The LWF Blog

Passive Fire Protection for Building Professionals – Part 19

May 28, 2020 9:58 am

In LWFs blog series on passive fire protection for building professionals and contractors and those with an interest in structural fire protection issues, we aim to give an overview of the important role passive protection plays in the overall fire safety provision of a building. In part 18, LWF looked at the construction of fire-rated ceilings to avoid the spread of fire in a building. In part 19, LWF will discuss ducting, an important area in the provision of passive fire protection to a building.

In order to preserve passive fire protection in a building, it is important that ducting systems are protected to prevent the spread of smoke and fire between compartments in the building. Fire protection for ducting takes the form of fire-rated ducting and dampers. All buildings require sufficient air flow which may take the form of air conditioning systems, warm air heating or ventilation systems, such as the types used in car parks and in staircase ventilation.

Air extraction systems used in kitchens and other plant rooms may also provide a fire hazard as they are designed to remove air from high-risk areas. When considering the movement of air around a building by whatever means, it is important to also see this as a conduit for smoke. Both air and smoke are effectively gases and their movement will be the same.

While air moving around a building is not a safety issue in itself, the movement of smoke in sufficient concentration is highly flammable and easily can cause fire spread and development.

Every point at which the fire-rated construction is penetrated by air handling ducting must be considered, as each point is a potential source of compromise for the fire resistance of the building. The most appropriate method of protecting the building from this fire risk must be decided upon from the choices available.

The first possible form of protection is the use of a damper. Some dampers are activated via a thermal device – a heat detector or fusible link. The type of thermally-activated fire ducting damper most commonly used, however, is a metallic device which, when heated, releases a sprung shutter.

Such dampers are ideal for preventing the spread of fire through ducting, but are less effective at preventing the spread of smoke. It is important that the damper device chosen is appropriate for the environment in which it is to be used. If the damper is to prevent fire spreading from a compartment into a means of escape, it should always be a fire and smoke rated damper.

In part 20 of this series, LWF will continue looking at fire dampers for ducting and how to choose the correct type of damper for the environment. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.

Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.


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