Last edited 27 Feb 2019

Fire separation

Fire separation.jpg

[edit] Introduction

Fire separation is the method for protecting buildings from the spread of fire into adjoining areas for designated time periods by the introduction of fire resisting walls, floors, doors, ducts and so on. These time periods are set out in the Building Regulations. These constructions divide the building into distinct fire zones called ‘fire compartments’. In such cases, the walls and floors are referred to as compartment walls and compartment floors.

In general, when any of those elements is prefixed by the word compartment, it designates that it has been designed and constructed to have a specific period of fire resistance, typically for 30, 60, 90 or 120 minutes. The level of performance will depend on the type of building in question and the requirements of Approved Document B of the Building regulations (England and Wales) or Part E (Scotland and Northern Ireland).

The period of time during which the element acts as a barrier to the spread of fire is intended to prevent it from developing into a much larger fire, to give people in adjoining accommodation sufficient time to escape, and to limit the damage caused.

In cases where a fire separating element includes an opening, such as a door, internal window, penetrating duct or access panel, it must have the same fire rating as the element in question in order to maintain the fire separation qualities of the construction.

When a duct penetrates a compartment wall or floor, it must be ‘fire stopped’ (ie material is packed around the duct to create a seal and so achieve the same fire resistance as the wall or floor and ensure the opening does not form a route for fire spread). Fore more information see: Fire stopping.

Fire dampers are installed in the ducts of heating, ventilation and air conditioning systems which penetrate fire-resistant constructions and will automatically close on the detection of heat.

In a simple four-storey office building, with each floor comprising two escape stairs and an open plan office area with no internal partitions, the escape stairs will be enclosed by fire walls and fire doors. This makes each staircase a multi-storey fire compartment which will be designed to ensure that any outbreak of fire in the office areas cannot penetrate into the protected stair for the designated fire period.

An office building of greater complexity, eg with separate meeting rooms, canteen areas etc, may have a more complex fire compartmentation requirement and more fire compartments. Other considerations that will affect the degree of sub-division are the height of the building, its fire load and the availability of a sprinkler system.

For more information see: Fire compartmentation.

Fire separation and the creation of compartments has generally proved to be a successful system of containing fires in buildings and so reducing loss of life. However, problems may arise during periods of maintenance or refurbishment when old elements are replaced, and/or new constructions introduced that compromise or do not meet the original fire safety levels.

[edit] Related articles on Designing Buildings Wiki