area. That transfer bay sits on a slight positive cascade relative to the ambulance bay to prevent diesel exhaust ingress, and is typically conditioned to hospital-equivalent comfort to make patient handovers comfortable in extreme weather.
SES (State Emergency Service) headquarters facilities — NSW SES, VICSES, Queensland SES, SA SES, WA SES, TAS SES, ACT SES and NT SES — have the broadest mix of any emergency services facility. A typical SES regional headquarters includes a vehicle bay for medium-rescue trucks and boat trailers, a flood-rescue equipment store, a chainsaw and tool workshop, an operations room, a volunteer training room and the usual office and mess accommodation. The vehicle bay handles diesel exhaust to the same standard as a fire appliance bay, scaled for the smaller fleet, and the workshop carries its own dust and fume extraction load that is independent of the general ventilation.
Volunteer fire services — CFA, NSW RFS and rural brigades
The Australian volunteer fire services — the Country Fire Authority in Victoria, the NSW Rural Fire Service, the volunteer arm of Queensland Fire and Emergency Services, the Department of Fire and Emergency Services WA volunteer brigades, the SA Country Fire Service volunteer units, the Tasmania Fire Service volunteer arm and equivalent volunteer organisations in NT and ACT — operate the largest single fleet of fire stations in the country. The NSW Rural Fire Service alone supports more than 2,000 brigade locations, the CFA supports a similar number of Victorian volunteer brigades.
The HVAC brief on a volunteer brigade station is simpler than a full-time metropolitan station, but the apparatus-bay diesel exhaust capture requirement still applies in every modern build. Most new volunteer brigade stations built in the past decade run a single-bay or two-bay configuration with Plymovent-style tailpipe capture on each bay, a small operations and training room, a mess and amenities, and minimal back-of-house. Custody cells and forensic facilities do not apply. Communications centres do not apply at brigade level — the dispatch is handled by the state communications centre, with brigade stations only carrying a radio room rather than a dispatch centre.
The volunteer station design is dominated by cost-per-square-metre rather than absolute availability, which pulls the mechanical brief towards simple AS 1668.2 baseline ventilation, packaged DX cooling for the office and training rooms, and a single dedicated exhaust path for the apparatus bay. The ductwork is conventional galvanised, sized to AS/NZS 4254, and built to standard SMACNA gauges.
State-by-state operator landscape
The Australian emergency services landscape is split between the federal agencies, the state police forces, the state fire services, the state ambulance services and the state SES. The operator-specific design standards differ in detail but converge on the same code stack above.
Police forces
The Australian Federal Police (AFP) operates the national-level law enforcement service, with major facilities in Canberra (national headquarters at Edmund Barton Building), Sydney, Brisbane and state liaison offices in every capital. AFP facilities include the most stringent secure construction zones of any police service in the country, and the AFP also operates the policing function for the Australian Capital Territory as ACT Policing, including the City station and the various district stations across Canberra.
The NSW Police Force operates more than 400 stations including the Police Headquarters at Parramatta, the Sydney Police Centre, the various regional command centres and the city and suburban stations. NSW Police custody facilities follow the AS 4072.1 Class C standard with the additional NSW Police Custody Manual overlay that governs cell HVAC.
The Victoria Police operates more than 200 stations including the Police Centre at Spencer Street Melbourne, the regional and district stations, and the specialist facilities such as the Crime Command. Victoria Police custody facilities also follow AS 4072.1 Class C with additional state agency overlays.
The Queensland Police Service runs 333 stations across the state, the WA Police Force runs 159 stations, South Australia Police (SAPOL) runs the Adelaide headquarters and roughly 70 stations, Tasmania Police runs the Hobart headquarters and roughly 50 stations, and the Northern Territory Police runs the Darwin headquarters and the regional stations.
The Australian Border Force (ABF) operates immigration detention and customs facilities at every major airport and seaport, with custody and detention zones built to the equivalent of AS 4072.1 Class C. AUSTRAC and the Australian Criminal Intelligence Commission (ACIC) operate intelligence and analysis facilities that are office-grade for the analyst space but include high-security communications and document-handling zones.
The intelligence agencies — the Australian Security Intelligence Organisation (ASIO), headquartered in the purpose-built Ben Chifley Building in Canberra, the Australian Secret Intelligence Service (ASIS), and the Australian Signals Directorate (ASD) — operate facilities with the most stringent secure construction requirements of any government building in the country, well beyond the AS 4072.1 Class C standard. These facilities are designed under a separate classified standard set, and the public guidance in this article does not apply to them. The mention here is for completeness of the operator landscape.
Fire and Rescue services
Fire and Rescue NSW operates more than 326 stations across NSW, headquartered at Greenacre in Sydney. Fire Rescue Victoria operates more than 80 stations across the Melbourne metropolitan area and major regional centres, following the 2020 merger of the Metropolitan Fire Brigade and the Country Fire Authority full-time stations into a single career service. The Country Fire Authority (CFA) continues as the volunteer arm in Victoria, operating well over 1,000 brigade locations across the state.
The Queensland Fire and Emergency Services (QFES) operates more than 280 urban stations plus a large rural and volunteer network. The Department of Fire and Emergency Services (DFES) WA operates the WA career fire service and the WA volunteer brigades. The South Australia Country Fire Service and the South Australia Metropolitan Fire Service together cover the SA fire response. The Tasmania Fire Service operates the Tasmania-wide network, and the NSW Rural Fire Service operates more than 2,000 brigades and is the largest volunteer fire service in the world by volunteer headcount.
Ambulance services
Ambulance Victoria, NSW Ambulance, Queensland Ambulance Service (QAS), SA Ambulance Service, St John Ambulance WA and Ambulance Tasmania operate the state ambulance fleets. Each runs a network of ambulance bases ranging from single-vehicle suburban bases through to large regional stations with 6 to 10 vehicle bays and supporting clinical assessment, training and accommodation space.
State Emergency Services
NSW SES, VICSES, Queensland SES, SA SES, WA SES, TAS SES, ACT SES and NT SES operate the storm, flood and general rescue response in each state, with a mix of paid headquarters staff and a large volunteer base. SES facilities include the regional headquarters at the capital city plus the brigade-style local units across the state.
Ductwork material selection by zone
The material selection across an emergency services facility is dominated by the zoning logic above. Galvanised steel handles the bulk of the work, with stainless reserved for the chemically aggressive or biologically contaminated paths.
Z275 galvanised steel to AS 1397 is the default for all general office, accommodation, training, foyer, mess, evidence-store supply, firearms store, communications centre supply, operations command, watch-house corridor and apparatus-bay general supply. The Z275 coating provides adequate corrosion resistance for typical Australian indoor air and the 30 year design life of the building.
304 stainless steel is specified for: SCBA decontamination room exhaust, custody cell wet exhaust where chemical cleaning chemicals are used, hose drying tower supply and exhaust, forensic PC2 exhaust, and the source-capture exhaust ductwork on diesel appliances where it crosses the thermal-shock band. Some agency standards also specify 304 stainless for the cell-face register and frame, because the chemical cleaning regime inside cells is aggressive.
1.2 to 1.6 mm gauge is the standard for AS 4072.1 Class C secure construction zones, regardless of whether the duct is galvanised or stainless. The thicker gauge resists tampering and gives the duct the rigidity to maintain the seal under forced entry attempt.
Polyurethane-foam composite ducting (PIR/PUR sandwich panel duct) is rarely used in emergency services projects. The fire-rating cascade, the secure construction zones and the heavy mechanical demands of apparatus bays and decontamination all push the specification to metal ductwork. Composite duct only appears occasionally in low-risk back-of-house areas where it offers an insulation cost saving over insulated galvanised.
Acoustic targets by zone
Acoustic performance is a defining brief item in emergency services design, because so much of the operational work is audio-dependent — radio dispatch, interview recording, command-and-control briefings, station alarm tones for callout. Each zone carries an explicit NC (Noise Criterion) target that flows into the ductwork sizing and the diffuser selection.
NC-25 in custody cells — the cells themselves are kept quiet enough that the detainee can sleep, which means low-velocity supply, attenuated branch ducts and oversized diffusers. NC-25 also discourages any covert audio path through the duct.
NC-30 in communications centre and interview rooms — the operator can hear the radio clearly without HVAC noise on the channel, and the interview recording captures the detainee's voice cleanly without an audible AHU hum on the audio track.
NC-35 in operations command centre — slightly more relaxed than the dispatch floor because the command centre is briefing-driven rather than continuous-listen.
NC-40 in general office, station mess, training rooms and the apparatus bay — standard commercial-office levels, no special attention needed beyond normal good practice on diffuser selection.
NC-45 in plant rooms and the workshop — the spaces are not occupied for long periods and standard plant-room acoustic targets apply.
24/7 operation, redundancy and resilience
The defining commercial feature of an emergency services facility is that it never closes. The station has to be operational on Christmas Day at 2 am with the same reliability as a Monday at 10 am.
Minimum redundancy for any operational space is N+1 — a small fire station might run two AHUs on the apparatus bay where one would carry the load; a metropolitan 000 dispatch centre runs three CRACs where two would suffice, plus redundant chilled-water risers, UPS strings and dual gensets. N+2 applies in the largest metropolitan communications centres and major operations command facilities where coincident failure has to be survivable.
On ductwork, the redundancy brief shows up as redundant return paths, cross-connected supply trunks where allowed, bypass dampers around critical filter banks, and isolation dampers at every zone boundary so a contamination event in one zone can be contained without taking down the rest of the building.
Fire compartmentation and AS 1851 maintainability
Every duct crossing a fire-rated wall in an emergency services facility carries a fire damper, a smoke damper or both, depending on the rating. Every one of those dampers has to be accessible for routine inspection under AS 1851, which means an access panel adjacent to each damper of sufficient size to allow visual inspection, manual operation and replacement of the damper sleeve if required.
The maintainability brief flows back into the duct routing during design. Every fire damper has to be reachable from a maintainable corridor or roof void without requiring entry into a secure space — no fire dampers buried inside cell perimeters with no lawful access, no dampers hidden behind permanent ceiling tiles, no dampers reachable only through a ladder run that violates safe working at heights. The agency client's facilities team carries the AS 1851 maintenance burden for the next 30 years, and they will reject any layout that traps a damper behind a sealed perimeter.
Smoke detection and stair pressurisation interfaces are also part of the AS 1851 picture. Every smoke detector in the duct feeds the building fire panel, every motorised damper has a feedback contact to the fire panel, and every stair pressurisation fan has a documented test point. The HVAC contractor signs off on the AS 1851 baseline at commissioning and hands a maintainable system to the client's contracted maintainer.
The pressure cascade map for a typical police-fire-ambulance complex
A consolidated police-fire-ambulance complex — increasingly common in regional Australia where the three services share a single site for cost reasons — runs the most complex pressure cascade of any single emergency services building. The cascade map looks like this in practice.
Most positive (+15 Pa or higher relative to outside): evidence storage, bunker gear storage and operations command centre. These rooms are protected from any infiltration from anywhere else in the building, which means the supply has to dominate the air balance and any spill goes outward through the corridor.
Mid-positive (+5 to +10 Pa): general office, communications centre, watch-house corridor, ambulance clinical assessment, interview rooms, foyer-side public counter.
Neutral (0 Pa): mess, kitchen front-of-house, training rooms, briefing room, custody anteroom.
Mild negative (−5 Pa): custody cells, decontamination room, kitchen back-of-house and laundry.
Most negative (−15 Pa or lower): forensic PC2 lab where present, hazardous chemical store, battery room, workshop dust extraction.
The apparatus bay is a special case — it sits at slightly negative relative to the corridor (−5 Pa) so that any residual diesel exhaust does not infiltrate the building, but it is single-pass with no recirculation, so the apparatus bay itself does not enter the cascade balance the same way a recirculated space does.
SBKJ machine configuration for emergency services duct fabrication
The duct fabrication brief for a typical Australian emergency services facility looks like this: a high mix of galvanised rectangular and round duct in conventional gauges, a meaningful percentage of stainless duct for decontamination and PC2 exhaust, and a small but security-critical run of heavy-gauge sealed-seam Class A duct for custody cell and watch-house zones. The fabrication shop building this duct needs a machine line that handles both materials, both gauges and both seam styles without setup delays.
The SBKJ recommended configuration for emergency services ductwork fabrication is built around the SBAL-V auto duct production line in its galvanised plus stainless option, with the secure-construction Class A sealed-seam upgrade. The SBAL-V handles galvanised coil from 0.5 mm to 1.5 mm and 304 stainless from 0.5 mm to 1.2 mm on the same line with a tooling changeover sized for production rather than R&D. The Class A sealed-seam upgrade lifts the air-tightness class from default Class C to Class A by adding a sealant-bead application stage in the seam closer, which is the requirement for cell and watch-house duct under AS 4072.1.
The 1.6 mm gauge requirement on secure construction zones is handled on the same line by extending the upper gauge range with a stronger feed and a slower production rate — the machine still runs the same seam profile, simply at the lower production rate appropriate to the heavier gauge. The anti-contraband mesh integration is handled at the register frame fabrication stage, not on the duct line itself.
The complete SBAL-V configuration for an emergency services fabrication shop typically includes the auto duct line, a separate Pittsburgh lock former, a TDF flange line, a coil decoiler with stainless coil capability, a notcher and a folder. Together that line can handle the full mix of duct on a metropolitan-station job at a single-shift output of roughly 350 to 500 metres of rectangular duct per shift.
Worked example — a metropolitan fire station design brief
Consider a typical metropolitan Australian fire station — a four-bay structure with two pumpers, one aerial appliance, one rescue van, an operations office, a watch-room with radio dispatch, a kitchen and mess, a gym, dormitories, a hose drying tower, a bunker gear store, a decontamination room and an SCBA workshop.
The apparatus bay is sized at 8 ACH supply (5,600 m³/h on a 700 m³ bay), balanced by four source-capture exhaust hoses and a general exhaust path returning the bay to slight negative. The supply is heated to maintain 12 °C in winter, exhaust discharges to a roof termination, and CO/NO2 monitoring is continuous with a high-rate purge at 35 ppm CO.
The hose drying tower runs a desiccant dehumidifier holding 40% RH with a heater coil lifting supply to 35 °C. The bunker gear store runs a 5 kW DX heat-pump AHU at 20 °C and 52% RH on a +5 Pa cascade. The decontamination room runs a 7 kW AHU with HEPA on supply, 15 ACH base / 20 ACH boost, dedicated stainless exhaust, −5 Pa. The watch-room sits on NC-30 acoustic ductwork with a 24/7 chilled-water cassette as N+1 backup. Dormitories, kitchen, mess and gym are commercial-grade with kitchen exhaust on a dedicated roof termination.
Fabrication for this single station is dominated by galvanised, with stainless for decontamination, hose tower and any cell duct. A single SBAL-V line running 8 to 12 shifts produces the entire mechanical-services duct package.
Commissioning, witnessing and handover
The commissioning brief on an emergency services facility is heavier than a typical commercial building. The agency client expects witnessed testing of every safety-critical interface, with documented pass/fail records signed by the commissioning agent, the contractor and the agency representative.
The witnessing list typically includes: the cell pressure cascade tested under all door conditions, the apparatus-bay CO and NO2 alarm tested at the trigger setpoints, the apparatus-bay source-capture system tested with a live diesel test source, the decontamination negative pressure tested under door-open conditions, the bunker gear room humidity tested over a 48 hour stabilisation, the communications centre N+1 failover tested with one CRAC physically isolated, the interview room NC-30 acoustic tested with all systems running, the PC2 lab negative pressure tested under all door conditions, the smoke and fire damper actuation tested from the fire panel.
The handover package includes the AS 1851 baseline records for every fire and smoke damper, the operator manuals for the apparatus-bay air quality monitoring, the dehumidifier service intervals for the hose drying tower and the bunker gear store, the filter change schedule for the decontamination room HEPA, the N+1 changeover procedure for the communications centre, and a single-page emergency procedure for the station officer covering switch-to-100-percent-outside-air in a contamination event.
Common procurement mistakes specific to emergency services projects
Across the projects we have supplied duct fabrication machinery to over the past 20 years, the recurring procurement mistakes on emergency services jobs cluster into a short list.
Mistake one — specifying composite duct in the apparatus bay. Polyurethane composite duct is unsuitable for diesel exhaust source-capture and for the thermal cycling of the appliance-bay supply. The duct must be metal.
Mistake two — single-source recirculation off the apparatus bay. Any return-air path that picks up apparatus-bay air and feeds it into office or accommodation space is a categorical breach of NFPA 1500 and every agency standard. Apparatus bay air is single-pass.
Mistake three — undersized hose tower dehumidification. Sizing the hose tower on AS 1668.2 ventilation rates instead of the actual moisture load of the largest expected callout is a common rookie error. The correct sizing is the moisture load, not the air change rate.
Mistake four — missing the cell pressure cascade test on commissioning. The cascade has to be tested under all reasonable door-open and door-closed conditions, not just the nominal balanced state. The agency client will reject the commissioning record if the test was done only at one condition.
Mistake five — fire dampers behind the secure perimeter with no lawful access. The dampers have to be inspectable under AS 1851 for the building life. Burying them inside a Class C cell perimeter with no maintenance access path is a layout error caught at the AS 1851 baseline and adds expense to fix in the field.
Mistake six — galvanised duct on the decontamination exhaust. The chemistry of the cleaning chemicals will rot a galvanised exhaust path in 2 to 3 years. Stainless is the only correct answer.
Mistake seven — single-string cooling on the communications centre. A single CRAC failure during a major incident is a public-safety event. N+1 is the minimum redundancy on any 24/7 communications space.
Mistake eight — NC-40 ductwork on interview rooms. The audible HVAC noise on the recording is grounds for an evidentiary challenge in court. NC-30 minimum, attenuated branches, no in-room return grille.
Pricing and lead time anchors for emergency services duct fabrication
A typical metropolitan Australian fire station of the size above runs to 1,200 to 1,800 m of rectangular duct plus 200 to 300 m of round, 80 to 90% galvanised and 10 to 20% stainless. Fabricating on an SBAL-V line takes 8 to 14 shifts. A police station with watch-house cells, interview rooms and evidence store runs 600 to 900 m rectangular plus 100 to 150 m round at 15 to 25% stainless, fabricating in 5 to 9 shifts.
A typical ambulance base fabricates to 400 to 700 m at a galvanised-dominant mix in 3 to 6 shifts. A single-bay volunteer brigade station runs 200 to 400 m fully galvanised in 2 to 4 shifts. A consolidated regional police-fire-ambulance complex runs 2,500 to 4,000 m in 16 to 28 shifts. The largest projects — a major metropolitan headquarters with a 000 communications centre, PC2 forensic lab and 30-bay vehicle accommodation — can run 6,000 to 10,000 m and fabricate in 40 to 70 shifts.
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FAQ
What ventilation rate is required for a fire station apparatus bay?
A fire appliance bay typically targets 6–10 air changes per hour (ACH) of general ventilation, supplemented by a dedicated vehicle exhaust source-capture system tied to each diesel appliance's tailpipe. Carbon monoxide must be kept below the Safe Work Australia 8-hour OEL of 30 mg/m³ (≈25 ppm), and most modern Australian designs run continuous CO/NO2 monitoring with automatic high-rate purge fans.
What is AS 4072.1 Class C and where does it apply?
AS 4072.1 Class C is the Australian standard for fire-resistant penetration sealing applicable to high-integrity secure construction — used for police custody cells, watch-house holding areas and high-value evidence rooms. In ductwork terms it requires sealed-seam Class A or B construction, 1.2–1.6 mm galvanised or stainless wall thickness, anti-contraband welded mesh at the cell-face register (typically 96 mm clear), and a controlled +5 Pa to −5 Pa pressure cascade between the cell, the anteroom and the corridor.
What humidity and temperature should bunker gear storage be kept at?
18–22 °C dry-bulb and 50–55% RH, with zero direct UV exposure and dedicated air movement to prevent moisture pockets. Storage at higher humidity accelerates aramid degradation and shortens the certified service life of the outer shell; lower humidity below 40% increases brittleness in the moisture barrier. NFPA 1851 and AFAC guidance both align with this band.
How is a 000 dispatch or police communications centre cooled?
24/7 communications centres are designed as N+1 (preferably N+2) redundant cooling rooms with two independent chilled-water risers, dual UPS-fed CRAC units, NC-30 acoustic performance at the operator console, and 22–24 °C dry-bulb with 40–55% RH year-round. Ductwork must be sealed-seam Class A, internally lined where acoustic targets demand, with redundant return paths so the loss of any one branch never takes down the room.
What ductwork material is appropriate for emergency services facilities?
Galvanised steel (Z275 coating, AS 1397) is appropriate for general office, accommodation, training and apparatus-bay supply ductwork. Stainless steel grade 304 is mandated by most state design standards for SCBA decontamination wash rooms, custody-cell exhaust where chemical disinfectants are used, and forensic PC2 containment exhaust. Polyurethane-foam composite ducting is rarely used in emergency services — fire-rating and security cascade requirements push almost everything to metal.
