Updated 07 October 2020
Risk is measured by calculating the extremes of a hazard verses the likeliness of the hazard turning into an issue. Take two tower blocks as an example:
A ten story building verses a three story building
The taller premises might take longer to evacuate so with all hazards being equal, the taller premises has a higher risk, but if the tall premises has superior fire prevention measures in place it could be deemed a lower risk than the three story premises without those same measures.
Assessors look at the adequacy of current measures and for any shortcomings. Measures can’t be assessed in isolation so assessors look at the effect of a combination of measures. An example is this escaping from a fire scenario where there are a number of variables unique to every premises:
Escaping from fire
Assessors will often use a matrix: Likelihood of fire versus the likely consequence of fire to identify a risk rating. Five ratings, such as in this example: Trivial, Tolerable, Moderate, Substantial and Intolerable; provide a wide scale.
| Trivial Harm | Slight Harm | Moderate Harm | Extreme Harm | |
| Low | TRIVIAL | TOLERABLE | TOLERABLE | MODERATE |
| Medium | TOLERABLE | TOLERABLE | MODERATE | SUBSTABNTIAL |
| High | TOLERABLE | MODERATE | SUBSTABNTIAL | INTOLERABLE |
When assessors find risks outside of the tolerable range, they will recommend measures to lower the risk. Recommended measures must be practical, proportionate and prioritised, they should comply with legislation and the organisation’s fire safety policy.
The risk assessor should be confident that once their recommendations have been implemented, the risks are considered at least tolerable.
There is always room for improvement and low cost improvements to fire safety are always good investments. That being said significant expenditure must be wholly justified with a realistic scenario, in which unacceptable fire risk to occupants would occur.