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Report conclusion: More sprinklers needed in car parks

Published: 12.10.22

Vehicles represent a significantly higher fire load than previously assumed. And they are closer than before in underground and multi-storey car parks. This is why DBI recommends sprinklers in more underground and multi-storey car parks than is the case today. With retroactive effect.

Vehicles are not what they used to be. Firstly, they are not only powered by combustion engines, but are also available as electric and hybrid vehicles. Secondly, they increasingly contain plastic materials and electronics. Both affect the fire safety properties of a vehicles, which can have consequences for fire safety in underground and multi-storey car parks, also known as indoor parking facilities.

The Danish Housing and Planning Authority therefore asked DBI (The Danish Institute of Fire and Security Technology) and the Danish Technological Institute to investigate fire safety in indoor parking facilities in Denmark, and this assignment has now become a report entitled ‘Fire safety in indoor parking facilities, storage of lithium-ion batteries and batteries for solar panels in buildings’.

- The report takes a closer look at the consequences that the general trend in the automotive sector has on safety and the possibility of measures being taken in indoor parking facilities, says Lars Vædeled Roed, Fire Safety Adviser at DBI, who was involved in producing the report.

More energy and less space

The report also includes a study of literature that reveals many interesting aspects. For example, the fire load of a new vehicle – whether it is an electric vehicle or a conventional vehicle with a combustion engine – is approx. 40% higher than the fire load that was previously expected.

- There’s actually no major difference between electric vehicles and conventional vehicles in relation to fire load. The literature study shows that the high fire load comes from the vehicles’ materials, which consist of more and more plastic. Vehicles are also getting bigger and bigger, says Lars Vædeled Roed.

Furthermore, the space between the vehicles in indoor parking facilities has become smaller, because space is prioritised for more vehicles. The parking bays and the entry and exit roads are narrower, which increases the risk of fire spreading between vehicles. The study also shows that electric vehicles seem to catch fire less; on the other hand, they present a tactical intervention challenge when they do catch fire. Partly due to difficult access to the battery, and partly due to risk of thermal runaway (where the battery generates heat on its own over a long period of time and can catch fire) and a consequent need to remove the electric vehicle from the indoor parking facility.

Recommends sprinklers in new and old facilities

Based on the literature study, the report also includes a risk assessment and analysis of personal safety in indoor parking facilities, and a review of the Danish rules and guidelines for the construction of indoor parking facilities. And the conclusion from DBI in this respect is clear.

- With a greater fire load from vehicles and narrower parking bays, the risk of fire spreading is greater than before, and the conditions for a successful response from the emergency services are poorer. This means that indoor parking facilities that are protected through fire safety dimensioning in accordance with the previous criteria, for example, can be problematic, because they were designed on the basis of a lower fire load and a limited number of burning vehicles. In such cases, it will be necessary to revisit the dimensioning, says Lars Vædeled Roed.

But indoor parking facilities that have been approved in accordance with the Example Collection and in the pre-accepted solutions for building regulations in the area may also be problematic.

- The existing requirement for sprinklers in indoor parking facilities applies for most facilities measuring 1,000 m2 or more. But the risk of fire spreading is also too high in smaller facilities, so the report’s recommendation is that all indoor parking facilities over 150 m2 should be fitted with sprinklers. This applies in particular to buildings that also contain building sections where people stay overnight, e.g. multi-storey housing, hotels, care homes, etc., says Lars Vædeled Roed, continuing:

- The recommendation covers both existing and future facilities – and also facilities of less than 150 m2 where there are more than 6–7 vehicles. Temperature curves have been observed abroad in connection with fires in indoor parking facilities that were more severe than the standard fire curve, he says.

The risk of fire in indoor parking facilities is particularly high when the facility is part of another building – in the form of an underground car park, or when the lowest floors of a building are used for parking.

Natural fire ventilation or not

The report also questions the option of using natural fire ventilation. The concept is that a given percentage of open façade can conduct heat away from a possible fire and thus prevent the spread of the fire. But many examples have been seen abroad of rapid fire spreading in open indoor parking facilities with fire ventilation via the facade.

- We’re not sure whether this concept works in reality. If the sprinkler requirements are not dimensioned correctly, it’s also not certain that the requirements for ventilation, and thereby the possibility of using natural fire ventilation, are too, says Lars Vædeled Roed.

It is also recommended that there should be an automatic fire alarm system, as studies of fires show that it is not possible to count on users who have parked their vehicles alerting the fire brigade in the event of a fire.

Reason to take a look at the regulations in this area

Does this mean that all indoor parking facilities are ticking time bombs, you might ask yourself? Not quite.

- To see an incident with major consequences, other factors must coincide – such as fire and maximum personal load. The report describes the area and indicates that there is good reason to take a look at regulations and guidelines retrospectively. Even though people in a indoor parking facility can get out in the event of a fire, the fire can affect the rest of the building, the loss of value will be significant and the building will subsequently be unusable for a longer period, says Lars Vædeled Roed.

DBI and the Danish Technological Institute have submitted the report to the Danish Housing and Planning Authority, which is the government agency in this area.

The report can be read in full in Danish on the Danish Housing and Planning Authority’s website:

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Lars Vædeled Roed

Fire Safety Adviser

+45 20 21 89 01