From a global perspective, buildings and construction account for around 37 percent of carbon dioxide (CO2) emissions.

In Australia, meanwhile, the transport sector contributes about a fifth of the nation’s CO₂ share.

Combined, these two sectors represent a huge opportunity for decarbonisation.

Whilst public transport and active travel are the most effective means of reducing emissions, road transport is here to stay in Australia. Fuel efficiency and use of alternate fuels are the most significant emission reduction opportunities.[i]

As a result, carpark fire safety design must evolve to accommodate what are currently considered by some as being ‘special hazards’.

A holistic, risk-based fire safety engineering approach is needed. So too is an agile building code framework that keeps pace with modern vehicles.

Contemporary carpark design

Carparks can be categorised as follows:

1. open-air (no roof),
2. open-deck (covered, but naturally ventilated by permanent openings in the façade),
3. enclosed (with limited or no permanent openings), and
4. basement (fully enclosed and sometimes beneath other building uses).

Expected fire scenarios differ in each type of carpark because of fundamental fire dynamics theory. This dictates that fire development and smoke movement are governed by carpark geometry and ventilation as well as fuel load.

Several factors could influence this, including:

• Low ceilings. Carparks often have low ceilings as developers look to maximise efficiency by keeping floor to floor heights to a minimum. Lower clearances over vehicles promote greater radiation feedback and faster fire development.
• Site constraints and architectural choices. Large, deep floorplates have greater potential fuel load (more vehicles). In addition, whilst carparks which have these large and deep floorplates may satisfy requirements for ‘open-deck’ carparks, they could have fire scenarios which do not behave as one may expect in smaller carparks that fit within this category. The reason for this is that the natural ventilation for open deck carparks is at the perimeter.
• Bigger and heavier vehicles. The anecdote that “parking spaces are getting smaller!” also has fire safety implications. Whilst standard parking bay sizes (2.4 m x 5.4 m as specified in AS 2890.1) have barely changed since the 1980s, vehicles have gotten larger and heavier. The upshot is that spacings between vehicles are getting smaller. This increases the likelihood of vehicle‑to‑vehicle fire spread.[ii]
• Co-location with storage. Within basements beneath other building occupancies (for example, apartments), parking spaces are frequently co‑located with storage. This may contain barbecues, battery chargers and light electric vehicles (LEVs) (also termed ‘electrically-assisted pedal cycles’, ‘personal mobility devices’, ‘e-bikes’ and the like). If these are within the same fire compartment as the carpark, additional fire hazards have been introduced which must be addressed. Statistically, LEVs are responsible for a significantly higher number of fires globally when compared to larger electric vehicles.[iii]
• Material selection and use. While carparks have traditionally been made from concrete and steel, designers in Europe and Australia are now exploring greater use of mass timber (see Figure 1). Carpark structures are also naturally suited to the integration of signage, digital media screens, green walls and/or solar panels, which could be other contributors to ignition or fire spread. When designing for such buildings, a holistic approach is needed.

Figure 1: Malmö’s six‑storey Sege Park carpark, which has a mass timber structure. © binderholz. Available at: https://www.binderholz.com/en-us/mass-timber-solutions/sege-park-multi-storey-car-park-malmo-sweden/.

Modern-day vehicles

The predominant fire load in a carpark is the vehicle. Today’s fleet spans petrol and diesel internal‑combustion engine vehicles (ICEVs), plug‑in hybrid electric vehicles (PHEVs), (battery) electric vehicles ((B)EVs), liquefied petroleum gas (LPG) vehicles. Also emerging on the horizon are hydrogen fuel‑cell electric vehicles (HFCEVs).

Each fuel type has its own bespoke set of hazards, although there is some common ground between the hazard profile of the different vehicle types.

Substantial research effort has been invested into understanding the fire characteristics of modern vehicles. ICEVs produce fires which grow steadily, usually with a ‘medium’ growth rate. These fires can be fed by liquid fuels from plastic fuel tanks. High plastic content throughout vehicles increases smoke yields. If the fuel tank is ruptured by fire, a secondary liquid pool fire may occur, which could promote fire spread between vehicles, particularly if the carpark floor slab is sloped.

EV fires have similar growth rates and peak fire sizes to ICEVs but do have some unique hazards. In lieu of liquid pool fires, lithium‑ion batteries can sometimes vent horizontal jet flames, which could also promote fire spread between vehicles – albeit in a different manner to ICEVs. Batteries can enter thermal runaway, which releases toxic gases. Rarely, battery fires can re‑ignite after apparent extinguishment. These characteristics require different firefighting tactics.

Modern-day vehicles – regardless of propulsion mechanism – also have a greater plastic content both in terms of the body of the vehicle itself as well as the internal materials.

As EVs have become more popular, the number of EV-related fires has also increased.[iv] At this stage, however, EV fires remain much less common than ICEV fires. Nevertheless, it may potentially be possible that this may change in the future. Such a change may potentially occur as EVs increase in number, age and become more easily available to a broader range of society. Accordingly, statistics in this regard should be continually monitored. Recent work has already indicated that this may be the case.[v]

Myths, misconceptions and mistakes

Below are some common misconceptions and mistakes when it comes to car parks and fire safety.

1. ‘A carpark fire will be limited to one or a handful of vehicles.’

The commonly cited assumption in fire safety literature from the 20^th century is that fire spread between vehicles is a rare event. This has been challenged by recent major incidents such as those at Liverpool, Stavanger and Luton, which have shown how quickly fires can spread across multiple vehicles and carpark storeys.

These carparks were all densely occupied. For example, in 2023, Luton Airport’s Terminal Car Park 2 fire involved more than a thousand vehicles and led to partial structural collapse.[vi] Aircraft were grounded until the following day, and the carpark was later demolished.

2. ‘Open‑deck carparks can’t burn down.’

In 2020, a multi‑storey, open-deck carpark at Stavanger Airport suffered partial structural collapse from a fire involving approximately 200 vehicles.[vii] This demonstrates that geometry, ventilation and fuel load matter.

A key lesson from this is that open‑deck categorisation should no longer be seen as a silver bullet to justify the use of a structure with very low fire resistance level.[viii]

3.‘All sprinklers go off at once, flooding everything, without the ability of controlling an EV fire.’

In reality, sprinklers operate individually; only the heads heated by the fire activate, and they are highly reliable. There is anecdotal evidence that a ‘typical’ sprinkler system for carparks (ordinary hazard) will control an EV fire in an enclosed carpark.[ix] The fire safety community is currently researching this further.

4. ‘Just add smoke detectors.’

Smoke detection is sometimes proposed as a means to justify Performance Solutions such as extended travel distances, or distance between exits, which are common in carparks.

However, smoke detectors can often be susceptible to false alarms due to exhaust fumes or dust.

5. ‘Smoke can’t reach apartments above a basement carpark.’

Vertical shafts, services risers and compromised compartmentation can allow smoke to spread. Proper detailing, construction and maintenance is the key.

What does the code ask for?

Under the current version of the National Construction Code (NCC 2022), sprinklers are required throughout where a building exceeds 25 m in effective height and for Class 2 or 3 buildings of four or more storeys. Concessions exist for open‑deck carparks and for certain sprinklered carparks, including reduced fire resistance levels (FRLs) and allowance for bare steel in open‑deck structures.

The current ‘status quo’ in Australia for smoke control in carparks is that ventilation systems are operable in a fire event but are not designed as smoke control systems. Upon fire detection, fans exhaust at their peak rate, and supply air systems shut down upon detection of smoke in the supply air. Carpark ventilation fans are not required to be served by fire-resistant cabling. This differs from elsewhere in the world, such as in the UK, where basements are required to be provided with an exhaust system which achieves a set amount of air changes per hour, with components rated to high temperatures.

In 2023/24, the Australian Building Codes Board (ABCB) conducted a review of carpark fire safety provisions to inform future NCC 2025 provisions. The literature review, carried out by Arup, concluded that many code provisions are premised on experiments involving older vehicles (from the late 20^th century) which didn’t exhibit significant vehicle‑to‑vehicle fire spread.

In response, the NCC 2025 Public Comment Draft proposed three key changes as minimum prescriptive provisions:

• require sprinklers in all carparks with more than 40 spaces (including open‑deck),
• require sprinklers to car stackers, and
• remove FRL concessions for open‑deck carparks and for sprinklered carparks beneath other uses in Type A construction.

These recommended changes reflect the hazards present in modern carparks, while retaining a performance pathway for alternative designs with equivalent safety.

It is important that Australia maintains its strong position of having a building code which is swift to respond to a changing world.

Looking forward; suggestions for achieving sustainable, fire safe carparks

The keys to successful, sustainable carpark designs which are fit for the future are engaging stakeholders early, deploying holistic fire safety engineering thinking and keeping the fire strategy simple, durable, and commensurate to the risk. There are now abundant resources for carpark designers to reference. These include publications from the Safety of Alternative and Renewable Energy Technologies (SARET) research program by Fire and Rescue New South Wales.

With sustainable modern vehicles, ‘eliminating’ the risk isn’t feasible. For this reason, attention must shift to ‘reducing, isolating and controlling’.

Good design should be paired with practical management and good safety standards. For this, think positioning of bays, no ad‑hoc storage, robust charging devices, regular monitoring and maintenance and a plan for facilitating prolonged suppression, cooling and/or monitoring of EVs.

[i] Department of Infrastructure, Transport, Regional Develop0ment, Communications, Sport and the Arts (2023, last updated 2025). Towards net zero for transport and infrastructure. Available at: https://www.infrastructure.gov.au/infrastructure-transport-vehicles/towards-net-zero-transport-and-infrastructure. [Accessed 30 September 2025].

[ii] Arup (2024). Fire safety in carparks – ABCB literature review. Available at: https://www.abcb.gov.au/sites/default/files/resources/2024/296877-ABCB-ARUP-Fire-safety-in-carparks.pdf.

[iii] EV FireSafe (2023). All EV types, global, 1st January to 30th June 2023. Available at: https://www.evfiresafe.com/ev-battery-fire-data. [Accessed 30 September 2025].

[iv] EV FireSafe (2024). Passenger EV LiB fires, global, from 2010 to 30th June 2024. Available at: https://www.evfiresafe.com/ev-battery-fire-data. [Accessed 30 September 2025].

[v] Breunese, A., and Both, K. (2025). Probability of fire in electric vehicles: a new perspective. SFPE Europe – Issue 38(3). Available at: https://www.sfpe.org/publications/periodicals/sfpeeuropedigital/sfpeeurope38/europeissue38feature3. [Accessed 30 September 2025].

[vi] Bedfordshire Fire and Rescue Service (2024). London Luton Airport: Car Park 2 Incident Review. Available at: https://www.bedsfire.gov.uk/news/bfrs-publishes-london-luton-airport-car-park-fire-report. [Accessed 30 September 2025].

[vii] RISE Fire Research (2020). Evaluation of fire in Stavanger Airport car park, 7 January 2020.

[viii] Ingolfsson, S. et al. (2024). Revisiting structural fire resistance requirements for carparks, SiF 2024 – The 13^th International Conference on Structures in Fire. University of Coimbra, Portugal, 19 to 21 June 2024.

[ix] European Fire Sprinkler Network (2022). Position paper on sprinkler systems in car parks containing electric vehicles.

By Peter Johnson and Adam Glew,

Adam Glew, Senior Engineer
Arup, Barrack Place, Level 5, 151 Clarence St, Sydney NSW 2000, Australia

Peter Johnson, Arup Fellow
Arup, Sky Park, 1 Melbourne Quarter, 699 Collins St, Docklands VIC 3008, Australia

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