Multi-Storey Carpark, Basement, Automated Parking, Park-and-Ride and EV Charging Carpark HVAC Duct Guide — AS 1668.2, NCC Class 7a, Jet Fans, Li-Ion Thermal Runaway

Why carpark HVAC is its own discipline

Carpark ventilation is not a simplified version of office or industrial HVAC. It is a discipline with its own controlling standard (AS 1668.2 with a dedicated 1 L/s/m² baseline), its own smoke control regime (AS 1668.1 with jet-fan smoke clearance distinct from the commercial-office atrium model), its own pollutant matrix (carbon monoxide and diesel particulate dominating, with nitrogen dioxide, benzene, formaldehyde and methane in supporting roles), its own NCC building classification (Class 7a is the dedicated parking structure category), and an increasingly distinct set of new hazards as the Australian fleet electrifies — lithium-ion thermal runaway, hydrogen off-gas, hydrogen fluoride and oxygen-rich combustion products that did not feature in any carpark HVAC design ten years ago.

The Australian carpark stock has grown faster than the office tower stock through the last decade. Wilson Parking alone operates over 350 sites across every capital, Secure Parking dominates the CBD tower bundled-parking market, Care Park and Q Park share the second-tier commercial portfolio, EzyPark and Premier Parking handle the suburban and regional sites, and the major airports (Sydney Airport ASX:SYD, Melbourne Airport via APAC, Brisbane Airport, Perth Airport) operate some of the largest single-site enclosed carparks in the country. The Park-and-Ride transit network — Sydney Trains, Sydney Metro, NSW TrainLink, Metro Trains Melbourne, V/Line, Queensland Rail, Transperth and Adelaide Metro — adds tens of thousands of bays at suburban stations, typically open-deck but with enclosed concourse and ANPR-controlled ticketing infrastructure. Automated parking systems have moved from rare to common in inner-CBD residential and mixed-use podium developments by Lendlease (ASX:LLC), Mirvac (ASX:MGR), Crown Group, Frasers Property Australia, Multiplex (Brookfield), John Holland, Hutchinson Builders, Built (Lendlease), ICON Construction and Roberts Pizzarotti.

What unites all of these — and what distinguishes carpark HVAC from every other commercial HVAC vertical — is the controlling pollutant. Office HVAC controls carbon dioxide for occupant comfort. Industrial HVAC controls process-specific contaminants at the source. Hospital HVAC controls airborne pathogens. Carpark HVAC controls carbon monoxide (historically the dominant hazard from cold-start internal combustion engines), diesel particulate matter (now the principal hazard wherever heavy vehicles and old diesel-utility fleets dwell), and increasingly the products of any vehicle fire — which in an electric vehicle includes hydrogen, hydrogen fluoride, oxygen-rich combustion products and a sustained thermal runaway that can last hours and reignite after suppression. The standards (AS 1668.2 nominal rate, AS 1668.1 smoke control, NFPA 88A and NFPA 92 supporting references, NFPA 855 for lithium-ion, AS/NZS 5139 for Australian battery storage) all reflect this pollutant-dominated approach.

This guide is written for the mechanical consultant specifying the ductwork on the next carpark project — whether it is a basement under a 30-storey residential tower in Melbourne CBD, a Park-and-Ride deck at a Sydney Metro station, an EV-only carpark at a destination hotel in Perth, or an automated parking system in a Brisbane Casino Tower residential apartment block. It is not a primer on jet-fan selection or smoke-spill duct sizing in the abstract — the AS 1668 series and the NCC Volume One do those better than any single guide can. It is a practical engineering view of how the carpark types diverge in HVAC ductwork specification, where the new EV-driven hazards fit in, what materials and machinery actually fabricate the ductwork, and which Australian operators, developers and standards bodies drive the procurement decisions.

Carpark types and NCC Class 7a classification

The Australian National Construction Code (NCC) Volume One Class 7a is the dedicated building classification for a carpark — distinct from Class 7b (storage warehouse) and from the office (Class 5), retail (Class 6) and residential (Class 2 or 3) classes that almost always surround it in a mixed-use podium. The Class 7a designation carries its own fire compartmentation, ventilation, smoke control, lighting and accessibility provisions. The mechanical consultant works from the Class 7a chapter and overlays the AS 1668 series.

Multi-storey above-ground (open-deck) carpark. A multi-level parking structure built above grade with at least 1/6 of the perimeter open to atmosphere on each level, qualifying for natural ventilation under AS 1668.2 with supplementary mechanical ventilation only where the floor plate exceeds the natural ventilation pathway depth. Common in airport long-stay parking (Andrews Airport Parking, Park'NGO, Aussie Park Plane), stadium and event parking (MCG, Marvel Stadium, Suncorp Stadium, Adelaide Oval, Optus Stadium, Allianz Stadium), shopping centre parking (Westfield, Vicinity, Stockland centres), and many P&R suburban train stations. Above-ground multi-storey is the lowest-HVAC-intensity carpark type because the natural ventilation handles the majority of the dilution load and mechanical equipment is concentrated at the ramps, deeper floor plates and any enclosed concourse spaces.

Basement (fully enclosed) carpark. A subterranean parking level — typically one to four levels deep — fully enclosed with mechanical ventilation as the only ventilation path. Almost universal in CBD office towers, mixed-use residential towers, hotels, hospitals and shopping centres. The HVAC intensity is the highest of any carpark type because the entire AS 1668.2 nominal 1 L/s/m² rate must be delivered mechanically, the smoke control must work without any natural ventilation assistance, and the carbon monoxide and diesel particulate WES must be held continuously regardless of weather. Basement carparks are the dominant project type for SBKJ ductwork machinery installations in Australia — almost every major mechanical contractor's auto duct line schedule has a basement carpark project on it at any given time.

Automated parking system (APS). A mechanical car-stacker or pallet-conveyor system that removes the human occupant from the parking bay envelope. The driver pulls into an entry vestibule, exits the vehicle, the vehicle is mechanised onto a pallet or platform, and the pallet is conveyed and stacked into a closed mechanical enclosure. Brands include Wohr, Klaus Multiparking, City Parking and Robotic Parking Systems. Significant Australian installations include the Brisbane Casino Towers (Star Entertainment ASX:SGR) and a growing list of Sydney and Melbourne CBD residential developments. The HVAC implication is fundamental — internal combustion CO loads collapse because engines are off in the stacker, but new HVAC loads appear for the mechanical room (high heat from motors and hydraulics), conveyor track (low-rate continuous ventilation), control room (office-grade HVAC), entry vestibule (brief idle CO load) and fire suppression coordination (gaseous suppression typical because water damage on pallets is unrecoverable).

Stack and puzzle parking. Smaller mechanical parking systems, typically two-level or three-level stacker installations in small residential basements where the building footprint cannot accommodate ramp-served bays. Common in inner-Melbourne and inner-Sydney apartment buildings under five storeys. HVAC is closer to a conventional basement carpark — drivers operate the stacker themselves with engine idling, so CO loads are present — but the floor plate is small and the mechanical ventilation is correspondingly modest.

Valet parking. A staffed valet operation where customers hand vehicles to a valet attendant at a porte-cochère and the attendant drives the vehicle to a parking bay (often in a separate basement or off-site facility). Premium examples include Crown Casino Valet (Crown Resorts), The Star Sydney Valet (Star Entertainment ASX:SGR), and the hotel chains (Hilton, Marriott, IHG, Accor, Hyatt at Australian locations). The HVAC consideration is the porte-cochère canopy (brief idle CO load while vehicles queue for valet), the valet desk climate-controlled work area, and any segregated valet-only basement bay configuration that may have different ventilation density to general public parking.

Park-and-Ride (P&R) transit parking. Suburban train station carparks operated typically free of charge by the state rail operators — Sydney Trains, Sydney Metro, NSW TrainLink, Metro Trains Melbourne, V/Line regional, Queensland Rail, Transperth WA and Adelaide Metro. Tier 1 P&R sites at major interchange stations (Parramatta, Strathfield, Hornsby, Box Hill, Footscray, Frankston, Indooroopilly, Beenleigh, Mandurah, Joondalup) have hundreds to thousands of bays, multi-storey deck construction with high natural ventilation, and enclosed concourse spaces for ticketing and amenity. Tier 2 sites at minor stations may be small ground-level lots or single-deck above-ground structures. The HVAC scope is concentrated in the concourse, ticketing kiosk, ANPR enclosure and any commuter amenity, with the parking decks largely naturally ventilated.

CBD commercial parking. Multi-storey CBD parking operated as a commercial business by Secure Parking, Wilson Parking, Care Park, Q Park, EzyPark, Premier Parking and Parkway Holdings, plus the City of Sydney, City of Melbourne and City of Brisbane Council parking divisions. The defining HVAC characteristic is long dwell times (8 to 12 hours for daily commuters, days for monthly tenants), high turnover on peak entry/exit cycles, and shared entry/exit ramps that create pinch points where CO concentration spikes. AS 1668.2 rates are commonly raised to 2 to 3 L/s/m² in the entry/exit ramp zones with dedicated extract above the ramp.

Airport parking. Multi-level enclosed and open-deck parking at Sydney Airport (ASX:SYD multi-storey carparks at Terminal 1, Terminal 2 and Terminal 3), Melbourne Airport (Australian Pacific Airports Corporation, APAC, with multi-storey terminal carparks T1 to T4 and the new Premium Parking Group long-stay), Brisbane Airport (BNE Domestic and International carparks), Perth Airport (T1 to T4 carparks), plus the independent operators Park'NGO, Park'N'Fly Australia, Aussie Park Plane (Sydney), Andrews Airport Parking and Premium Parking Group at major airports. Airport parking has the highest CO and diesel particulate monitoring density because dwell times are extreme (multi-day) and the structures are large multi-storey enclosures with sustained taxi-rank diesel loads at the kerbside drop-off and pick-up zones. Refer the SBKJ Airport and Aviation HVAC Duct Guide for the airport-side detail and airside terminal interface.

EV charging carpark. The newest carpark type and the fastest-growing HVAC subset. EV-only or EV-bay-equipped carparks at destination hotels, commercial offices, shopping centres, transit interchanges and roadside service stations. Operators include Tesla Destination Charging (in hotels and commercial properties — biggest), Tesla Supercharger V3 and V4 (highway and roadside, 250 to 350 kW per port), Chargefox (Carsales-acquired, urban and highway), Evie Networks (highway and regional), NRMA EV, JOLT (kerbside and shopping centre), ChargePoint Australia, Schneider Electric EV, Pulse BP (BP service stations) and Ampol AmpCharge (Ampol service stations). The HVAC overlay is lithium-ion thermal runaway risk per NFPA 855 and AS/NZS 5139 — spark-resistant fans, IECEx Ex-d rated motors, hydrogen detection, 304 stainless extract ductwork, and segregated supply/extract from the general carpark grid.

Stadium and event parking. Multi-storey or large open-lot parking at the major Australian stadiums — Sydney Football Stadium and Allianz Stadium (Sydney), Melbourne Cricket Ground (MCG) and Marvel Stadium (Melbourne), Suncorp Stadium (Brisbane), Adelaide Oval, Optus Stadium (Perth), Bellerive Oval (Hobart). The HVAC characteristic is extreme event surge — thousands of vehicles arriving in a 60 to 90 minute pre-event window and departing in a 30 to 60 minute post-event window. AS 1668.2 demand-controlled ventilation logic must handle the surge without over-ventilating during the long off-peak periods.

Service station and motor fuel dispensing carpark. Petrol and diesel service stations under NFPA 30A motor fuel dispensing standards and Australian counterpart provisions. The HVAC focus is canopy ventilation over the dispensing area (typically open-canopy with natural ventilation), the convenience store and any food service co-located on the forecourt, and increasingly the integrated EV charging bays. Operators include BP (with Pulse BP integration), Ampol (with AmpCharge), Shell Coles Express, 7-Eleven, EG Australia (Woolworths-divested), United, Mobil, Caltex and the independents. NFPA 30A informs the overall fuel-dispensing safety envelope; the carpark portion (parking bays adjacent to the dispensing area) follows AS 1668.2 carpark rates plus the fuel vapour overlay.

Australian commercial carpark operators and developer context

The Australian carpark operator landscape consolidates around a small group of national players. Understanding which operator is on the project drives the specification benchmark, the after-hours operating envelope and the commissioning regime.

Wilson Parking (Wilson Group). The largest operator by site count — over 350 sites across Sydney, Melbourne, Brisbane, Adelaide, Perth, Hobart, Darwin and Canberra. Operates a mix of CBD multi-storey, basement under office towers, shopping centre parking, airport off-site, hospital and university parking. Internal HVAC standards target AS 1668.2 nominal rate plus 15 to 25 percent margin with full CO demand-controlled ventilation across all enclosed sites. The Wilson Storage diversified portfolio includes some hybrid storage-and-parking sites with APS components.

Secure Parking (Park Hill). The largest operator by revenue with significant CBD tower bundled-parking contracts, airport parking operations and hospital parking concessions. Premium specifications driven by tower-owner expectations rather than carpark-operator minimums — typically MERV 11 to 13 filtration on the concourse air, redundant control system architecture, and detailed commissioning regimes.

Care Park (now part of NEC Group). Substantial CBD and suburban portfolio across Melbourne, Sydney and Brisbane. NEC Group integration brings electronic ticketing, ANPR and payment automation as standard, which drives the HVAC requirement for the ANPR enclosure and POS terminal climate control.

Q Park (Q Park Australia). European-origin operator with growing Australian presence focused on CBD and inner-suburban sites. Brings European specification reference points (Eurovent, EN 13779) that frequently exceed AS 1668.2 minimum.

EzyPark, Premier Parking, Parkway Holdings. Mid-tier private operators with suburban and regional site portfolios. Specifications typically follow AS 1668.2 minimum with operational pragmatism — VFD jet fans, simple CO monitoring, and modest concourse climate control.

Crown Casino Valet and The Star Sydney Valet. Premium valet operations at the major Australian integrated resorts. HVAC integration is part of the lobby and front-of-house guest experience — climate-controlled valet desk, porte-cochère with brief idle exhaust extraction, and segregated valet-only basement bays where applicable. Refer the SBKJ Casino and Integrated Resort HVAC Duct Guide for the integrated resort context.

Carpark Operators Council and Parking Australia. The industry bodies that publish technical guidance, run continuing professional development for carpark managers, and represent the operators in regulatory engagement with the state planning authorities, local councils and the National Construction Code review cycle.

City of Sydney, City of Melbourne, City of Brisbane Council parking. Council-operated CBD parking that typically follows AS 1668.2 minimum with strong emphasis on accessibility (AS 2890.6 off-street parking accessibility, DDA compliance) and on integration with the council-managed traffic and signage network (AS 1742, AS 4715 traffic studies).

Sydney Airport, Melbourne Airport, Brisbane Airport, Perth Airport. The major airport corporates each operate their own parking division with multi-level terminal carparks and remote long-stay parking. Specifications routinely exceed AS 1668.2 minimum because dwell times are long, the structures are large, and the airport regulatory environment (refer the SBKJ Airport and Aviation HVAC Duct Guide) layers additional security and emergency response requirements onto the standard carpark provisions.

Property developers. Lendlease (ASX:LLC), Mirvac (ASX:MGR), Crown Group, Frasers Property Australia, Multiplex (Brookfield), John Holland, Hutchinson Builders, Built (Lendlease), ICON Construction and Roberts Pizzarotti all build carpark HVAC into mixed-use podium and stand-alone tower specifications at structural design stage. The decisions taken at concept design determine the carpark HVAC strategy for the building's life — riser locations, plant room size, jet fan layout, EV charging bay provisioning. Late-stage changes are expensive.

Key standards governing carpark HVAC

Carpark HVAC sits at the intersection of more than a dozen overlapping standards. The mechanical consultant identifies the most stringent applicable requirement on each issue and overlays the contractual specification where it goes beyond the minimum.

AS 1668.2 — Mechanical Ventilation in Buildings. The controlling Australian Standard for carpark mechanical ventilation. Sets the nominal 1 L/s/m² baseline for general enclosed carpark, with the rate raised in dwell zones, diesel-truck areas and pinch points. Specifies the carbon monoxide control logic, the demand-controlled ventilation approach, and the supplementary natural ventilation rules. The single most cited carpark HVAC document in Australia.

AS 1668.1 — Fire and Smoke Control in Buildings. The Australian Standard for carpark smoke control. Sets out the fire-mode air-change requirement (typically 6 ACH for smoke clearance), the stair pressurisation 50 Pa requirement, the lift lobby pressurisation Type C provisions, the jet-fan switchover logic on fire detection, and the smoke-spill duct fire resistance level. Mandatory for any enclosed carpark above the NCC threshold.

AS 4254 — Ductwork for Air Handling Systems. The Australian Standard for ductwork construction. Applies to all carpark HVAC ductwork alongside SMACNA and DW/144 in domestic specifications.

AS 1530.4 — Fire Resistance Tests. The fire resistance rating standard for ductwork penetrating fire-rated floors and walls. Smoke-spill ductwork from carpark fire zones is typically rated 600 degrees Celsius for 120 minutes. Fire dampers at fire compartment boundaries follow AS 1530.4 and AS 1851 annual testing.

AS 1851 — Routine Service of Fire Protection Systems. The annual testing regime for fire dampers, smoke-spill fans, jet-fan fire-mode operation and CO monitoring sensor calibration. Applies for the life of the building, not just at handover.

AS 1657 — Platforms, Walkways, Stairways and Ladders. Applies to maintenance access platforms at the jet fans, exhaust trunks and rooftop plant. Coordination is mandatory at design stage because retrofitted access platforms cost three to five times design-stage platforms.

NCC Class 7a — Parking Structure. The dedicated National Construction Code building classification for a carpark. Class 7a carries separate fire compartmentation, ventilation, smoke control, lighting, accessibility and structural provisions from the surrounding Class 5, 6 or 7b uses in a mixed-use podium.

AS 2890 series — Parking facility design. AS 2890.1 (off-street car parking), AS 2890.2 (off-street commercial vehicle facilities), AS 2890.3 (bicycle parking), AS 2890.5 (on-street parking) and AS 2890.6 (off-street parking for people with disabilities — DDA compliance). The 2890 series drives the bay geometry, ramp slope, ceiling height and accessibility provisions that frame every HVAC ductwork layout decision.

AS 4715 — Traffic and parking studies. The methodology for measuring vehicle movement, peak occupancy and queue length. Informs the demand-controlled ventilation set-point logic and the entry/exit pinch-point ventilation sizing.

NFPA 88A — Parking Structure. The United States standard for parking structure fire and life safety. Referenced as a technical source in Australian specifications alongside AS 1668.1, particularly for the smoke clearance air-change calculation and the integration with sprinkler protection per AS 2118.

NFPA 92 — Standard for Smoke Control Systems. The international high-rise smoke management reference. Applies in carpark contexts where the carpark connects to an adjoining atrium, lobby or multi-storey enclosed shaft.

NFPA 855 — Standard for the Installation of Stationary Energy Storage Systems. The lithium-ion battery installation standard. Increasingly cited in EV charging carpark specifications because the energy stored in a parked EV battery (60 to 120 kWh per vehicle, multiplied by the number of vehicles in a basement) exceeds the threshold that NFPA 855 was originally written for in stationary BESS contexts. Refer the SBKJ EV Charging Hub and BESS HVAC Duct Guide.

AS/NZS 5139 — Electrical Installations — Safety of Battery Systems for Use With Power Conversion Equipment. The Australian/New Zealand standard for battery storage equipment up to 200 kWh — relevant to BESS rooms co-located with carparks (peak shaving, EV charging support) and to the broader Australian regulatory context for lithium-ion installation safety.

NFPA 30A — Motor Fuel Dispensing Facilities and Repair Garages. The United States standard for petrol and diesel service stations. Informs the Australian carpark specification where the parking structure is part of a service station forecourt or adjoins the fuel dispensing area.

AS 3000 — Electrical Installations. The Australian wiring rules. Applies to the carpark electrical installation including the EV charging infrastructure, jet-fan motor wiring, fire detection wiring and emergency lighting.

AS/NZS 3008 — Electrical Installations — Selection of Cables. The cable selection standard for the carpark electrical installation. Important for EV charging cable sizing where the per-port load can exceed 100 A at 400 V DC.

AS 4214 — Gaseous fire-extinguishing systems. The Australian standard for gaseous suppression — applicable to APS (automated parking system) installations and to premium properties where water sprinkler damage would be unrecoverable.

AS 2118 — Sprinkler Systems. The Australian sprinkler standard. Applies to most enclosed carparks except those replaced with gaseous suppression for specific reasons.

AS 1670 — Fire Detection, Warning, Control and Intercom Systems. The fire detection standard. Drives the smoke detector and gas detector grid that feeds the AS 1668.1 fire-mode logic.

ACMA Telecommunications. The Australian Communications and Media Authority regulates the NBN, 4G and 5G connectivity used for ANPR (Automatic Number Plate Recognition), POS payment terminals, BMS uplinks and management system telemetry. ACMA licensing applies to the carpark telecommunications enclosures.

Privacy Act 1988 and Australian Privacy Principles (APPs). Federal privacy legislation that governs the cardholder data captured at the POS payment terminal and the personal information (vehicle registration) captured by the ANPR system. The ANPR backend server room and the POS data flow require Privacy Act-compliant data handling, which intersects with the HVAC redundancy requirements for the server room.

AS/NZS 1170.2 — Wind actions. The Australian wind load standard. Applies to rooftop discharge stacks and any wind-exposed ductwork on multi-storey carpark roofs.

AS 1742 — Manual of Uniform Traffic Control Devices. The Australian traffic signage standard. Coordinates the carpark wayfinding and directional signage with the local council traffic management.

State planning authorities (DA — Development Approval) and local council planning. The state planning departments (NSW DPHI, Victorian DTP, Queensland DSDILGP, WA DPLH, SA DIT) and local councils issue development approvals that often include specific carpark ventilation and smoke control conditions, particularly for sites near residential zones where rooftop discharge emissions are scrutinised.

Workplace exposure standards — the controlling pollutants

The Australian workplace exposure standards (WES) published by Safe Work Australia define the maximum 8-hour time-weighted average and short-term exposure limit (STEL) concentrations for airborne contaminants in occupational settings. In a carpark, the WES is the controlling design input because the workers (cleaners, security guards, valet attendants, maintenance) and members of the public must remain below the WES for the duration of their exposure. The AS 1668.2 nominal 1 L/s/m² is the regulatory floor; the WES is the operational ceiling.

Carbon monoxide (CO) — 30 ppm 8-hour TWA. The historical dominant carpark pollutant. CO is produced by cold-start internal combustion engines — the highest emission rate is in the first 30 to 60 seconds of cold-start before the catalytic converter reaches operating temperature. CO is colourless, odourless, binds to haemoglobin 250 times more readily than oxygen, and causes headaches at 50 ppm and unconsciousness at 1,200 ppm. The 30 ppm 8-hour TWA is the design target for the demand-controlled ventilation logic across every enclosed Australian carpark. As the fleet electrifies (target 2030 50 percent new-vehicle EV in some scenarios), the average CO loading declines but the WES design target does not change because a single cold-start petrol vehicle in a confined space can still spike local CO well above 30 ppm.

Diesel particulate matter (DPM) — elemental carbon 0.1 mg/m³ TWA. The principal pollutant in any carpark with significant diesel traffic — taxi ranks, fleet utility bays, loading docks, airport kerbside drop-off and pick-up, hospital ambulance bays and any commercial parking with heavy vehicle access. DPM is a Group 1 IARC carcinogen, and the elemental carbon fraction (the carbonaceous core of the particle, not the total particulate mass) is the regulatory metric. The 0.1 mg/m³ 8-hour TWA is significantly more stringent than the general respirable dust standard and drives the requirement for raised ventilation rates (2 to 5 L/s/m²) in diesel-heavy zones. EURO 6 (Australian Design Rule ADR 79/04) diesel vehicles emit roughly 90 percent less DPM than EURO 4 vehicles, but the older fleet remains a significant share of the on-road population through the late 2020s.

Nitrogen dioxide (NO2) — 5 ppm STEL. A combustion product from modern petrol and diesel engines, more prominent in EURO 6 vehicles than older specifications because the lean-burn combustion strategy produces higher NO2 per unit of CO. The 5 ppm STEL is the design ceiling for short-term exposure events such as peak entry/exit pinch points. The demand-controlled ventilation logic typically uses CO as the primary control variable with NO2 as a supplementary trigger in modern fleet scenarios.

Formaldehyde (HCHO) — 1 ppm STEL. A new-build off-gassing pollutant from carpark wall paint, polymeric flooring sealant, polymer-bonded concrete additives and any timber composite elements. The 1 ppm STEL applies during the first six to 18 months after construction. Specify enhanced ventilation during the building commissioning phase to clear formaldehyde before occupancy.

Volatile organic compounds (VOCs) — general standard. Fuel vapour from parked vehicles (typical evaporative emission from a sealed fuel tank is 0.05 to 0.2 grams per day per vehicle), spillage at the entry/exit ramp and accidental fuel release at any service station forecourt all contribute VOC load. AS 1668.2 nominal ventilation handles routine VOC under normal operation; spillage events require manual operator intervention.

Benzene (C6H6) — 1 ppm STEL. A specific VOC of regulatory concern because of its Group 1 IARC carcinogen status. Benzene is a component of older Australian petrol (declining from approximately 5 percent benzene in 1990s petrol to under 1 percent in current Australian Standard petrol). As the fleet electrifies and petrol formulation improves, benzene exposure declines but the WES remains a design reference for older fleet scenarios.

Methane (CH4) — 1.25 percent of 25 percent LEL. A potential flammable gas hazard from LPG-powered taxis and LPG-powered forklifts operating in any service yard or loading dock co-located with the carpark. The 25 percent LEL threshold is the alarm setpoint for gas detection wired to rapid HVAC switchover (purge ventilation). Spark-resistant fans and IECEx Ex-d motors are mandatory in any LPG-bay extract path.

Hydrogen (H2) — 25 percent LEL. The thermal-runaway off-gas from a lithium-ion battery in extreme failure mode. The 25 percent LEL threshold for hydrogen drives the spark-resistant extract fan and the IECEx Ex-d motor specification in EV charging carpark Li-ion thermal-runaway extract paths. Hydrogen is the principal hazard in the early stage of a thermal-runaway event (cell venting before the propagation to other cells in the pack). NFPA 855 Chapter 14 and AS/NZS 5139 cover the detection and ventilation response.

R32, R410A, R744 refrigerant. The current generation of HVAC refrigerants used in EV charging cooling and in the general carpark concourse climate control. R32 (mildly flammable A2L), R410A (non-flammable A1, being phased out under HFC regulation) and R744 (CO2 natural refrigerant, A1) all have refrigerant leak detection and ventilation requirements covered in AS/NZS 1677, AS/NZS 5149 and AS/NZS 5141. Specify refrigerant leak detection in any enclosed plant room where R32 inventory exceeds the A2L threshold.

Basement carpark mechanical ventilation — the core design problem

The fully-enclosed basement carpark is the dominant HVAC project type for SBKJ ductwork machinery installations in Australia. Almost every CBD office tower, mixed-use residential development and hospital campus has a basement carpark, and the basement carpark mechanical ventilation is one of the largest single ductwork scopes in the building.

The AS 1668.2 nominal 1 L/s/m² baseline translates to approximately 6 air changes per hour at a 2.4 metre ceiling height, or 5.3 ACH at the 2.7 metre commercial ceiling height. For a typical 5,000 square metre basement carpark at 2.4 metre ceiling, the nominal rate is 5,000 L/s or 5 m³/s, scaling to 18,000 m³/h. That is a significant air handling load that must be delivered continuously during operating hours.

In practice, the nominal rate is the regulatory floor and the operational rate is set by the demand-controlled ventilation logic targeting carbon monoxide 30 ppm 8-hour TWA and diesel particulate 0.1 mg/m³ TWA. The CO sensors are installed at 1.5 metre breathing height on a 25 to 50 metre grid through the carpark, wired to a VFD jet-fan controller and a CO Auto-Tune Cooling logic (typical brand ATC) that modulates jet-fan speed and primary supply/exhaust fan speed. The result is a typical operational rate of 30 to 70 percent of the nominal full-rate during normal operation, with peak full-rate triggered on entry/exit surge events, on CO concentration above 25 ppm rolling average, or on the operator manually overriding for cleaning or maintenance.

The ventilation grid configuration divides into three categories. The fully-ducted ventilation grid runs supply ductwork to multiple distributed outlet diffusers and return ductwork to multiple distributed return grilles across the carpark — this configuration is now relatively rare in new-build Australian basement carparks because the duct distribution and the head room consumption exceed the practical envelope. The jet-fan ducted system runs supply duct riser at one end of the carpark, jet fans (200 to 450 mm diameter at 6 to 12 m/s discharge velocity) arranged in a herringbone or longitudinal pattern through the soffit, and exhaust duct riser at the opposite end — this is the dominant new-build configuration in Australia because the head room and duct distribution penalty is minimised and the fire-mode smoke clearance operation works well within the same fan grid. The hybrid ducted-and-jet-fan configuration uses primary supply and exhaust risers with jet fans driving local circulation in deeper or more complex floor plates — common in airport, hospital and university campus parking where the floor plate exceeds 8,000 to 12,000 square metres.

SBKJ ductwork machinery supports all three configurations. The SBAL-V auto duct line fabricates galvanised G90 (Z275) rectangular ductwork at 0.6 to 1.5 millimetre thickness for the primary supply and exhaust risers. The SBSF-1525 spiral tubeformer and SBFB-1500 spiral former handle the round duct connections at the jet fans and the tall multi-storey return risers up to 1,500 millimetre diameter. The SBTF-2020 auto duct line fabricates the largest rectangular ductwork (up to 2,000 millimetre width) for the primary smoke spill main duct from the basement fire zone to the rooftop discharge. The SBPC1500 plasma cutter handles bespoke tap-ins, access panels and transitions. The SB-ZF1500 stitchwelder produces the tight-pressure-rated jet fan housings. The SBLR-600 longitudinal seam welder produces heavy-gauge generator exhaust ductwork.

Jet fan layout and aerodynamic design

The jet fan layout is the single most influential carpark HVAC design decision in any Australian basement project. Get it right and the AS 1668.2 nominal rate flows naturally through the carpark with low fan energy and effective fire-mode smoke clearance. Get it wrong and the operator faces persistent CO accumulation zones, headaches from staff complaints, fire-engineering rework and ultimately a non-compliant carpark.

The jet fan operates by entraining surrounding air into a high-velocity jet, multiplying the volumetric flow by a factor of 5 to 15 times the fan discharge volume. A 300 millimetre diameter jet fan with 8 m/s discharge velocity produces 0.56 m³/s of discharge volume but entrains 3 to 8 m³/s of carpark air into the directed flow. The result is bulk air movement across the carpark from the supply duct to the exhaust duct without requiring a dense network of distributed supply outlets.

The herringbone layout arranges jet fans at 30 to 45 degrees offset from the carpark long axis, with alternating fans on opposite walls or soffit positions. The geometry creates a serpentine bulk air flow that covers the floor plate uniformly. Best suited to rectangular floor plates with the long axis ratio under 4:1 and ceiling heights above 2.4 metres. The longitudinal layout arranges jet fans in a continuous line along the carpark long axis, all driving in the same direction. The geometry creates a piston-flow bulk air flow from supply to exhaust. Best suited to elongated floor plates with the long axis ratio above 4:1 and where the carpark has predominantly one entry/exit direction.

The hybrid layout combines herringbone primary jet fans with localised auxiliary jet fans at pinch points (ramps, columns, near-stair entries). Best suited to complex floor plates with significant column density, multiple ramps, mixed bay orientation or where the ceiling height varies across the floor plate.

Common Australian jet fan brands include Aerolite, JetVent, Sanyo and Cyclonix Wirsbo. The selection criteria include the discharge velocity (typically 6 to 12 m/s for normal mode and up to 20 m/s for fire-mode smoke clearance), the noise emission at the discharge (typically 65 to 80 dBA at 1 metre, which is acceptable in a carpark but must be coordinated with any adjoining noise-sensitive use), the IP rating (typically IP55 minimum for basement environments), and the spark-resistance rating (mandatory for any LPG-bay extract path and for EV charging carpark Li-ion thermal-runaway extract).

The jet fan housing is fabricated typically from galvanised G90 (Z275) sheet at 1.0 to 1.5 millimetre thickness, stitchwelded on the SBKJ SB-ZF1500 stitchwelder for tight pressure rating. The stitchweld is preferred over continuous weld because it produces a faster, lower-distortion seam at the pressure rating required for jet fan operation. The housing connects to the supply duct via a flanged connection (typically TDF transverse duct flange) at 200 to 450 millimetre diameter, depending on the jet fan model.

Demand-controlled ventilation logic and CO monitoring

Demand-controlled ventilation tied to carbon monoxide monitoring is now standard practice in every Australian enclosed carpark of any size. The logic reclaims 30 to 70 percent of the AS 1668.2 nominal-rate fan energy under typical Australian operating profiles, while maintaining CO below the 30 ppm 8-hour TWA at all times.

The sensor grid installs carbon monoxide sensors at 1.5 metre breathing height on a 25 to 50 metre grid through the carpark. The grid density is set by the AS 1668.2 commissioning requirement to demonstrate that no point in the carpark exceeds the WES — a sparser grid risks missing local CO accumulation zones, particularly near columns, ramps and corners where the bulk air flow has dead zones. The sensors are typically electrochemical CO cells with a 12 to 24 month replacement cycle and integral self-test logic that flags sensor degradation to the BMS.

The control logic is typically an ATC (CO Auto-Tune Cooling) algorithm that modulates jet-fan speed and primary supply/exhaust fan speed based on the maximum CO concentration measured across the sensor grid (not the average — the maximum is the regulatory metric). The algorithm has a deadband (typically 5 ppm) and a rate-of-change trigger that anticipates entry/exit surge events by ramping fan speed before the CO concentration peaks.

The diesel particulate sensor grid is added in diesel-heavy zones (taxi ranks, fleet utility bays, loading docks, airport kerbside, hospital ambulance bays). Diesel particulate sensors are typically optical scatter or laser scatter instruments calibrated against the elemental carbon fraction. The grid density is similar to the CO grid, and the alarm setpoint is 0.1 mg/m³ rolling 8-hour TWA.

The nitrogen dioxide sensor grid is increasingly added in modern-fleet scenarios where EURO 6 vehicles dominate. NO2 sensors are typically electrochemical cells similar to CO sensors. The alarm setpoint is 5 ppm STEL (short-term exposure limit) and the control logic typically uses NO2 as a supplementary trigger to the primary CO logic.

The BMS integration ties the carpark ventilation control to the building management system for after-hours reduced-rate operation, peak-event manual override, fire-mode switchover, alarm escalation and maintenance scheduling. Typical BMS protocols include BACnet IP, Modbus TCP and proprietary brand-specific protocols. The BMS uplink to the carpark operator's central monitoring (Wilson Parking, Secure Parking, Care Park, Q Park central operations) is typically via NBN or 4G/5G modem with cellular redundancy.

AS 1668.1 jet-fan smoke control — the fire-mode design

On fire detection — typically a smoke detector trip or a manual call point activation — the mechanical ventilation system switches from demand-controlled mode to AS 1668.1 fire-mode smoke clearance. The switchover is automatic, completes within seconds, and is the most critical commissioning test in any carpark HVAC project.

Fire-mode operation drives the jet fans in a defined direction to clear smoke from the fire-affected bay toward an emergency exhaust outlet. The air-change rate is typically 6 ACH (compared with the demand-controlled mode 30 to 70 percent of nominal). The jet fans switch from variable-speed normal-mode operation to fixed-speed maximum-output fire-mode operation, with the discharge velocity rising from typical 8 m/s normal to 15 to 20 m/s fire-mode. The primary supply and exhaust fans switch from variable-speed to maximum-output.

Stair pressurisation maintains 50 Pa positive pressure differential with all doors closed and 8 m/s air velocity through one open door at the discharge level. The stair pressurisation duct is a dedicated supply duct routed from a rooftop intake or a basement-level supply fan to the stair shaft top, with no shared connection to the general carpark ventilation grid. Tight-leakage ductwork is mandatory — leakage above 3 percent defeats the pressurisation calculation. SBKJ TDF flange forming achieves the Class C leakage performance required for stair pressurisation duct.

Lift lobby pressurisation (Type C per AS 1668.1) maintains positive pressure in the lift lobby relative to the carpark fire zone, preventing smoke migration into the lift shaft. The Type C pressurisation supply is a dedicated duct from a separate supply fan, with similar tight-leakage requirements to the stair pressurisation. Refer the SBKJ Commercial Office Tower HVAC Duct Guide for the high-rise lift lobby pressurisation detail in the tower above the carpark.

Smoke spill ductwork carries the smoke from the carpark fire zone to the rooftop discharge. The smoke spill duct is typically 1,500 to 2,000 millimetre rectangular width — SBKJ SBTF-2020 auto duct line fabricates this size in galvanised G90 (Z275) — and rated 600 degrees Celsius for 120 minutes per AS 1530.4. The fire-rating envelope is typically achieved by encasing the smoke spill duct in 2-hour fire-rated plasterboard or board fire wrap, with the duct itself uninsulated. Fire dampers at every fire compartment boundary follow AS 1530.4 and AS 1851 annual testing. Allow access panels at every fire damper for annual inspection.

The smoke-spill fan is rated for high-temperature operation — typical specification F300 (300 degrees Celsius for 60 minutes), F400 (400 degrees Celsius for 90 minutes) or F600 (600 degrees Celsius for 120 minutes) per EN 12101-3 or equivalent. The fan motor is mounted outside the smoke air stream where possible, with shaft seal and bearing design suitable for high-temperature exposure. Refer the SBKJ Fire and Smoke Damper HVAC Duct Integration guide for the damper coordination detail.

Automated parking system (APS) HVAC — a separate discipline

Automated parking systems are a small but rapidly growing subset of Australian carpark projects, particularly in inner-CBD residential and mixed-use podium developments where the building footprint cannot accommodate the ramp-served bays of a conventional basement carpark. The most prominent Australian APS installations are at the Brisbane Casino Towers (Star Entertainment ASX:SGR) and a growing list of Sydney and Melbourne CBD residential developments by Mirvac, Lendlease and Crown Group. Brands include Wohr, Klaus Multiparking, City Parking and Robotic Parking Systems.

The APS fundamentally changes the carpark HVAC calculation because the human occupant is removed from the parking bay envelope. The driver pulls the vehicle into an entry vestibule, exits the vehicle, the vehicle is mechanised onto a pallet or platform, and the pallet is conveyed and stacked into a closed mechanical enclosure. The driver never enters the stacker proper. The engine is switched off at the entry vestibule. Internal combustion CO loads in the bays collapse because the engine runs only during the brief entry vestibule dwell.

But new HVAC loads appear. The mechanical room — housing the motors, hydraulic pumps, control panels and conveyor drive — has a high heat load from motor inefficiency and hydraulic pressure-drop losses. Typical APS mechanical room heat load is 5 to 15 kW per 100 stalls of capacity, requiring dedicated ventilation and supplementary cooling. The conveyor track — the enclosed shaft through which the pallets move between levels — requires low-rate continuous ventilation to clear motor heat, lubricant vapour and any residual fuel vapour from a parked vehicle. The control room (often staffed during operating hours) requires office-grade HVAC and AS 1668.2 office ventilation rates (10 L/s per person). The entry vestibule — where the driver dismounts with engine running for the brief mechanisation cycle — requires enhanced ventilation to clear the brief idle CO load.

Fire suppression strategy shifts from sprinkler-only to gaseous suppression (AS 4214) in many APS installations. The reason is unrecoverable water damage — a sprinkler discharge into the stacker enclosure would soak every pallet and every vehicle in the stack, with water damage and electrical fault costs that would write off the entire APS. Gaseous suppression (typically inert gas IG-100 nitrogen, IG-541 Inergen, FK-5-1-12 Novec 1230 or HFC-227ea FM-200) suppresses the fire without water damage. The HVAC implication is that the APS enclosure must be sealed sufficiently to maintain the gaseous suppression concentration for the design hold time (typically 10 minutes minimum), and the post-discharge ventilation must be coordinated with the suppression system.

SBKJ recommends fully ducted SBAL-V galvanised supply and 304 stainless extract for the APS mechanical room (extract carries motor heat and trace lubricant vapour, so 304 stainless extends service life), and SBFB-1500 spiral risers for the conveyor track ventilation. The control room is conventional office-grade HVAC. The entry vestibule is conventional carpark HVAC with enhanced supply rate. The gaseous suppression coordination is with the fire engineer and the APS OEM.

Entry concourse, ticketing kiosk, ANPR and POS HVAC

The entry concourse is the architectural and operational interface between the carpark and the user. It contains the boom gate, the ticketing kiosk, the ANPR camera enclosure, the POS payment terminal and frequently a small concierge or security guard room. The HVAC must hold office-grade thermal comfort and indoor air quality in a space that is constantly opening and closing to the carpark and the outside environment.

The ticketing kiosk is typically a small enclosed booth with a vending machine, intercom and CCTV. AS 1668.2 office ventilation rate (10 L/s per occupant, even though the kiosk is unstaffed in most modern carparks) is the minimum. The enclosure houses electronics that must be kept below 40 degrees Celsius internal ambient — dedicated cooling is typically provided by a small split-system air-conditioner with condenser mounted externally to the carpark structure.

The ANPR (Automatic Number Plate Recognition) camera enclosure is mounted at the boom gate and at the exit gate. The camera, illuminator and processing unit dissipate 50 to 200 watts of heat and must be kept below 50 degrees Celsius. Direct solar gain is a significant issue for outdoor-mounted ANPR — the enclosure typically has shading and ventilation slots designed to clear convective heat without admitting rain or dust. Indoor-mounted ANPR (under canopy) is simpler thermally but requires coordination with the canopy HVAC.

The POS payment terminal is typically mounted on a payment kiosk in the entry concourse or at a free-standing pay station inside the carpark. The POS electronics dissipate 30 to 100 watts and require ambient cooling below 40 degrees Celsius. The POS captures cardholder data — credit card numbers, expiry dates, CVV codes — which is regulated under the Payment Card Industry Data Security Standard (PCI DSS) as well as the Privacy Act 1988. The PCI DSS data flows from the POS to the carpark operator's payment processor via the ACMA-licensed NBN or 4G/5G connection.

The concierge or security guard room is typically a small enclosed office (typically 5 to 15 square metres) with full-time staff during operating hours, CCTV monitoring, intercom to ticketing kiosk, and direct access to the carpark. AS 1668.2 office ventilation (10 L/s per person), MERV 11 to 13 filtration, and conventional split-system or hydronic conditioning. The room may include a small breakroom with kettle and microwave, requiring enhanced exhaust per AS 1668.2.

SBKJ recommends SBAL-V galvanised duct at 0.6 to 0.8 millimetre thickness for all entry concourse HVAC supply and return ductwork, with conventional flexible duct branches to the diffusers. The ductwork is segregated from the carpark main ventilation grid to maintain office-grade indoor air quality without exposure to the carpark CO and DPM load.

Valet parking HVAC — premium hotel and integrated resort context

Valet parking is the premium delivery model for parking at high-end hotels, integrated resorts and major event venues. The driver hands the vehicle to a valet attendant at the porte-cochère, the attendant drives the vehicle to a parking bay (often in a separate basement or off-site facility), and the vehicle is retrieved on demand. Premium Australian valet operations include Crown Casino Valet (Crown Resorts at Crown Melbourne, Crown Perth and Crown Sydney) and The Star Sydney Valet (Star Entertainment ASX:SGR at The Star Sydney, The Star Gold Coast and the Brisbane Casino Towers).

The HVAC scope for valet parking has three distinct zones. The porte-cochère canopy is the front-of-house arrival point. Vehicles queue briefly with engines idling while the valet attendant takes the keys and the driver enters the lobby. The canopy is typically partially open to atmosphere on one or two sides, but the queue can produce a measurable CO load if the canopy is enclosed on three sides or the queue extends for several minutes. AS 1668.2 enhanced ventilation at the canopy zone (typically 2 to 4 L/s/m²) clears the idle exhaust. SBAL-V galvanised duct connects the canopy supply to a roof-mounted supply fan.

The valet desk is the staffed work area where attendants log keys, process valet tickets and coordinate vehicle retrieval. Typically a small enclosed office adjoining the porte-cochère with conventional office-grade HVAC. AS 1668.2 office rates, MERV 11 to 13 filtration, and acoustic separation from the porte-cochère for telephone use.

The valet basement bay is the dedicated parking area for valet-parked vehicles. Depending on the operator's policy and the building configuration, valet bays may be segregated from public parking (different access, different security) or integrated with the general basement carpark. The HVAC follows conventional basement carpark provisions — AS 1668.2 nominal rate, CO demand-controlled ventilation, AS 1668.1 fire-mode smoke control. Coordination with the front-of-house lobby HVAC is critical because the valet driveway is acoustically and architecturally part of the guest arrival experience.

Refer the SBKJ Casino and Integrated Resort HVAC Duct Guide for the broader integrated resort HVAC context and the SBKJ Hotel and Hospitality HVAC Duct Guide for the hotel front-of-house HVAC interface.

Park-and-Ride (P&R) transit carpark HVAC

Park-and-Ride carparks at suburban train stations are operated typically free of charge by the state rail operators. The major operators are Sydney Trains and NSW TrainLink (Sydney suburban), Sydney Metro (the new automated metro lines), Metro Trains Melbourne and V/Line (Melbourne suburban and regional), Queensland Rail (Brisbane suburban and regional), Transperth (WA Perth and regional) and Adelaide Metro (SA Adelaide).

Tier 1 P&R sites at major interchange stations have hundreds to thousands of bays and significant infrastructure. Examples include Parramatta, Strathfield, Hornsby, Penrith and Liverpool (Sydney); Box Hill, Footscray, Frankston, Dandenong and Sunshine (Melbourne); Indooroopilly, Beenleigh, Caboolture and Robina (Brisbane); Mandurah, Joondalup and Murdoch (Perth); Mawson Lakes, Salisbury and Gawler (Adelaide). The HVAC scope concentrates on the enclosed concourse spaces, the ticketing infrastructure, the ANPR enclosures and any commuter amenity (restrooms, kiosks, taxi waiting areas), with the parking decks largely naturally ventilated as open-deck or partially enclosed multi-storey structures.

Tier 2 P&R sites at minor stations are smaller — typically a single deck or ground-level lot — and the HVAC scope is correspondingly modest, often limited to the ticketing kiosk and a small restroom amenity.

The material specification for P&R follows the coastal proximity rule. Sites within 5 kilometres of the marine atmosphere (the majority of Sydney harbourside, Brisbane River, Adelaide gulf, Perth coastal stations) specify 304 or 316 stainless steel for the exhaust trunk and any duct exposed to marine atmosphere infiltration. Inland sites specify galvanised G90 (Z275). All sites use SBAL-V auto duct line fabrication.

Jet fans are specified only where the enclosed deck depth exceeds the natural ventilation pathway — typically the entry ramp zone, the inner-deck areas of large multi-storey P&R structures, and the connector tunnel between the carpark and the station concourse where applicable. The SBKJ SB-ZF1500 stitchwelder fabricates the jet fan housings for P&R installations.

The ANPR system at P&R sites is typically simpler than at commercial CBD carparks because the free-of-charge operating model removes the payment integration. ANPR at P&R is used for traffic management, security monitoring and operator data analytics rather than payment enforcement. The ANPR enclosure HVAC follows the same provisions as the commercial CBD model — small enclosed booth with dedicated cooling, segregated from the carpark main ventilation grid.

State planning authority coordination is significant for P&R because the sites are state-owned and the development approvals are issued by the state planning departments rather than local councils. The state planning conditions often specify the carpark ventilation discharge stack height, the rooftop emission control and the noise emission to adjoining residential zones.

CBD commercial parking — long-dwell HVAC

CBD commercial multi-storey parking — operated by Secure Parking, Wilson Parking, Care Park, Q Park, EzyPark, Premier Parking and the council parking divisions — is the dominant pay-parking model in every Australian capital city CBD. The defining HVAC characteristic is the long dwell time profile.

Daily commuter parking has dwell times of 8 to 12 hours per vehicle — the commuter parks in the morning, works the day in the office above, and retrieves the vehicle in the evening. Monthly tenant parking has dwell times of multiple days to weeks. Hourly visitor parking has dwell times of 1 to 4 hours. The mix varies by site — CBD core sites near major office towers are dominated by daily commuter and monthly tenant, while CBD fringe sites near retail and hospitality precincts have more hourly visitor.

The HVAC implication is that the carbon monoxide loading concentrates at the peak entry/exit cycles — morning 7am to 9am, evening 5pm to 7pm — while the off-peak periods see minimal vehicle movement and very low CO accumulation. Demand-controlled ventilation logic targets a low background rate (typically 30 to 40 percent of nominal) during off-peak with rapid ramp to full nominal during entry/exit surge.

The entry/exit ramp zone is the critical pinch point. Vehicles queue at the ramp during peak entry/exit with engines running, producing localised CO concentration that can exceed the carpark average by a factor of 3 to 5. AS 1668.2 rates in the ramp zone are commonly raised to 2 to 3 L/s/m² with dedicated extract above the ramp ceiling. The ramp ventilation switches on automatically when CO at the ramp sensor exceeds 25 ppm rolling average.

The booth-operated payment kiosk (where the carpark still uses staffed payment rather than automated POS) requires separate climate-controlled HVAC with AS 1668.2 office rates. The booth is typically a small enclosed cabin at the entry/exit ramp with full-time staff during operating hours, intercom to the ticketing system and direct view of the gate.

Airport parking — large scale, long dwell, taxi rank diesel

Airport parking is the highest-HVAC-intensity carpark vertical in Australia. The major airports operate multi-level enclosed and open-deck parking at scales that dwarf any other carpark project type — Sydney Airport (ASX:SYD) Terminal 1, Terminal 2 and Terminal 3 carparks, Melbourne Airport (APAC) T1 to T4 carparks, Brisbane Airport BNE Domestic and International carparks, Perth Airport T1 to T4 carparks. Independent operators including Park'NGO, Park'N'Fly Australia, Aussie Park Plane (Sydney), Andrews Airport Parking and Premium Parking Group operate substantial off-airport long-stay parking that frequently exceeds the airport-operated facilities in capacity.

The dwell time profile is extreme. International travel parking has dwell times of multiple days to weeks per vehicle. Domestic business travel parking has dwell times of 1 to 3 days. Holiday travel parking has dwell times of 1 to 3 weeks. The combined effect is that the parked vehicle population evolves slowly over a multi-day timescale, and the carbon monoxide loading from cold-start vehicles is concentrated at the arrival/retrieval cycles rather than distributed across the day.

The kerbside drop-off and pick-up zones at the airport terminals are sustained taxi-rank diesel sources. The drop-off zone has taxis, rideshare vehicles, hotel shuttles and private cars idling while passengers and bags transfer. The pick-up zone has the same population on the inbound side. Diesel particulate loading at the kerbside is the highest in any Australian carpark vertical, and AS 1668.2 rates at the kerbside are commonly 3 to 5 L/s/m² with dedicated diesel particulate sensors.

The HVAC scope for airport parking is large. Primary supply and exhaust risers run from rooftop plant to every level, with SBAL-V galvanised duct fabrication. Jet fans run through every level in herringbone or longitudinal patterns. Smoke spill ductwork rated 600 degrees Celsius / 120 minutes connects every level to a rooftop discharge. The ANPR and POS infrastructure is at every entry and exit. The concourse spaces include passenger amenity, taxi rank shelter and shuttle bus interchange, all with their own HVAC scope.

Refer the SBKJ Airport and Aviation HVAC Duct Guide for the airport-side detail including terminal interface, jet-fuel and aviation gas considerations, and integration with airside ground services.

EV charging carpark — the new HVAC frontier

The EV charging carpark is the fastest-growing HVAC subset in the Australian parking market and the most complex from a code compliance perspective. The combination of lithium-ion thermal runaway risk, hydrogen off-gas potential, charger heat load and segregated ventilation requirements creates an HVAC design problem that did not exist five years ago.

The operator landscape divides into destination charging (long-dwell, AC slow charging at hotels, commercial offices and shopping centres), highway fast charging (short-dwell, DC fast charging at service stations and roadside locations) and depot or fleet charging (corporate fleet, rideshare base, bus depot). The major Australian operators include Tesla Destination Charging (the largest by site count, integrated at hotels and commercial properties), Tesla Supercharger V3 and V4 (highway and roadside, 250 to 350 kW per port), Chargefox (Carsales-acquired, urban and highway), Evie Networks (highway and regional), NRMA EV (NRMA-operated, regional and metropolitan), JOLT (kerbside and shopping centre), ChargePoint Australia (commercial and workplace), Schneider Electric EV (commercial integration), Pulse BP (at BP service stations) and Ampol AmpCharge (at Ampol service stations).

The HVAC overlay starts with NFPA 855 lithium-ion battery installation requirements and AS/NZS 5139 Australian battery storage safety. The thermal runaway risk in a parked EV battery is fundamentally different from any other carpark fire hazard. A lithium-ion cell that fails by internal short circuit produces a self-sustaining exothermic reaction that releases hydrogen, hydrogen fluoride, carbon monoxide, oxygen and a wide range of organic combustion products. The reaction propagates from cell to cell within a battery pack over a timescale of minutes to hours, and the fire cannot be extinguished by conventional water sprinkler — it must be cooled below the cell propagation threshold and held there for the full duration of the reaction. Documented EV battery fires have continued for 8 to 24 hours after initial detection and have reignited multiple times after apparent extinction.

The HVAC response divides into normal-mode operation and thermal-runaway-mode operation. Normal mode handles the charger heat load — a 350 kW DC fast charger dissipates 5 to 15 kW of waste heat, and a 10-stall fast-charging hub can produce 100 to 250 kW of combined heat that must be extracted. Slow AC charging at 3 to 22 kW per port produces minimal heat per port but the dwell time is long, so the cumulative heat output at a destination charging site with dozens of slow ports can still be significant.

Thermal-runaway mode triggers on hydrogen detection (25 percent LEL threshold), hydrogen fluoride detection, carbon monoxide spike above the normal carpark threshold, or temperature spike at the battery enclosure. The HVAC switches to dedicated thermal-runaway extract — spark-resistant fans, IECEx Ex-d rated motors, 304 stainless extract ductwork to handle the corrosive off-gas — with the extract path routed to a rooftop discharge stack sized for the design thermal-runaway flow rate. The dedicated extract is segregated from the general carpark ventilation grid because contaminating the carpark exhaust with thermal-runaway products would propagate the hazard.

SBKJ recommends SBAL-V auto duct line with 304 stainless feed for the EV charging room and the dedicated thermal-runaway extract path. The SBSF-1525 spiral tubeformer fabricates the round duct connections at the spark-resistant extract fans. The SBFB-1500 spiral former handles larger diameter extract trunks. All fan motors in the thermal-runaway extract path are IECEx Ex-d rated with Zone 2 classification per AS/NZS 60079. Hydrogen, hydrogen fluoride, carbon monoxide and temperature sensors at the ceiling of every EV charging bay wire to the BMS for thermal-runaway logic activation.

Tesla Supercharger V3 and V4 canopies (250 to 350 kW DC per port) are typically outdoor installations under a weatherproof canopy. The canopy ventilation is minimal because the open-air environment handles the charger heat load by natural convection. The HVAC scope at a Supercharger site concentrates on the equipment building (transformers, switchgear, control electronics) and any user amenity (washroom, refreshment area). Refer the SBKJ EV Charging Hub and BESS HVAC Duct Guide for the dedicated EV charging hub detail.

Battery storage room (BESS) installations co-located with EV charging carparks — increasingly common for peak shaving, demand management and grid stabilisation — follow the dedicated BESS HVAC provisions. Refer the SBKJ EV Charging Hub and BESS HVAC Duct Guide for the BESS HVAC architecture.

Standby generator, switchroom and ancillary plant HVAC

Carparks with critical 24-hour operation — airport, hospital, premium hotel valet, ANPR data centre, EV charging hub — typically have a standby diesel generator sized to support the essential loads during mains power failure. The generator HVAC has specific requirements that intersect with the broader carpark ventilation design.

The generator radiator heat extract is sized to 100 percent of the generator rated output plus 30 percent safety margin. A 500 kVA generator dissipates approximately 250 to 400 kW of radiator heat at full load — significant ventilation airflow at the radiator face is required to maintain the radiator outlet temperature below the engine cooling threshold. SBKJ SBLR-600 longitudinal seam welder fabricates the heavy-gauge generator exhaust duct. 304 stainless steel is specified for the radiator coil exhaust path to extend service life against the high-temperature, moisture-laden exhaust stream.

The generator exhaust stack is classified Zone 2 per AS/NZS 60079 because the exhaust contains residual unburnt fuel vapour at start-up and shutdown. Spark-resistant fans and IECEx Ex-d rated motors are mandatory in any extract fan handling generator exhaust. The exhaust stack discharge elevation is set by AS 1668.2 to clear any nearby air intakes, occupied openings and adjoining building intakes.

The switchroom — housing the main switchboard, distribution boards, transfer switches and metering — requires forced ventilation to clear switchgear heat. AS 1668.2 typical rate is 2 to 4 ACH for normal operation, raised to 4 to 6 ACH during fault current dissipation. The switchroom is segregated from the general carpark ventilation grid for fire-rated separation.

The lift machine room (where applicable — many modern carparks use machine-room-less lifts that eliminate this space) requires forced ventilation to clear lift motor heat. AS 1668.2 typical rate is 2 to 4 ACH.

The mechanical and ventilation plant room houses the carpark supply and exhaust fans, the smoke-spill fans, the air handling units for the concourse and ancillary spaces, and the BMS controls. Access for maintenance and crane swap-out of fans at 15-year refurbishment cycle must be coordinated at design stage.

IT comms, ANPR backend and lift machine room — clean spaces

The carpark IT infrastructure has grown significantly in the last decade with the adoption of ANPR, integrated payment systems and BMS uplink to operator central monitoring. The IT comms room — housing the ANPR backend server, the payment gateway, the BMS controller and the network switch — is now a critical clean space in every modern carpark.

The IT comms room HVAC requirements are similar to a small data centre. Redundant cooling is typical (N+1 configuration — two cooling units sized so either can handle the design load alone), with the redundancy aligned to the criticality of the carpark operation. Airport, hospital and premium hotel valet carparks typically specify N+1 minimum and may specify 2N (full duplicate) for the highest-criticality applications. Suburban CBD parking typically specifies N (single cooling unit with monitored alarm) plus operator response procedures.

The ANPR backend server handles the cardholder data flow from the POS terminals to the payment processor, the vehicle registration data flow from the ANPR cameras to the operator database, the customer record management, the reporting and analytics, and the BMS uplink. The Privacy Act 1988 and the Australian Privacy Principles govern the personal information handling, and the Payment Card Industry Data Security Standard (PCI DSS) governs the cardholder data handling. Physical security of the server room and audit access logging are PCI DSS and Privacy Act compliance requirements that intersect with the HVAC design — segregated room access, monitored entry, dedicated cooling.

The lift machine room — where present in lifts with traditional traction motor configurations rather than machine-room-less designs — houses the lift motor, the controller, the brake and the safety equipment. AS 1668.2 forced ventilation at 2 to 4 ACH clears motor heat.

The carwash and vacuum bay — where the carpark integrates a carwash service, common in shopping centre and airport parking — requires high-rate exhaust to clear water vapour, cleaning chemical aerosol and vacuum dust. AS 1668.2 typical rate is 8 to 15 ACH with 304 stainless extract duct because the chemical and moisture load rapidly corrodes galvanised duct.

The underground service yard — where the carpark interfaces with the loading dock, goods lift and waste compactor of the building above — has its own HVAC scope including diesel particulate extraction for delivery vehicles, waste compactor exhaust and dock-shelter conditioning.

Materials specification — galvanised, stainless, spark-resistant

Material selection in carpark HVAC follows a hierarchy driven by service environment, fire mode, coastal proximity and EV charging Li-ion exposure.

Galvanised G90 (Z275) carbon steel is the primary material for general carpark HVAC. The G90 designation refers to 0.90 ounces per square foot of zinc coating per side, equivalent to Z275 in metric (275 grams per square metre per side). G90 galvanised handles the typical carpark environment — vehicle exhaust, mild temperature range, occasional water ingress from ramps and entries — for the design life of the building. SBKJ SBAL-V auto duct lines run G90 galvanised at 0.6 to 1.5 millimetre thickness continuously and produce rectangular duct sections with TDF flange in a single pass.

304 stainless steel is specified for the EV charging room and EV bay dedicated extract, the Li-ion battery thermal runaway extract path, the carwash exhaust, the standby generator radiator coil exhaust, and the coastal exhaust trunks at sites within 5 kilometres of the marine atmosphere. The 304 grade provides corrosion resistance against marine chlorides, the lithium-ion battery off-gas (hydrogen fluoride is highly corrosive to galvanised), and the carwash chemical aerosol. SBKJ SBAL-V auto duct lines run 304 stainless with no tooling change from galvanised, just a stop-and-reload of the coil. Pricing is roughly 4 to 6 times galvanised G90 by mass but the duct lengths in 304 stainless are typically a small percentage of the total carpark ductwork mass.

316 stainless steel is specified for the most demanding coastal sites — direct beachfront exposure, sites with significant chloride aerosol from cooling tower drift, and marine industrial environments. The 316 grade adds molybdenum for enhanced chloride resistance.

Spiral round duct fabricated on the SBKJ SBSF-1525 spiral tubeformer and the SBFB-1500 spiral former handles the round duct connections at jet fans, the tall multi-storey return risers, and any service area requiring round-section ductwork. Spiral round duct has the lowest static pressure loss per unit length of any duct geometry, and the spiral lock seam is inherently tight without separate site sealing.

Large rectangular smoke spill duct at 1,500 to 2,000 millimetre width is fabricated on the SBKJ SBTF-2020 auto duct line. The SBTF-2020 handles the largest rectangular section in the SBKJ portfolio and is specifically suited to the primary smoke spill main duct from basement fire zones to rooftop discharge.

Plasma-cut tap-ins and access panels are fabricated on the SBKJ SBPC1500 plasma cutter. The plasma cutter handles 1,500 millimetre wide sheet at full thickness range and produces clean cuts for bespoke transitions, access panels, fire damper frames and tap-in connections.

Stitchwelded jet fan housings are fabricated on the SBKJ SB-ZF1500 stitchwelder. The stitchweld is the preferred jet fan housing seam because it produces a tight pressure-rated joint with minimal heat distortion. The SB-ZF1500 handles housings up to 1,500 millimetre overall dimension.

Heavy-gauge generator exhaust duct is fabricated on the SBKJ SBLR-600 longitudinal seam welder. The SBLR-600 produces continuous longitudinal seams in heavy-gauge stainless or aluminised steel for high-temperature, high-pressure exhaust paths.

Spark-resistant fans and IECEx Ex-d rated motors are mandatory in any extract path classified hazardous: EV charging Li-ion thermal-runaway extract (Zone 2 H2), standby generator exhaust (Zone 2 fuel vapour), LPG taxi and forklift bay extract (Zone 1 LPG). The spark-resistant fan impeller uses non-ferrous material (typically aluminium alloy) or coated steel to prevent ignition spark on impact. The Ex-d motor housing is flameproof rated to contain any internal arc within the motor envelope.

Australian regional context and SBKJ presence

SBKJ Group operates from Box Hill North VIC and supports mechanical contractors across all Australian states with installation supervision, operator training and ongoing technical support. See the Australia regional page for state-by-state coverage detail.

The Australian carpark project pipeline through 2030 is concentrated in three vectors. First, the new-build basement carpark embedded in mixed-use podium and residential tower developments — Lendlease, Mirvac, Crown Group, Frasers Property Australia, Multiplex (Brookfield), John Holland, Hutchinson Builders, Built (Lendlease), ICON Construction and Roberts Pizzarotti collectively deliver approximately 400 to 600 new basement carpark projects per year across the major capitals. Second, the EV charging carpark retrofit — installing dedicated EV charging bays in existing CBD commercial carparks, shopping centre carparks and destination hotel basements, with HVAC upgrade to NFPA 855 and AS/NZS 5139 thermal-runaway provisions. Third, the Park-and-Ride expansion at the state transit authorities — Sydney Metro stage 2, Melbourne Metro Tunnel station openings, Cross River Rail station carparks (Queensland Rail), the Mandurah Line extension (Transperth) and the Gawler Line electrification (Adelaide Metro) all add P&R carpark capacity at new and upgraded suburban stations through 2030.

ARBS 2026 — the Air Conditioning, Refrigeration and Building Services exhibition held in Sydney in May 2026 — is the principal Australian trade event for HVAC ductwork machinery procurement. SBKJ Group exhibits the SBAL-V auto duct line, the SBSF-1525 spiral tubeformer, the SBFB-1500 spiral former, the SBTF-2020 large rectangular auto duct line and the SBPC1500 plasma cutter at ARBS, with the spark-resistant fan and IECEx Ex-d motor specification highlighted for EV charging carpark applications.

FAQ — common questions on multi-storey, basement, automated, P&R and EV charging carpark HVAC

What does AS 1668.2 require for mechanical ventilation in an Australian basement carpark?

AS 1668.2 sets the minimum nominal ventilation rate for an enclosed carpark at 1 L/s/m² of floor area, which translates to approximately 6 air changes per hour at a typical 2.4 m ceiling height. The rate is raised to 2 to 5 L/s/m² in zones with diesel-truck dwell or where carbon monoxide and diesel particulate calculations exceed the workplace exposure standards. Modern Australian basement carparks almost always use carbon-monoxide-monitored demand-controlled ventilation — CO sensors at breathing height drive variable-speed jet fans (Aerolite, JetVent, Sanyo, Cyclonix) to maintain CO below 30 ppm 8-hour time-weighted average. SBKJ SBAL-V galvanised auto duct lines fabricate the main supply and exhaust risers, and SBFB-1500 spiral tubeformer handles the jet fan plenum connections.

How does an EV charging carpark differ from a conventional basement carpark for HVAC?

EV charging carparks add three HVAC overlays that do not exist in a conventional carpark. First, lithium-ion thermal runaway risk per NFPA 855 and AS/NZS 5139 requires spark-resistant fans, IECEx Ex-d rated motors and dedicated extract for hydrogen off-gas (1.25 percent of 25 percent LEL detection threshold) in the event of a vehicle battery cell venting. Second, charger heat load — a 350 kW DC fast charger dissipates 5 to 15 kW of waste heat that must be exhausted from the equipment enclosure or charger pad area. Third, the carbon monoxide and diesel particulate loadings drop as the fleet electrifies, but the modulating control logic must keep enough background ventilation to clear smoke from any vehicle fire including EV thermal runaway events that produce hydrogen, hydrogen fluoride and oxygen-rich combustion products. SBKJ recommends 304 stainless extract ductwork for EV charging rooms and dedicated extract bays, fabricated on the SBAL-V auto duct line.

What jet fan configuration is typical for an Australian multi-storey or basement carpark?

A typical 5,000 to 12,000 m² basement carpark in an Australian CBD uses a jet-fan ducted system rather than a fully-ducted ventilation grid. Supply air enters at one end of the carpark through a SBAL-V galvanised supply duct riser, jet fans (typically 200 to 450 mm diameter at 6 to 12 m/s discharge velocity) are arranged in a herringbone or longitudinal pattern through the carpark soffit to drive air across the parking bays, and exhaust risers at the opposite end extract via SBTF-2020 large-diameter spiral or rectangular duct. In fire mode under AS 1668.1, the jet fans switch to smoke-clearance direction at 6 air changes per hour with positive pressure on adjacent stair pressurisation. Jet fan housings are typically stitchwelded on the SBKJ SB-ZF1500 stitchwelder for tight pressure rating.

How does an automated parking system (APS) change carpark HVAC design?

An automated parking system (mechanical car stacker, pallet, conveyor) — used at Brisbane Casino Towers and several Sydney and Melbourne CBD residential developments — removes the human occupant from the parking bay envelope, which fundamentally changes the carbon monoxide and ventilation calculation. The engine is switched off at the entry vestibule before the vehicle is mechanised, so internal combustion CO loads collapse. But three new HVAC loads appear: the mechanical room and conveyor track must be ventilated for motor heat and lubricant vapours, the control room (often staffed) needs office-grade HVAC and ventilation, and the fire suppression strategy shifts from sprinkler-only to gaseous suppression (AS 4214) because water damage on pallets and conveyor would write off the entire stack. SBKJ recommends fully ducted SBAL-V galvanised supply and 304 stainless extract for the APS mechanical room, with SBFB-1500 spiral risers for conveyor track ventilation.

What materials should I specify for ductwork in a Park-and-Ride transit carpark?

Australian Park-and-Ride carparks at suburban train stations (Sydney Trains, Metro Trains Melbourne, Queensland Rail, Adelaide Metro, Transperth) are typically open-deck or partially enclosed multi-storey structures with high natural ventilation. The dominant material is galvanised G90 (Z275) per AS/NZS 4254 — fabricated on the SBKJ SBAL-V auto duct line — for the entry concourse climate-controlled spaces (ticketing kiosk, ANPR camera enclosure, POS terminal, restroom amenity). For coastal sites within 5 km of the marine atmosphere — common in Sydney, Brisbane and Perth station precincts — 304 or 316 stainless is specified for the exhaust trunk to extend service life. Jet fan housings remain galvanised but use the SBKJ SB-ZF1500 stitchwelder for the pressure-rated housings, and large primary smoke spill ducts are typically SBTF-2020 rectangular at 2000 mm width.

Does NFPA 88A or AS 1668.1 govern smoke control in Australian carparks?

AS 1668.1 is the binding Australian Standard for fire and smoke control in carparks, with NFPA 88A and NFPA 92 referenced as technical sources for the underlying physics. AS 1668.1 requires the mechanical ventilation system to switch to smoke-clearance mode on fire detection — typically driving the jet fans in a defined direction to clear smoke from the fire-affected bay toward an emergency exhaust outlet — at a rate of approximately 6 air changes per hour with positive pressure differential maintained on adjacent stair pressurisation paths (50 Pa per AS 1668.1). Ductwork in smoke-spill paths is rated for 600 degrees Celsius for 120 minutes per AS 1530.4. SBKJ SBTF-2020 and SBFB-1500 spiral risers handle the large smoke spill ducts up to 2,000 mm width and 1,500 mm spiral diameter.

Which Australian commercial carpark operators specify the highest HVAC standards?

Wilson Parking is the largest operator by site count (over 350 sites across all Australian capitals), Secure Parking is the largest by revenue with large CBD towers, airport and hospital contracts, and Care Park and Q Park operate substantial CBD portfolios. Premium valet specifications come from Crown Casino Valet (Crown Resorts), The Star Sydney Valet (Star Entertainment ASX:SGR) and major hotel chains. Airport parking — Sydney Airport (ASX:SYD), Melbourne Airport (APAC), Brisbane Airport and Perth Airport — typically applies the highest carbon monoxide and diesel particulate monitoring density because dwell times are long and the parking structures are large multi-storey enclosures. Property developers Lendlease (ASX:LLC), Mirvac (ASX:MGR), Crown Group, Frasers Property Australia and Multiplex (Brookfield) typically integrate the carpark HVAC into the mixed-use podium specification at the structural design phase.

How fast can SBKJ deliver ductwork machinery for an Australian carpark project?

SBKJ Group ships HVAC ductwork machinery from the Box Hill North VIC office with typical lead times of 90 to 120 days for stocked SBAL-V auto duct line configurations, 100 to 130 days for SBSF-1525 spiral tubeformer and SBFB-1500 spiral former, and 120 to 150 days for the larger SBTF-2020 (2,000 mm rectangular) and SBPC1500 plasma cutter. The SBLR-600 longitudinal seam welder and SB-ZF1500 stitchwelder for jet fan housings are typically 100 to 130 days. For carpark projects coordinated with a multi-storey or mixed-use podium construction schedule, mechanical contractors typically order machinery 6 to 9 months ahead of the carpark ductwork installation window. SBKJ engineers attend site for installation supervision, operator training and first-article acceptance — particularly important for spark-resistant fan housings on EV charging carpark Li-ion thermal runaway extract.