Compartmentation or compartmentalisation are concepts that are crucial to building fire safety in the United Kingdom, but which are routinely undermined and misunderstood by those engaged in installing systems and maintaining buildings.

What is compartmentation?

Simply put, compartmentation is the process of dividing a building into compartments that are independent of one other.

Why is compartmentation important?

Compartmentation in buildings is an important concept in fire safety. If the building is constructed, maintained and used correctly, a fire should be contained within the compartment of origin for the period it was intended to be. This should ensure that the means of escape remain viable for a period of time, or provide the assurance needed behind any ‘stay put’ or phased evacuation strategies. More on those another time.

When fire, heat, smoke and the products of combustion are able to escape the compartment of origin sooner than intended, the viability of the means of escape and other compartments in the building may be threatened sooner - with implications for the successful evacuation of the building.

How is compartmentation defeated?

To be usable within buildings, compartments need to be penetrated in a number of ways - these penetrations present weaknesses within the building that, if not properly controlled, may allow fire to spread to adjacent compartments.

Fire doors

It is necessary to move between compartments through door apertures. To prevent smoke, heat and fire spreading between compartments fire resisting doorsets are used, the doorsets will be fire rated to a period of resistance. To ensure that the doorset performs to that rating it is important that the doorsets are fitted correctly, and inspected regularly to identify deterioration in condition.

It does not matter how good a fire door is though - it will not act as a fire door if it is wedged open, and doing so will damage the door fit and door furniture. Where there are genuine operational reasons to hold doors open, then using hold open devices interfaced to the detection and warning system, and checking their function regularly, is much more effective.

Service Penetrations

Even in new buildings, services need to pass between compartments. Examples include electrical circuitry, air movement systems, IT cabling, water, gas and waste distribution. It is important that all service penetrations are appropriately fire stopped, using fire rated materials, by a competent fire stopping professional who is able to certify the works. These service penetrations should be asset tagged, inventorised in the building O&M manual, and inspected periodically for deterioration thereafter.

It is important that the same principles are applied to subsequent modifications to the building, so that as the building is updated and maintained over time, its compartmentation strategy does not break down. As service penetrations are often hidden within voids, it is important that works are checked at completion and prior to acceptance to ensure that the building compartmentation strategy has not been compromised.


Fire may also spread between compartments through glazing. Internal glazing onto escape routes should be manufactured of fire rated construction.

External Wall Systems

In extreme cases, where fire has broken out of the compartment of origin through the external windows, it is possible that fire can spread over the external facade to the building, with heat and smoke impacting other compartments.

To summarise, the concept of compartmentation is central to the successful evacuation of buildings in the UK, on the one hand securing the viability of the means of escape, and on the other the assurance behind ‘stay-put’ and phased evacuation strategies in certain buildings.