The LWF Blog

Fires in Car Parks – Regulations and Fire Prevention – Part Two

July 2, 2014 4:48 pm

The first part of this two-part blog looked at the potential causes of fire risk through ignition in car parks. This second part will lay out the Building Regulations relating to fire in car parks and will look at fire prevention measures which can be employed by Architects and Building planners, in conjunction with Fire Engineers, to reduce the likelihood of fires and control the effects of fire in car parks.

The Building Regulation requirements

The main intention of Approved Document B (Fire safety) – Volume 2 – Buildings other than dwellinghouses (2006 edition incorporating 2010 and 2013 amendments) in relation to car parks, is to protect those occupants needing to evacuate by avoiding the build-up of smoke and toxic gases; to prevent the spread of fire from one storey to another, and to assist the fire service in their operation.

Current legislation states that car park premises must be provided with a means of ventilating the area, and be separated from other parts of the premises with fire resisting construction. ADB recommends three different methods: 

• open-sided (high level of natural ventilation)

• natural ventilation (other than open-sided)

• mechanical ventilation

Open-sided ventilation relies on the structure of the car park together with its capacity to naturally ventilate smoke and hot gases. Each storey should be naturally ventilated by permanent openings at each car park level, with an aggregate vent area of not less than 1/20th of the floor area at that level, of which at least half (1/40th) should be equally provided between two opposing walls. 

Natural ventilation other than open-sided can be used to extract smoke and hot gases where more limited natural openings exist. Each storey should be ventilated by permanent openings at each car parking level, having an aggregate vent area of not less than 1/40th of the floor area at that level, of which at least half (1/80th) should be equally provided between two opposing walls. 

If smoke extraction via natural ventilation is not possible due to the design of the car park, a mechanical ventilation system must be installed. This should be independent of any other ventilation system and be designed to operate at 10 air changes per hour, in the event of a fire. All components should comply with BS EN 12101-3:2002 Smoke and heat control systems. Specification for powered smoke and heat exhaust ventilators. 

Compartmentation in Car Parks

Compartmentation will prevent the spread of fire and smoke throughout the building and adjacent areas. For this reason, both internal and external fire spread possibilities are considered. 

Where a building contains a car park, separation between the car park and the rest of the building must ensure a certain level of fire resistance. The level of resistance depends on the type of smoke-ventilation system used in the car park. The ADB allows for a reduction in fire resistance when open-sided ventilation is used, compared to mechanical ventilation and natural ventilation other than open-sided, where the level of fire resistance is higher.

Fire precaution systems in car parks

The types of fire precaution systems likely to be installed in car parks will vary between premises. 

One or more means of ventilating smoke and heat are required in all car park premises. The level of ventilation deemed to be sufficient by ADB has been proven by research to vastly reduce the likelihood of fire spread between adjacent cars, irrespective of fire brigade intervention. As an additional measure of protection, however, automatic fire detection is usually provided in the area to enable a rapid response to a fire incident.

The ‘impulse fan’ is a recent innovation. These systems, installed at strategic points, will drive smoke and toxic gases towards the extraction points. Tests carried out by various manufacturers have demonstrated the effectiveness of this system. Impulse fans are not stated in any prescriptive codes, and up until now have been used as a part of a fire engineered solution.

The best solution currently available to designers and architects is not necessarily set down in prescriptive legislation and guidance; it all depends on the specific characteristics of the car park. As all buildings are different, it is essential that fire protection solutions are designed on an individual basis.

If you have any queries about fire risk assessment, fire engineering, fires in car parks or your own building project, please contact Peter Gyere on 0208 668 8663 for more information or to speak to one of our Fire Engineers.

Lawrence Webster Forrest is a fire engineering and fire risk management consultancy established in 1986, with experience in the development of fire engineered technology and the application of fire safety standards including fire engineered techniques.