The LWF Blog

High ceiling clearance space | Pt 1 – The challenges of effective fire protection through sprinklers

October 29, 2013 11:36 am

Modern architecture for buildings such as shopping malls, public concourses, atrium spaces etc. has led to increasingly high ceiling clearance spaces. A standard installation of sprinklers in ceilings such as these can cause issues. The sheer amount of space between the source of the sprinkler system and the base of the fire (most commonly on the ground) means that ineffectiveness of fire suppression becomes a real issue.

The decision on sprinklers is an important one. There are not too many alternative fire protection schemes available for buildings with high level ceiling clearances. As a result, the part of the facilities with high clearance spaces could be left without an effective means of automatic fire suppression protection.

There has been extensive research into issues such as this, and in many cases, specific solutions to the problems developed; e.g. control the fire load as recommended in BS 9999 Code of practice for fire safety in the design, management and use of buildings. However, the issue remains for many new projects.

This problem introduces a unique challenge to fire safety engineers and approval authorities, when sprinkler protection is recommended in the Building Regulations – Approved Document B: 2006, that where sprinklers are provided, it is normal practice to provide sprinkler protection throughout a building.

Potential problems with sprinkler protection

With the normal layout of sprinkler design and conventional ceiling heights, the sprinkler heads will provide sufficient water to suppress or extinguish the fire in its early stages. 

Where the ceiling level is high, the sprinkler heads are more remote from the fire source and this distance raises serious doubts as to the successful fulfilment of the functional objectives of sprinkler system, i.e. detection, location and control of the fire. 

Results from the fire/smoke modelling, i.e. Computational Fluid Dynamics (CFD) indicate that in a large concourse area, a sprinkler head 20m directly above an unshielded fire would require approximately 6 minutes to be activated. The fire grows to an unconstrained size by the time the sprinkler becomes operational. It therefore follows that the greater the distance of the sprinkler head is from the fire source, the larger the fire size becomes before the sprinklers are activated. This therefore reduces how effective the system may be in suppressing the fire. CFD analysis has shown that compartments of great height and width can allow the chance of failure for the suppression system to perform its functional objectives.

This fundamental problem has led to the limitation of the use of sprinklers within facilities that have areas with high ceilings and the unfulfilled use of such areas. In many cases there cannot be anything other than basic activities, such as reception areas. The restriction in terms of controlling the fire load has been outlined in BS 9999 and will be discussed in more depth in the next article in this short series.

The second and final part ‘High ceiling clearance space | Pt 2 – Published guidance and potential solutions for sprinkler issues’ will be published next week.

In the meantime, if you would like more information on fire suppression solutions and fire engineering designs, simply call Peter Gyere at Lawrence Webster Forrest on 020 8668 8663.

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