Why public transport depot HVAC is its own discipline
A bus depot is one of the most demanding industrial ventilation projects in the Australian built environment. The fleet generates a diesel exhaust load that compresses a small-scale freight terminal into a single building footprint. The driver amenity block runs on commercial comfort cooling adjacent to combustion-grade extract systems. The wash bay introduces chloride and chemical mist that destroys galvanised steel within five years. The EV bus transition adds a battery energy storage room with NFPA 855 fire safety logic. The hydrogen fuel cell roll-out adds Zone 2 hazardous area classification under AS/NZS 60079. Every zone has its own air change rate, its own duct material specification, its own fire and smoke damper interface, and its own pathway to AS 1668.2 compliance. Doing it well requires the mechanical engineer to specify five or six different ductwork systems within one site and the duct fabricator to deliver them on a single procurement package.
Australian public transport depots in 2026 are at the centre of a once-in-a-generation transition. The contracted operators — Transdev across Sydney, Melbourne, Adelaide and Perth; Kinetic Group running the Skybus airport service, Brisbane Translink contracts, Adelaide Metro and significant Melbourne presence; CDC NSW operating 1,900-plus buses across Sydney, Newcastle and the Hunter; CDC Victoria across Sunbury, Tullamarine, Sandringham and Oakleigh; Brisbane Transport at the council-owned depots; ACT Transport Canberra and City Services at Tuggeranong, Belconnen and Woden; the Public Transport Authority of Western Australia in Perth; Adelaide Metro under the Department for Infrastructure and Transport SA; Metro Tasmania in Hobart, Launceston and Burnie; the Darwin Bus Service in the Northern Territory — are converting fleets from diesel to battery electric and in some cases to hydrogen fuel cell. New depots are being built to accommodate the charging infrastructure. Existing depots are being retrofitted to reduce diesel exhaust load and add EV charging zones in shared envelopes. The HVAC scope on every one of these projects is the load-bearing engineering specification.
This guide compiles the standards framework, the operator-specific requirements, the equipment selection logic for diesel exhaust capture, the BESS room design discipline for EV depots, the hydrogen fuel cell hazardous area rules, the wash bay material selection, the maintenance pit ventilation, the driver amenity HVAC, the control room redundancy, and the SBKJ machinery best suited to each zone. It is written from a Box Hill North Victoria engineering perspective for project teams across the Australian states and territories, with reference data and worked design points drawn from active depot projects and operator-side specifications.
Australian public transport operators in 2026 — who specifies what
Understanding the operator landscape is the first step in specifying depot HVAC because each operator imposes their own equipment standards, supplier accreditation requirements and lead-time expectations on the engineering procurement contractor. The duct fabricator who builds the operator catalogue into the quotation gets the next call.
Transdev Australia
Transdev operates contracted bus services across Sydney (Western Sydney Buses, Region 3), Melbourne (multiple regions under the Public Transport Victoria contract framework), Adelaide (Adelaide Metro contract) and Perth (transition contracts). The Australian operation sits under the Transdev Group umbrella with local management based in Sydney. Transdev depot specifications emphasise AS 1668.2 compliance, demand-controlled ventilation with continuous CO and NO2 monitoring, full integration of overhead diesel exhaust capture (Plymovent or Nederman are the typical specified brands), and detailed asset documentation under their internal fleet management system.
Kinetic Group
Kinetic Group is one of the largest bus operators in Australia and New Zealand, holding contracts including the Skybus Melbourne airport shuttle, Brisbane Translink franchise operations, Adelaide Metro contracts and substantial Sydney metropolitan presence. The group has been expanding through acquisition and its depot specifications reflect a mixed inheritance — older diesel-focused depots with retrofit overhead capture systems alongside newer hybrid and EV-ready depots with integrated BESS provisioning. Kinetic Group depot HVAC specifications increasingly require dual-fuel readiness: diesel exhaust capture at existing bays and EV charger pads with electrical and BESS provision at adjacent bays in the same building envelope.
CDC NSW and CDC Victoria
CDC operates as ComfortDelGro Cabcharge across NSW and Victoria. CDC NSW runs 1,900-plus buses across Sydney, Newcastle and the Hunter region from depots including Hillsdale, Rockdale, Belrose, Kogarah and the Hunter facilities. CDC Victoria operates Melbourne metropolitan routes from Sunbury, Tullamarine, Sandringham and Oakleigh depots. The CDC engineering team specifies AS 1668.2 ventilation rates with a focus on energy efficiency — demand-controlled ventilation, heat recovery on extract systems where feasible, and free cooling cycles during temperate seasons. CDC depots have been early adopters of overhead diesel exhaust capture at all bays.
Translink Queensland and Brisbane Transport
Translink is the Queensland government brand for public transport across South-East Queensland, with operations contracted to multiple providers including Brisbane Transport (council-owned), Kinetic Group, Transit Australia Group and others. Brisbane Transport operates the council depots including Eagle Farm, Sherwood and Toowong, running an extensive diesel fleet with progressive EV transition under the council's zero-emission target. Translink's specification framework references AS 1668.2, the Queensland Building Code, and the Department of Transport and Main Roads engineering standards.
ACT Transport Canberra and City Services
Transport Canberra operates depots at Tuggeranong, Belconnen, Woden and supporting facilities, plus the Mitchell light rail depot. The ACT has been an early adopter of zero-emission buses with battery electric and hydrogen fuel cell trials in service. Transport Canberra depot HVAC specifications cover both legacy diesel zones and new EV charging yards with the hydrogen trial creating a localised Zone 2 hazardous area requirement at the refuelling point.
Public Transport Authority of Western Australia
The PTA WA operates bus services across the Perth metropolitan area through its Transperth brand, with depots at Beechboro, Karrinyup, Malaga, Welshpool and supporting facilities. WA depot specifications reflect the climate — high summer temperatures requiring elevated cooling load on driver amenities and control rooms, and the inland sites within the dry-continental zone where evaporative cooling supplements traditional refrigerant systems.
Adelaide Metro
Adelaide Metro operates under the South Australian Department for Infrastructure and Transport, with bus services contracted to Torrens Transit, Light City Buses, Kinetic Group and others operating from depots at Newton, Lonsdale, Mile End and Smithfield. Adelaide's coastal depots within 5 km of the Gulf St Vincent face elevated chloride loading on duct materials, pushing material specification toward 316L stainless on extract systems.
Metro Tasmania
Metro Tasmania operates depots at Hobart (Mornington), Launceston and Burnie, with a fleet transitioning from diesel to battery electric. The depots are smaller than the mainland metropolitan operations and the HVAC scope is correspondingly more compact, but the principles of source capture, BESS room separation and driver amenity comfort are identical.
Darwin Bus Service and Northern Territory operations
The Northern Territory operates a smaller bus network with the Darwin Bus Service and supporting regional routes. The tropical climate creates a humidity load on duct condensate management that is the dominant design challenge — wet season relative humidity above 80 percent for extended periods, requiring dehumidification in all enclosed driver areas and careful condensate handling on any cooled duct surfaces.
Yarra Trams (KDR Victoria)
Yarra Trams is operated by Keolis Downer (KDR Victoria) under contract to the Victorian Government, running the Melbourne tram network from depots at Preston, Brunswick, Glenhuntly, Camberwell, Essendon and Kew. The tram workshops have a different HVAC profile from bus depots — no diesel exhaust load, but heavy welding fume, paint extract, abrasive blast booth and overhead crane bay ventilation. Tram depots are typically older buildings with high-ceiling workshop bays and the ductwork retrofit work is substantial.
Long-haul and coach operators
Premier Stagelines (the Stagecoach Melbourne operation), Westside Bus Co, Murrays Coaches (Sydney and Canberra headquartered, operating major coach terminal infrastructure), Greyhound Australia (the long-haul coach operator with depots and terminal facilities across the East Coast), BusBiz and Buswest as the regional Western Australian operators, and Express Buslines on the Sydney-Newcastle corridor all run coach terminals with a different HVAC profile from urban bus depots — fewer parked vehicles, longer dwell times, integrated passenger waiting areas and ticketing offices.
Bus body builders
Volgren Australia (Geelong main plant plus Brisbane facility), Custom Bus Group (Melbourne and Sydney), Bustech (Brisbane and Adelaide), Mills-Tui (Brisbane), and Foton Mobility Australia (Maleny QLD assembly for electric buses) are the major Australian bus body builders. Their workshops combine chassis paint booths, body welding, fibreglass repair, electrical assembly and final inspection — HVAC scope spanning the full automotive paint booth specification through to driver amenity HVAC. The duct fabricator who supplies bus body builders gets a different mix of work from the depot operator — more paint booth, more abrasive blast, more weld extract.
Standards framework for Australian bus depot HVAC
The Australian standards stack for a bus depot is layered across mechanical ventilation, fire and smoke control, hazardous area classification and worker exposure limits. The duct fabricator works to AS/NZS 4254 for construction tolerances, but the design intent flows from a much broader code framework.
AS 1668.2 — Mechanical ventilation in buildings
The dominant standard for depot ventilation. Section 4 addresses industrial vehicle workshops, including the dwell parking zone and the active workshop bays. The baseline ventilation rate is 6 air changes per hour during routine dwell with parked vehicles. During the start-up sequence, when multiple buses idle simultaneously to warm up before service departure, the rate rises to 12 ACH. Demand-controlled ventilation tied to CO and NO2 sensors is the modern preference — the system runs at the minimum required rate during quiet periods and ramps up automatically when the sensor reading approaches the trigger threshold.
AS 1668.1 — Fire and smoke control
Covers the integration of HVAC with the fire safety system. Smoke management dampers at zone boundaries, smoke spill exhaust where required, fire-rated penetrations and the interlocks between fire detection and HVAC shutdown. Bus depots typically require smoke management when the indoor parking zone exceeds 2,000 square metres, with smoke spill capacity calculated against the fire load of a single bus.
AS 4254 — Ductwork for air-handling systems in buildings
The construction standard for the ductwork itself. Covers metal gauge selection by pressure class, joint and seam construction, sealing class (A, B, C), reinforcement, hanger spacing and pressure testing. The SBAL-V auto duct line fabricates to AS 4254 Class C with continuous longitudinal seams and TDF or angle flange joints, with the SBTF spiral tubeformer producing spiral-seamed round duct to the same class.
AS 1530.4 — Fire-rated penetrations
Covers the fire-rating of ductwork penetrations through fire-rated walls, floors and ceilings. Fire dampers, mortar collars, intumescent seals and tested penetration assemblies all reference AS 1530.4 fire resistance ratings. Bus depot fire dampers are typically rated FRL 120/120/120 at fire-rated wall penetrations.
NFPA 88A — Parking structures
The United States NFPA standard for parking structures and commercial garages, widely referenced in Australian bus depot fire engineering reports. NFPA 88A sets minimum ventilation rates, smoke management requirements and fire suppression interlocks for parking facilities. Indoor bus depots adopt NFPA 88A principles even when AS 1668.2 is the formal compliance pathway.
NFPA 30A — Motor fuel dispensing
Applies if the depot has an onsite fuel station — common at older diesel depots and at coach terminals where buses refuel between services. NFPA 30A covers the dispensing area as a hazardous location with electrical equipment ratings and ventilation requirements that exceed general depot requirements.
NFPA 855 — Stationary energy storage systems
The dominant code for the BESS room at an EV bus charging yard. NFPA 855 Chapter 9 covers explosion control and Chapter 14 covers lithium-ion specific requirements including gas detection, rapid HVAC shutdown logic, fire-rated separation and deflagration vent pathways. Australian EV bus depots typically reference NFPA 855 in conjunction with AS/NZS 5139 (battery storage equipment up to 200 kWh) and AS 1668.2 (mechanical ventilation of the surrounding building).
AS/NZS 5139 — Battery storage equipment
The Australian and New Zealand standard for battery storage equipment up to 200 kWh. Section 5.4 references ventilation requirements, Section 6 covers mounting and installation, and Section 9 covers fire safety. For utility-scale BESS the dominant standards are NFPA 855 and IEC 62933, with AS/NZS 5139 supplementary.
AS/NZS 60079 — Hazardous area classification
Covers the classification of areas with potential flammable atmospheres. Critical for depots with fuel stations (Zone 1 within the dispenser nozzle envelope, Zone 2 in the surrounding 3-metre radius) and for hydrogen fuel cell refuelling (Zone 2 within 3 metres of the refuelling nozzle, with gas accumulation areas at high level potentially classified Zone 1). All electrical equipment including HVAC fans within a classified zone must be ATEX or IECEx certified to the appropriate gas group and temperature class.
AS 1940 — Flammable liquid storage
Applies to bulk diesel storage at depots with onsite refuelling. Specifies tank construction, bunding, ventilation and separation distances. The HVAC interface is at the fuel storage room ventilation and any forced exhaust from a bunded enclosure.
AS 2865 — Confined spaces
Applies to maintenance pits, fuel tank inspection chambers and any enclosed space that workers enter. The HVAC interface is the forced ventilation system that brings the confined space into safe oxygen, flammable gas and toxic gas concentration ranges before entry.
AS 3000 — Electrical installations (the Wiring Rules)
Covers the electrical installation including the HVAC plant electrical supply, motor protection, RCD protection and the interlocks between fire detection and HVAC shutdown. The duct fabricator does not work directly to AS 3000 but the depot HVAC system integration depends on AS 3000 compliance for the controls.
AS 1851 — Maintenance of fire protection systems and equipment
Sets the annual testing schedule for fire dampers, smoke dampers, smoke management fans and the supporting HVAC fire safety equipment. The depot operator inherits the AS 1851 schedule from the building commissioning.
ASHRAE Applications Handbook Chapter 16 — Parking facilities
The international reference for parking garage ventilation, including bus depots. ASHRAE Chapter 16 covers ventilation rate calculation, CO and NO2 sensor placement, fan selection and smoke management. Often referenced in Australian engineering reports as a supporting design framework alongside AS 1668.2.
AS 5601 — Gas installations
Applies if the depot uses compressed natural gas (CNG) for vehicle fuel or for facility services. CNG bus depots have specific ventilation requirements for the dispenser area, the gas storage room and the maintenance bays where CNG buses are serviced.
AS 4031 — Transportation noise
Covers noise from transportation infrastructure including bus depots. The HVAC interface is the boundary noise from ventilation fans and the internal noise inside driver amenity areas. Fan selection, duct silencer specification and structural isolation all feed back to AS 4031 compliance.
Safe Work Australia Workplace Exposure Standards (WES)
The legally enforceable airborne contaminant limits for Australian workplaces. The critical values for bus depots are diesel particulate matter (elemental carbon) at 0.1 mg per cubic metre time-weighted average over 8 hours, carbon monoxide at 30 ppm 8-hour TWA, nitrogen dioxide at 5 ppm short-term exposure limit (STEL) over 15 minutes, and formaldehyde at 1 ppm STEL where formaldehyde may be present (cleaning chemicals, fibreglass repair).
AS 3580 — Ambient air quality boundary monitoring
The standard for ambient air quality monitoring at the boundary of an industrial site. Bus depots near sensitive receptors (residential, schools, hospitals) may be required to monitor boundary nitrogen dioxide, particulate matter and odour to demonstrate AS 3580 compliance under the project planning conditions.
Diesel exhaust capture systems — the heart of a bus depot HVAC design
A diesel bus depot lives or dies on its source capture system. Without source capture the general ventilation rate must be high enough to dilute exhaust emissions from up to 50 buses idling simultaneously during start-up — an impractical air change rate of 30-plus per hour in many depots. With source capture, each bus is connected to a flexible exhaust hose before the engine starts, and 80 to 95 percent of the combustion products are extracted at source before they mix with the general air. The general ventilation rate then reduces to AS 1668.2 minimums of 6 to 12 ACH, the fan power drops, the heating and cooling load on make-up air collapses, and the depot becomes commercially viable to operate.
Five OEMs dominate the Australian diesel exhaust capture market:
Plymovent
The Netherlands-based brand with extensive Australian installations. Plymovent's overhead rail system supports a flexible exhaust hose that clips onto the bus tailpipe before the engine starts. The hose tracks along the rail as the bus pulls forward and disconnects at a release point at the door of the bay. Plymovent systems are specified at Transdev, Kinetic and Brisbane Transport depots, among others. The duct fabricator scope is the steel header serving each rail, the connection to the main extract trunk, and the general HVAC supply and return — Plymovent supplies the rail, hoses and the dedicated fan package.
Nederman
The Swedish multinational with a strong industrial heritage. Nederman supplies similar overhead rail systems with a focus on industrial-grade construction. Nederman is specified at several CDC NSW depots and at Volgren and Custom Bus body shops where the system handles both vehicle exhaust and welding fume extraction with the same rail.
AirVac
An Australian-headquartered supplier with significant depot installations across the eastern states. AirVac systems are commonly used at smaller and mid-scale depots where the order volume does not justify a Plymovent or Nederman direct engagement.
Aercology
The United States brand specialising in source capture and air filtration. Aercology systems are found at Australian depots through engineering procurement contractor specifications, particularly on retrofit projects where the source capture system is replacing an older general dilution approach.
Eurovac
A North American manufacturer with stationary and mobile source capture solutions. Eurovac systems appear at Australian depots through partnership distribution arrangements.
Engineering the duct header for an exhaust capture system
The duct header serving the overhead rail is sized for the cumulative air volume of all bays connected to it. A typical single-bay exhaust hose handles 2 to 4 cubic metres per second at a duct velocity of 12 to 18 metres per second. For a 10-bay rail running with all bays in use during start-up sequence, the header handles 20 to 40 cubic metres per second at the main collection point. The header tapers down toward the upstream end of the rail as each branch tap reduces the flow requirement on the remaining run.
Duct material is galvanised G90 (Z275) baseline for the header. The exhaust gas temperature at the hose entry is typically 200 to 400 degrees Celsius for a diesel bus idling, but the gas dilutes rapidly with ambient air drawn through the hose connection and the duct surface temperature stays below 60 degrees Celsius. Galvanised G90 is therefore appropriate, with stainless variants considered only where the depot has elevated corrosion risk (coastal proximity, recycled wash water sharing the building envelope).
Duct gauge follows AS 4254 for the pressure class. Capture system fans operate at static pressures of 1,500 to 3,000 Pa, placing the duct in the medium-pressure range. SBKJ SBAL-V auto duct lines run galvanised G90 from 0.8 to 1.5 mm gauge with TDF flange or angle flange joints, hitting the AS 4254 Class C specification with continuous longitudinal seams.
Cleanouts every 3 to 4 metres of horizontal run allow periodic removal of accumulated particulate. The exhaust hose itself captures the bulk of the soot at the tailpipe, but fine particulate carries through to the duct and accumulates over months of operation. Cleanout access ports with bolted gasketed covers are specified during fabrication and not added later.
General dilution ventilation — what AS 1668.2 actually requires
Even with a source capture system at every bay, the depot needs general dilution ventilation to handle residual emissions from unconnected vehicles (a bus that has just pulled into a bay before the hose is connected, or a bus that has just released the hose to depart), to handle ambient infiltration through doors, and to maintain comfort and air quality across the broader floor space.
The AS 1668.2 calculation starts from the building volume and the ventilation rate per Section 4. For a 4,000 square metre indoor depot with 6 metre clearance, the building volume is 24,000 cubic metres. At 6 ACH dwell rate the air volume is 40 cubic metres per second supply, with matched extract. At the 12 ACH start-up rate the air volume rises to 80 cubic metres per second.
The system is typically built around two-speed or variable-speed fans on the supply and extract sides, with the speed driven by CO and NO2 sensor readings. The sensors trigger the high-speed mode when CO exceeds 25 ppm or NO2 exceeds 5 ppm STEL. Modern installations use four or six sensor zones across the depot floor with the highest-reading sensor dictating the global fan speed.
Supply air is typically delivered at high level through ceiling-mounted diffusers or perforated supply ducts, with extract at low level above the bus parking bays where the warm exhaust-laden air collects. The thermodynamic driver is the buoyancy of warm exhaust gas — drawing it from low level near its source rather than high level at the ceiling cuts the ventilation rate required to achieve the same contaminant concentration target.
Make-up air conditioning is the dominant energy cost. In Sydney, Melbourne, Brisbane and Adelaide the make-up air requires heating in winter and cooling in summer, with the cooling load dominant for depots above 30 degrees latitude during the December-to-February period. Heat recovery on the extract air is technically feasible but commercially marginal — the extract air carries combustion particulate that fouls heat exchangers within months. Some depots install a particulate filter upstream of a heat recovery wheel; most accept the energy penalty of fresh-air ventilation without recovery.
Demand-controlled ventilation with CO and NO2 sensors
The AS 1668.2 Section 4 framework permits demand-controlled ventilation (DCV) as an alternative to fixed-rate ventilation. The DCV system runs at the minimum rate required for ambient infiltration and cleaning when the depot is quiet, and ramps up to the full design rate when sensors detect elevated CO or NO2.
Sensor selection is critical. Electrochemical CO sensors with 5-year operating life are standard, mounted at 1.5 metres above floor level (operator breathing zone) and at the centre of each ventilation zone. NO2 sensors use electrochemical or chemiluminescence technology with 2 to 5 year operating life. Calibration is annual under AS 1851 for fire-safety related sensors and recommended at 6-month intervals for ventilation control sensors.
Sensor placement is engineered with the depot floor plan in mind. A four-sensor configuration places one sensor in each quadrant of the indoor parking area at 1.5 metre height. A six-sensor configuration adds sensors at the high-throughput bays near the depot exit doors where idling vehicles dwell longest. The control logic uses the highest sensor reading to drive the fan speed, with a 1-minute averaging window to avoid nuisance ramping on transient peaks.
Setpoints follow Safe Work Australia WES. CO at 25 ppm triggers the 12 ACH high-speed mode (the WES is 30 ppm TWA, so 25 ppm provides a margin). NO2 at 3 ppm triggers high-speed (the WES is 5 ppm STEL, so 3 ppm provides margin). The system reverts to low speed after 10 minutes of all sensors below the threshold.
Hysteresis between the trigger and revert thresholds prevents rapid cycling of the fans. A 5 ppm CO and 1 ppm NO2 hysteresis is typical. Fan ramp rates are limited to 10 percent per second on starting and 5 percent per second on slowing to avoid mechanical shock and noise spikes.
EV bus charging yards — the BESS-anchored architecture
The transition from diesel to battery electric buses changes the depot HVAC scope substantially. The headline saving is the diesel exhaust load — gone. The headline addition is the BESS room and the supporting electrical infrastructure that supports a depot full of 350 kW DC fast chargers running 30 to 80 buses overnight.
The charging yard load profile
A typical Australian EV bus depot in 2026 has 30 to 80 buses, each requiring 250 to 350 kWh of charge per night. Charging is concentrated in the 9-hour overnight window (typically 22:00 to 07:00) to take advantage of off-peak electricity tariffs and to align with bus service hours. At 80 buses each drawing 150 kW for 5 hours, the depot draws 12 MW continuous for the overnight window with peaks during the early evening when the first buses return.
This load is too large for most grid connections without either a substantial network upgrade or a behind-the-meter BESS that absorbs the grid connection point at a lower kW value and discharges to the chargers during peak charging hours. A 4 MWh BESS at the typical depot pulls the grid connection from 12 MW to 6 MW — halving the network upgrade cost and making the depot commercially viable on its existing supply.
BESS room HVAC architecture
The BESS room is a mechanically and electrically separated zone within the depot envelope. NFPA 855 Chapter 9 (explosion control), Chapter 14 (lithium-ion specifics) and AS/NZS 5139 (where capacity is under 200 kWh) govern the design. AS 1668.2 covers the ventilation of the surrounding building.
The container BESS arrives with integrated thermal management from the OEM — typically Tesla Megapack, Sungrow ST-series, Fluence Gridstack or Wartsila Quantum for the 1 to 4 MWh class. The container HVAC is supplied with the container and operates independently of the depot HVAC. Trying to substitute non-OEM HVAC into the container is technically and commercially impossible — the thermal management is engineering-tied to the cell chemistry and the warranty conditions.
The duct fabricator scope is the surrounding facility HVAC: the BESS control room (typically a 20 to 50 square metre annex with the site controller, communications equipment and protection relays), any walk-in switchgear building (housing the AC and DC switchgear, the inverter modules and the protection systems), the substation if dedicated to the depot, and the make-up air to the BESS room enclosure for fire suppression purge and gas detection clearance.
Gas detection in the BESS room covers hydrogen fluoride, hydrogen, carbon monoxide, carbon dioxide and the lower explosive limit (LEL). Sensors are positioned at high points where flammable gases stratify upward as they heat. On detection the BESS HVAC shuts down rapidly to prevent flammable gas circulation, and the depot general HVAC continues operating to provide make-up air to the BESS room for purge purposes if the fire engineer's plan requires it.
Smoke management for the BESS room follows the project fire engineering report. Smoke spill exhaust may be ducted through aluminised steel to handle elevated temperatures during a thermal runaway event. Smoke dampers at zone boundaries close on fire detection. The depot HVAC system is interlocked with the fire alarm to shut down at zones outside the BESS room while the smoke management system at the BESS room exhausts the products of combustion.
Charger pad ventilation
The chargers themselves are typically located outdoors at the bus parking bay or under a canopy. Charger cooling is internal to the cabinet (closed-loop glycol with a top-mounted heat exchanger), but the surrounding area may require supplementary ventilation in covered or indoor configurations. For an indoor charger pad inside a converted diesel depot bay, ventilation rate is calculated from the charger waste heat and the ambient design condition. A 350 kW charger dissipates 5 to 15 kW of waste heat at peak load.
Switchroom HVAC
The depot switchroom houses the transformers, the main switchgear and the charger feeders. Thermal load is dominated by transformer losses (typically 0.5 to 1 percent of transformer rating, so 50 to 100 kW for a 10 MVA depot transformer) plus switchgear losses. AS 1668.2 ventilation rates apply, with elevated rates if the room contains arc-flash-vulnerable equipment.
Ducted supply and return are conventional galvanised G90. The room operates at 24 to 28 degrees Celsius year-round with humidity below 70 percent relative humidity to avoid condensation on bus bars. Free cooling is used during cool weather to reduce energy cost.
Hydrogen fuel cell bus depots — Zone 2 hazardous area discipline
Hydrogen fuel cell buses are operating in Australian trials and limited service through 2026. Transport Canberra runs a hydrogen trial, Translink Queensland has several sites with hydrogen-ready infrastructure, and Foton Mobility Australia assembles hydrogen-electric chassis at Maleny QLD. The depot HVAC implications of hydrogen are substantial because hydrogen has a wide flammable range in air (4 to 75 percent by volume) and a very low minimum ignition energy.
Hazardous area classification
AS/NZS 60079.10.1 classifies the area around a hydrogen refuelling nozzle as Zone 2 — a place where an explosive gas atmosphere is not likely to occur in normal operation, but if it does occur will only persist for a short period. The Zone 2 envelope typically extends 3 metres horizontally from the nozzle and 1 metre vertically above the dispensing point. Above this zone, gas accumulation at the ceiling apex may be classified Zone 1 if the geometry does not allow rapid dispersion.
Within a Zone 2 envelope all electrical equipment including HVAC fans, lighting, sensors and motor starters must be ATEX or IECEx certified to the appropriate gas group (Group IIC for hydrogen) and temperature class (T1 for hydrogen ignition temperature). Fan motors are sealed and explosion-protected with EEx d or EEx e enclosures, sensors are intrinsically safe with EEx ia certification, and all cabling is rated for the zone.
Ventilation design for hydrogen handling
Inside an enclosed hydrogen handling area (the refuelling building, the hydrogen storage room, the gas distribution corridor) ventilation rates are 12 to 30 ACH continuous to prevent gas pocket accumulation. Hydrogen rises rapidly so high-level extract at the roof apex is mandatory, with low-level make-up air through louvres or ducted supply. The extract fans run continuously and have backup power for emergency operation.
Duct material is galvanised G90 with welded longitudinal seams to AS/NZS 4254 Class C. Continuous grounding bonds out any static charge that could ignite hydrogen at a duct seam. Aluminium ducting is avoided because of the elevated risk of frictional sparks on accidental contact.
Hydrogen detection
Hydrogen sensors at the ceiling apex and at the extract intake provide redundant detection of gas accumulation. On detection of 25 percent of the lower flammable limit (1 percent by volume hydrogen in air) the ventilation system ramps to full speed and the refuelling system isolates. At 50 percent LFL the entire system shuts down and the alarm raises.
Bus wash bays — chloride and chemical mist material specification
Bus wash bays are one of the most material-aggressive environments in the depot. The combination of recycled wash water (frequently with elevated chloride from cumulative cleaning chemical residues), brick-acid wheel cleaners (hydrochloric acid solution), chlorinated disinfectants and continuous moisture creates a corrosion environment that destroys galvanised G90 ductwork within 3 to 5 years.
Specify 304L stainless steel as the baseline for bus wash bay ductwork. For coastal depots within 5 km of marine atmosphere or for recycled-water wash systems with concentrated chlorides above 200 mg per litre, specify 316L stainless. Duct seams should be continuously welded or sealed to AS/NZS 4254 Class C minimum. Gaskets should be EPDM or chlorinated polyethylene rather than neoprene, which degrades under chlorinated chemical exposure.
The SBKJ SBAL-V auto duct line runs 304L and 316L stainless in the same envelope as galvanised, with quick coil changeover for mixed projects. Lock seam options include the pittsburgh and snaplock for stainless, with the snaplock providing tighter sealing for the higher moisture environment.
Wash bay ventilation rate is 8 to 10 ACH continuous during washing operations and 4 to 6 ACH during dwell. Supply air is delivered through ceiling diffusers at low velocity (3 to 4 metres per second face velocity at the diffuser) to avoid disturbing the wash spray pattern, with extract at the rim of the bay through a perforated low-level extract duct. The extract collects the chemical mist and chlorinated vapour before they migrate to the adjacent indoor parking area.
Make-up air conditioning is significant for indoor wash bays in cooler climates because the wash water and ambient evaporation generates significant cooling that the make-up air must overcome to maintain operator comfort. A wash bay operating in Melbourne in winter requires substantial heating on the make-up air supply.
Maintenance pit ventilation
Maintenance pits below the bus parking position give the technician access to the underside of the vehicle for engine work, transmission service, brake inspection and exhaust system repair. The pit is a confined space under AS 2865 and accumulates diesel fuel vapour, oil mist, brake dust and any exhaust products from a parked vehicle that ran into the bay.
Ventilation rate is 10 ACH minimum continuous, rising to 20 ACH when the bus engine is running for diagnostic work. Supply air is delivered at low level at the pit floor through a perforated supply duct running the length of the pit, with extract at the rim of the pit through a perimeter slot or grille. A portable ventilation hose is connected to the tailpipe during any engine-running work.
Lighting in the pit must be intrinsically safe to AS/NZS 60079.10.1 Zone 2 because diesel vapour can accumulate during a fuel leak or during heavy idling work. All power outlets must be RCD-protected per AS 3000.
SBKJ ductwork for pit ventilation is conventional galvanised G90 in 1.0 to 1.2 mm gauge, sized for 4 to 8 metres per second velocity to keep noise below 55 dB(A) at the pit operator position per AS 4031. Stainless options are considered for depots with elevated cleaning chemical use in the pit.
Engine teardown and DPF service bays
Engine teardown bays handle diesel injector cleaning, DPF service, turbo replacement and other high-emission service work. The work generates combustion product release at intermediate temperatures and concentrations between idle exhaust and engine bay welding fume.
Local exhaust ventilation at the workbench captures fume at the source. Hood face velocity is 0.5 to 1.0 metres per second at the hood opening, with the hood positioned within 300 mm of the work surface. The extract duct runs to a particulate filter and HEPA stage before exhaust to atmosphere.
DPF cleaning operations involve high-temperature regeneration cycles that can release residual soot and partially combusted fuel. The extract system must handle a 200 to 400 degrees Celsius gas stream at the hood entry, falling to 60 degrees Celsius at the duct outlet after dilution with ambient air drawn through the hood face.
Galvanised G90 is acceptable for the duct at the hood entry because the gas dilutes rapidly. Stainless variants are considered for sites with frequent DPF service work where galvanised would wear faster.
Bus body workshop and paint booth
Bus body builders (Volgren, Custom Bus, Bustech, Mills-Tui, Foton Mobility) operate dedicated workshops with paint booths, abrasive blast cabins, fibreglass repair zones and electrical assembly bays. The HVAC scope spans the full automotive paint booth specification.
Paint booth ventilation
Downdraft paint booths for chassis primer, body colour and clearcoat operate to NFPA 33 Chapter 7 and AS 4114.2 with leaf-canopy velocity of 0.3 to 0.5 metres per second across the bus. A typical bus body booth at 100 square metres leaf-canopy area at 0.4 metres per second moves 40 cubic metres per second supply per booth. With three sequential booths (primer, basecoat, clearcoat) the total paint shop air handling load reaches 100 to 150 cubic metres per second.
Duct material is galvanised G90 for supply upstream of the booth and 304L stainless for waterborne basecoat exhaust where amine catalysts attack zinc. Bake oven exhaust at 180 to 200 degrees Celsius requires 304 or 309 stainless rated to NFPA 86. Spark-resistant fans on the exhaust side are mandatory under NFPA 33 Chapter 6. See the automotive paint booth HVAC duct guide for booth-specific specification.
Abrasive blast booth
Bus chassis surface preparation often involves abrasive blast cabins (grit blast, vapour blast or slurry blast). The dust load is heavy and the extract ducting requires careful design to maintain transport velocity above 18 metres per second in horizontal duct and 23 metres per second in vertical riser per NFPA 91. Spark-resistant construction throughout.
Fibreglass and composite repair
Bus body fibreglass repair and composite layup releases styrene vapour and dust during cutting. Local exhaust ventilation at the repair bay captures vapour at the work surface, ducted to an activated carbon adsorption stage before exhaust to atmosphere. See the composite manufacturing HVAC guide for detailed specification.
Driver amenity HVAC
The driver amenity block is a commercial comfort cooling zone within the depot envelope. Includes the break room, toilets, locker room, meal preparation area, training room and dispatch office. AS 1668.2 ventilation rates apply to the toilets and the break room, with comfort cooling sized to the occupancy.
Outside air rate is 8 to 12 litres per second per person in break rooms and offices, with full economiser cycle in temperate climates. Toilet exhaust is 25 litres per second per fixture per AS 1668.2 with continuous operation during working hours.
Duct material is galvanised G90 throughout the amenity block. Round duct from the SBKJ SBTF spiral tubeformer is commonly used in the break room and training room ceilings where the architectural intent favours visible spiral duct over concealed ceiling plenum.
Heating and cooling is typically provided by a packaged unit or a VRF system with multiple indoor units. Redundancy is N+1 for the dispatch control room and N for the break room.
Dispatch and operations control room HVAC
The dispatch control room operates 24/7 and supports the bus operations across the depot service area. Houses the dispatch consoles, the radio and SCADA equipment, the CCTV monitoring, and the operations supervisor. Thermal load is dominated by the monitoring equipment and the operator workstations — typically 5 to 15 kW for a small control room.
VRF or DX with N+1 redundancy on the HVAC plant is standard. Ducted supply to multiple workstations through high-induction diffusers, return air through ceiling plenum. Temperature setpoint 22 degrees Celsius plus or minus 2 degrees, humidity 40 to 60 percent relative humidity to maintain operator comfort and equipment reliability.
Free cooling is used overnight in cool seasons. The HVAC system is interlocked with the building fire alarm to shut down on fire detection, with smoke management providing pressurisation of the control room to maintain occupant safety during evacuation.
Vehicle wash plant — chlorinated chemical mist extract
A vehicle wash plant differs from the bus wash bay in scale and chemical intensity. Some depots operate dedicated wash plants with multiple bays handling 50 to 200 buses per night. The chemistry is more aggressive — concentrated brick acids, alkaline cleaners and chlorinated disinfectants — and the ventilation rate is higher to handle the cumulative chemical mist.
Specify 316L stainless ductwork for the wash plant supply and extract. Continuous welded seams to AS/NZS 4254 Class C. EPDM gaskets at all joints. Inlet and outlet plenums fabricated from 316L sheet with continuous welds. Air change rate 10 to 12 ACH continuous during washing operations.
The wash plant exhaust is typically discharged through an acid mist scrubber before atmospheric release, with the scrubber recirculating wash chemicals through a packed-bed contactor to capture the mist droplets and the dissolved chlorine.
Coach terminals — a different HVAC profile
Coach terminals (Greyhound Australia, Murrays Coaches, Premier Stagelines and the regional long-haul operators) have a different HVAC profile from urban bus depots. Fewer parked vehicles, longer dwell times, integrated passenger waiting areas and ticketing offices, and frequently retail and food co-location on the terminal site.
Coach parking apron
The coach parking apron is typically outdoor or semi-covered with no full enclosure. HVAC scope is the entry and exit roller doors if the coaches enter an enclosed maintenance bay, plus any covered passenger drop-off area where engine idling occurs.
Passenger waiting area
The passenger waiting area is a commercial comfort cooling zone with AS 1668.2 ventilation rates for occupant density. Typical 10 litres per second per person outside air with cooling to 22 to 24 degrees Celsius. Integrated ticketing and retail HVAC piggybacks on the central plant.
Coach maintenance bay
The coach maintenance bay handles servicing, refuelling and overnight parking. HVAC follows the bus depot framework with source capture at active service bays and general dilution ventilation across the floor.
Tram workshop HVAC — Yarra Trams at Preston, Brunswick, Glenhuntly, Camberwell, Essendon and Kew
Yarra Trams (operated by KDR Victoria) maintains the Melbourne tram network from six depots: Preston (Z-class and articulated maintenance), Brunswick (B-class focus), Glenhuntly (E-class), Camberwell (C-class), Essendon (mixed) and Kew (heritage W-class restoration). The tram workshops have a different HVAC profile from bus depots — no diesel exhaust load, but heavy welding fume, paint extract, abrasive blast booth and overhead crane bay ventilation.
Welding fume extraction
Tram body welding (MIG, MAG and TIG) generates fume that must be captured at source per AS/NZS 1715. Local exhaust ventilation at each welding station with a movable hood positioned within 200 mm of the weld pool. Extract velocity 0.5 metres per second at the hood face. Duct material galvanised G90 with 304L stainless considered for stainless steel welding stations.
Tram paint shop
Tram paint shops operate to NFPA 33 and AS 4114.2 with downdraft booth velocity 0.3 to 0.5 metres per second. Tram livery painting requires extended booth length — Melbourne E-class trams are 33 metres long, requiring a paint booth of 35 to 40 metres internal length. Air handling load scales accordingly.
Overhead crane bay
Tram workshop overhead crane bays operate for lifting heavy body sections, bogies and traction motors. The crane bay extends the full workshop height (typically 15 metres) with HVAC distribution at multiple levels to handle the volume.
Heritage workshop (Kew)
The Kew depot handles heritage W-class tram restoration with traditional craft work including carpentry, leadlight glazing and brass polishing. HVAC for the heritage workshop focuses on dust extraction at woodworking stations and chemical extract at the leadlight bench.
Sydney Trains workshops and rail vehicle maintenance
Sydney Trains operates rail vehicle workshops at Newcastle (Cardiff) and Sydney (Sydenham, Mortdale, Flemington), with similar HVAC profiles to tram workshops but at larger scale for the suburban and regional fleet. The HVAC scope includes welding fume extraction, paint booth ventilation, abrasive blast booth, body workshop dust extraction and the driver amenity block.
Putting it together — SBKJ machinery for the bus depot project
The bus depot ductwork package requires a fabricator who can move between galvanised G90 supply trunks, 304L and 316L stainless wash bay ducting, aluminised steel smoke management exhaust and the high-pressure capture system headers. SBKJ machinery covers the full material mix in a single envelope, allowing the project duct shop to fabricate to the project specification without coil changeovers on the critical path.
SBAL-V auto duct line — the primary recommendation
The SBAL-V is SBKJ's flagship auto duct line, running at 16 metres per minute line speed with 87 kW total connected load. It fabricates rectangular ductwork in galvanised G90, 304L stainless, 316L stainless and aluminised steel up to 1.5 metre width and 1.5 mm thickness. The machine handles the general supply and extract trunks, the diesel exhaust capture duct headers, the wash bay stainless ductwork, and the BESS room dedicated HVAC duct. Quick coil changeover allows mixed-material projects to run through a single shift. For an Australian bus depot or coach terminal fit-out the SBAL-V is the primary specification.
See the SBAL-V product page for full specifications and the SBAL-V vs SBAL-III comparison for the leaner option.
SBAL-III auto duct line — the leaner option
The SBAL-III runs at 14 metres per minute with 15.7 kW connected load and the same material flexibility as the SBAL-V. For smaller depot retrofits or for body builder satellite operations the SBAL-III offers the same capability footprint at a lower power draw and lower floor area.
SBAL-II auto duct line
The SBAL-II at 18 metres per minute and 5.5 kW is the lightest auto duct line in the SBKJ range, suited to small-volume duct work production for tram workshop fit-outs and coach terminal retrofits where the production volume does not justify the full SBAL-V.
SBTF spiral tubeformer — round duct for amenities and waiting areas
The SBTF spiral tubeformer produces round duct from 80 mm to 1,500 mm diameter for ventilation runs in driver amenity blocks, training rooms, coach terminal waiting areas, dispatch control rooms and any architecturally visible duct location. Spiral seam construction reduces leakage to under 1 percent at 1,000 Pa for SMACNA leakage class 6. The SBTF range includes the 1500C, 1602 and 2020 configurations for different diameter and gauge ranges.
SBEM-1250 elbow machine
The SBEM-1250 produces round duct elbows up to 1,250 mm diameter, supporting the fittings package for any project running round trunk duct.
SBSF-1525 — square-to-round transitions
The SBSF-1525 at 2.5 kW produces transition fittings between square and round duct sections, handling the rectangular trunk to round branch transitions common in bus depot fit-outs.
SBFB-1500 flange forming machine
The SBFB-1500 at 7.5 kW and 1.20 metres per minute produces flanges for high-pressure duct connections, supporting the TDF and angle flange joints on the capture system headers.
SBHF and SBPC1500 — supporting equipment
The SBHF hydraulic folder and SBPC1500 plasma cutter support the duct shop's fitment work for transitions, takeoffs and project-specific custom pieces.
SBLR-600 and SBLR-600A — lockformers
The SBLR-600 and SBLR-600A lockformers at 7.6 metres per minute produce pittsburgh and snaplock seams for stainless steel wash bay ductwork and for any project where the auto duct line is supplemented by hand-formed pieces.
Material specification matrix for the Australian bus depot
The following matrix summarises the material specification across the typical depot zones, supporting the duct shop and the project mechanical engineer in their procurement planning.
Indoor parking and general dwell zone: Galvanised G90 (Z275) to AS/NZS 4254. SBAL-V or SBAL-III auto duct line. TDF or angle flange joints.
Diesel exhaust capture system header: Galvanised G90 (Z275) to AS/NZS 4254 Class C. SBAL-V auto duct line with reinforced gauge for the medium-pressure operation. Continuous longitudinal seams.
Bus wash bay supply and extract: 304L stainless to AS 1528. SBAL-V stainless variant. Continuous welded seams. EPDM gaskets.
Coastal depot wash bay or recycled water wash: 316L stainless to AS 1528. SBAL-V stainless variant with 316L coil. Continuous welded seams.
Maintenance pit ventilation: Galvanised G90 (Z275) in 1.0 to 1.2 mm gauge. SBAL-V or SBAL-III auto duct line.
Engine teardown bay local exhaust: Galvanised G90 baseline, 304L stainless for high-frequency service operations.
Paint booth supply: Galvanised G90 in 0.8 to 1.5 mm gauge. SBAL-V auto duct line with TDF flange.
Paint booth waterborne basecoat exhaust: 304L stainless in 1.2 to 2.0 mm gauge. SBAL-V stainless variant.
Paint booth bake oven exhaust: 304 or 309 stainless. SBAL-V stainless variant with high-temperature tooling.
Abrasive blast booth exhaust: Galvanised G90 in heavy gauge for the high-velocity transport. Spark-resistant construction.
BESS room dedicated HVAC supply and return: Galvanised G90 to AS/NZS 4254 Class C. SBAL-V auto duct line.
BESS room smoke management exhaust: Aluminised steel for elevated temperature operation during thermal runaway events.
Hydrogen fuel cell area ventilation: Galvanised G90 with welded longitudinal seams to AS/NZS 4254 Class C. Continuous grounding. SBAL-V auto duct line.
Driver amenity block supply and return: Galvanised G90. SBAL-III auto duct line. Round trunk runs through SBTF spiral tubeformer.
Dispatch control room HVAC: Galvanised G90 with N+1 redundancy on the plant. SBAL-V or SBAL-III auto duct line.
Tram workshop welding fume extraction: Galvanised G90 baseline, 304L stainless for stainless steel welding stations.
Tram workshop paint shop: Galvanised G90 supply, 304L stainless waterborne exhaust, 304 or 309 stainless bake oven exhaust.
Project timeline and lead time
A greenfield bus depot HVAC duct package typically runs 16 to 24 weeks from purchase order to commissioning of duct fabrication on site. The SBKJ machinery side of the lead time breaks down as follows:
SBAL-V auto duct line: 12 to 14 weeks for galvanised configuration, 14 to 16 weeks for stainless steel variants. Ocean freight 4 to 6 weeks to most Australian ports. On-site installation, mechanical commissioning and operator training by SBKJ engineers 1 to 2 weeks.
SBTF spiral tubeformer: 10 to 12 weeks. Ocean freight 4 to 6 weeks. Installation and commissioning 5 to 7 days.
SBAL-III or SBAL-II: 10 to 12 weeks for the leaner configurations.
Supporting equipment (SBEM, SBSF, SBFB, SBHF, SBPC, SBLR): 8 to 10 weeks individually, frequently shipped consolidated with the main duct line.
For brownfield retrofits where the duct shop is being upgraded as part of the project, the same machine timeline applies but the project critical path is usually civil and structural — confirm slab loadings, crane access and electrical supply 8 to 10 weeks before machine arrival.
Australian operators (Transdev, Kinetic, CDC NSW, CDC Victoria, Brisbane Transport, ACT TCCS, Adelaide Metro, PTA WA, Metro Tasmania, Yarra Trams) typically expect full Factory Acceptance Test documentation with the machine delivery, supporting their internal asset registers and insurance compliance.
Commissioning and air balancing
The commissioning sequence for a bus depot HVAC duct package follows the standard AABC or NEBB framework with depot-specific test points:
Static pressure verification at each duct branch confirming the design pressure drop against the actual installation. Discrepancies above 10 percent trigger investigation of duct construction defects, damper position errors or fitting selection issues.
Air volume measurement at every supply and extract grille with pitot traverse or vane anemometer. All booth supply branches within plus or minus 10 percent of design flow, exhaust within plus or minus 5 percent.
CO and NO2 sensor verification with calibrated gas mixtures confirming the demand-controlled ventilation trigger logic operates as designed. Sensor response time, hysteresis and fan ramp behaviour all verified.
Fire damper testing per AS 1851 confirming spring-loaded closure on fusible link release, latch operation and re-set capability.
Smoke damper testing confirming closure on smoke detector activation with the building fire alarm sequence.
Boundary noise survey per AS 4031 confirming fan and ductwork noise at the depot boundary fence does not exceed the planning approval limits.
Boundary air quality monitoring per AS 3580 where required by the project planning conditions, particularly for depots near sensitive receptors.
BESS room gas detection commissioning for EV bus charging yards confirming hydrogen fluoride, hydrogen, CO and LEL sensor calibration, alarm thresholds and HVAC shutdown logic per NFPA 855 Chapter 14.
Maintenance and ongoing operations
The maintenance schedule for a bus depot HVAC duct system blends conventional commercial HVAC maintenance with the safety-critical inspections specific to the bus depot environment.
Monthly: Visual inspection of capture system hoses for damage, capture system header cleanout access, CO and NO2 sensor reading verification against handheld instruments, fan vibration spot-check.
Quarterly: Filter replacement on supply air, demand-controlled ventilation calibration verification, fire damper visual inspection, smoke damper test cycle, wash bay duct inspection for chloride pitting.
Semi-annual: CO and NO2 sensor recalibration with gas reference, fan motor inspection, paint booth filter and arrestance media replacement, BESS room gas detection calibration.
Annual: Full AS 1851 fire damper testing, smoke damper testing, boundary noise survey, AS 3580 boundary air quality monitoring where required, full system pressure test.
Five-year: Duct internal inspection for chloride pitting, particulate accumulation, seam integrity. Major fan service. Filter housing structural inspection.
Frequently asked questions
What ventilation rate does AS 1668.2 require for a bus depot?
AS 1668.2 Section 4 covers industrial vehicle workshops and parking. The baseline for a diesel bus depot is 6 air changes per hour during routine dwell with parked vehicles, rising to 12 ACH during start-up sequences when multiple buses idle simultaneously to warm up before service. Demand-controlled ventilation tied to CO and NO2 sensors is the modern preference — CO setpoint at 25 ppm and NO2 at 5 ppm short-term exposure limit per Safe Work Australia WES. For a 4,000 square metre indoor depot with 6 metre clearance the design air volume during start-up is approximately 80 cubic metres per second supply with matched extract. EV bus depots reduce ventilation substantially because there is no combustion product, but the BESS room and switchgear room compensate with their own dedicated HVAC.
How does a diesel exhaust capture system like Plymovent integrate with depot HVAC?
Plymovent, Nederman, AirVac, Aercology and Eurovac all sell overhead rail systems with a flexible exhaust hose that clips onto the bus tailpipe before the engine starts. The hose retracts as the bus pulls forward and disconnects automatically at a release point. The captured exhaust enters a dedicated extraction main running the length of the bay, sized for 2 to 4 cubic metres per second per bus position at a duct velocity of 12 to 18 metres per second. The capture system removes the bulk of diesel particulate matter and combustion gases at source, reducing the general ventilation load. Best practice combines source capture at every bay with general dilution ventilation at 4 to 6 ACH for residual emissions and ambient air quality. SBKJ fabricates the supply trunks, return air mains, and any galvanised G90 capture duct headers — the proprietary overhead rail and hose hardware is supplied by the capture system OEM.
What HVAC materials should be specified for a bus wash bay?
Bus wash bays are wet, chlorinated, and frequently acidic from brick-acid wheel cleaners. Galvanised G90 will pit and red-rust within 3 to 5 years. Specify 304L stainless steel as the baseline and 316L stainless for high-chloride sites (coastal depots within 5 km of marine atmosphere, recycled water wash systems with concentrated chlorides). Duct seams should be continuously welded or sealed to AS/NZS 4254 Class C minimum and gaskets should be EPDM or chlorinated polyethylene rather than neoprene. The SBKJ SBAL-V auto duct line runs 304L and 316L stainless in the same envelope as galvanised, with quick coil-changeover for mixed projects.
What is required for an EV bus charging yard BESS room?
EV bus charging yards typically include a behind-the-meter BESS to flatten the grid demand profile during overnight depot charging when 30 to 80 buses may charge simultaneously at 150 to 350 kW each. The BESS room is governed by NFPA 855 Chapters 9 and 14 plus AS/NZS 5139 for systems up to 200 kWh and is mechanically separated from the rest of the depot by fire-rated walls. HVAC for the BESS room is dedicated, with rapid shutdown logic tied to hydrogen, carbon monoxide and lower-explosive-limit gas detection. The container BESS arrives with integrated thermal management from the OEM (Tesla Megapack, Sungrow, Fluence). SBKJ scope is the surrounding facility — control room, switchroom, electrical equipment building, driver amenities. Specify galvanised G90 for general supply and return, with aluminised steel on any smoke management exhaust path.
Do hydrogen fuel cell bus depots need special HVAC?
Yes. Hydrogen fuel cell buses operate at the Foton Mobility plant in Maleny QLD, in Transport Canberra trials, and at several Translink Queensland sites. The refuelling area is classified as a Zone 2 hazardous area under AS/NZS 60079.10.1 with a 3 metre release radius around the dispenser nozzle. Within the Zone 2 envelope all electrical equipment including HVAC fans must be ATEX or IECEx certified — explosion-protected motors, sealed bearings, no spark ignition sources. Ventilation rates inside any enclosed hydrogen handling area are typically 12 to 30 ACH continuous to prevent gas pocket accumulation. Hydrogen rises rapidly, so high-level extract at the roof apex is mandatory with low-level make-up air. SBKJ ductwork in these zones is fabricated from galvanised G90 with welded longitudinal seams to AS/NZS 4254 Class C and grounded continuously to bond out static charge.
What HVAC is required for a maintenance pit under a bus?
Maintenance pits are confined spaces under AS 2865 and accumulate diesel fuel vapour, oil mist, brake dust and any exhaust products from a parked vehicle that ran into the bay. Ventilation rate is 10 ACH minimum continuous, rising to 20 ACH when the bus engine is running for diagnostic work. Supply air is delivered at low level at the pit floor, extract at the rim of the pit, and a portable ventilation hose is connected to the tailpipe during engine-running work. Lighting in the pit must be intrinsically safe to AS/NZS 60079.10.1 Zone 2 because diesel vapour can accumulate, and all power outlets must be RCD-protected per AS 3000. SBKJ ductwork for pit ventilation is conventional galvanised G90 in 1.0 to 1.2 mm gauge, sized for 4 to 8 metres per second velocity to keep noise below 55 dB(A) at the pit operator position per AS 4031.
How do you specify ventilation for a bus body workshop paint booth?
Australian bus body builders (Volgren in Geelong and Brisbane, Custom Bus Group in Melbourne and Sydney, Bustech in Brisbane and Adelaide, Mills-Tui in Brisbane) operate downdraft paint booths for chassis primer, body colour and clearcoat. Booth ventilation follows NFPA 33 and AS 4114 with leaf-canopy velocity of 0.3 to 0.5 metres per second across the bus. A typical bus body booth at 100 square metres leaf-canopy area at 0.4 metres per second moves 40 cubic metres per second supply per booth. Materials are galvanised G90 for supply upstream of the booth and 304L stainless for waterborne basecoat exhaust where amine catalysts attack zinc. Spark-resistant fans on the exhaust side are mandatory under NFPA 33 Chapter 6. See the full automotive paint booth guide for booth-specific specification.
Which SBKJ machine is most suited to bus depot ductwork production?
For an Australian bus depot or coach terminal fit-out the SBAL-V auto duct line is the primary recommendation. It fabricates rectangular ductwork in galvanised G90, 304L stainless and 316L stainless up to 1.5 metre width and 1.5 mm thickness at 16 metres per minute line speed with 87 kW total connected load. The SBAL-V handles the general supply and extract trunks, the diesel exhaust capture duct headers, the wash bay stainless ductwork, and the BESS room dedicated HVAC duct. Round trunk runs in the driver amenity block and waiting areas are best served by the SBTF spiral tubeformer in 80 to 1500 mm diameter. For smaller depot retrofits the SBAL-III at 14 metres per minute and 15.7 kW is a leaner option with the same material flexibility. Both machines are exported from the SBKJ Australian headquarters with CIF, CFR or DDP terms and full Factory Acceptance Test documentation.
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