In a fire risk assessment, it is reasonable to make certain assumptions regarding compartmentation, based on the judgement of the fire risk assessor. This does not mean that matters such as compartmentation, fire stopping, etc are entirely outside the scope of the fire risk assessment required by fire safety legislation. Reasonable endeavours should be made to, at least, sample fire stopping in areas where there is obvious potential for inadequate fire stopping of, for example, service penetrations. (eg. in readily accessible service risers), and to consider, by sampling whether cavity barriers are located at readily accessible critical locations, in which there might be reasons to assume the occurrence of deficiencies.

It will often be very difficult to ascertain whether fire and smoke dampers have been provided at all appropriate locations. Again, it may be reasonable to make certain assumptions in this respect.

If a building has been constructed, or converted under modern building regulations, it will often be reasonable to assume that compartmentation is adequate; a completion certificate issued under the Building Regulations is evidence (though not conclusive evidence) of compliance with the requirements of the Regulations in respect of compartmentation (and other functional requirements of the Regulations).

In a type 1 fire risk assessment for a block of flats, it is not expected that there should be access to flats to check compartmentation, though if there are grounds to suspect that there may be significant deficiencies, the fire risk assessor might recommend a more intrusive inspection; however, this will be the exception, rather than the rule.