Are we solving the wrong problem in car park fire safety?

Proposed updates to Approved Document B (AD B) would increase the required fire resistance of open-sided car park structures to 30 minutes and up to one hour. It is an acknowledgement, at last, that the fire exposure has changed. But while a stronger structure may stand for longer, it does nothing to stop a fire spreading in the first place, and that is the question the industry needs to question and answer writes Tom Roche, Secretary at the Business Sprinkler Alliance.

Cars are bigger than they were a generation ago. Heavier with plastics and combustible materials, the modern car burns hotter and faster as a result. This is not about electric vehicles it is just that the old assumption that a car park fire would be limited to one to three vehicles is no longer sound. Modern fire loads mean that once a fire takes hold, it is more likely the fire will spread to neighbouring vehicles and with more adjacent vehicles that fire can keep spreading. Therefore, the window for intervention is narrowing.

This is where the increase in fire resistance proposal falls short. A more resilient structure is a worthwhile objective as it protects against collapse and gives emergency services more time to operate. However, if the fire can spread and the scale of that fire mean that the fire service cannot stop it, what will the extra time gain you? It does not address the fundamental challenge: how do we stop the fire spreading in the first place?

Recent research commissioned by the Health and Safety Executive, Real Fires: Open-sided Car Parks, confirms what fire services have been saying for some time. Car park fires today develop faster, involve more vehicles and place greater demands on structures than the scenarios our regulations were written for. The consequences, as seen at Luton Airport in 2023 and the Kings Dock car park in Liverpool at the end of 2017 are global examples of the impact of these spreading fires.

Perhaps an element that is missing in the discussion is that not all open sided car parks are equal. A slightly odd thing to say, but some car parks form part of critical infrastructure or local community assets. If they are lost or damaged such that their use is restricted, they in turn have an impact on other services.

Consider the Luton Airport car park fire. People talk about the scale of the event. The damage in terms of the number of cars lost and the costs involved to rebuild the car park rebuild. However, the discussion in terms of impact on the airport from lost revenue from the car park, trade and disruption to passengers are missing. Some may see this as outside the scope of regulatory guidance, others may read it as an indication that these impacts are limited. Many will therefore be stunned to find the figures in the annual accounts of the airport detail insurance recoveries for business interruption and additional cost of working totalling £49 million. This is not for the car park rebuild or the cars damaged – this is impact on the business. That is not the end of it as these figures do not include the entire timeframe to the reopening of the rebuilt car park.

To make the point a bit further. The fire at Addenbrooke Hospital car park in Cambridge on 13th December 2025 illustrates this potential infrastructure impact. Caused by a mechanical fault in a diesel vehicle, the blaze spread to 12 vehicles and forced the partial closure of Car Park 1, leaving 77 spaces out of use at one of the UK's major hospital sites well into 2026. The fire itself was limited but required firefighters from several counties to attend to support the local fire service to suppress the event. It is a telling example of how even a relatively modest vehicle fire, in the absence of early suppression, can have larger impacts and lasting consequences.

The case for early intervention is clear. Blocking fire from spreading using barriers may be an effective strategy to limit the fires to a manageable number of cars, though car park users may dislike the solution. A fire suppressed in its early stages, before it spreads beyond the vehicle of origin, avoids all of those consequences. Automatic fire suppression systems such as sprinklers have proven do precisely that. Evidence from protected car parks in the UK shows fires being contained at an early stage, in stark contrast to unprotected facilities where fires have escalated rapidly and caused structural damage.

Increasing structural fire resistance is not the wrong answer. But it is an answer to a different question. It leaves the question of what to do with the fire spread to be considered by the designers. If we are serious about tackling the growing risk in car parks, we need measures that address fire spread directly and consider the relative importance of these car parks to our infrastructure and local services. Sprinklers should be a fundamental part of that conversation, and of any updated regulatory guidance.