Process of fire risk assessment:
In the UK, the process for the FRA came out of the process for a general risk assessment.
In a general risk assessment hazards are identified, the people at risk are identified, the risk is evaluated and remedial action is taken to either completely remove the risk or to reduce it to an acceptable level. For example, the risk posed by an electrical lead trailing across a floor where people have to pass can be removed by providing a fixed cable attached to the wall instead of the trailing cable. Alternatively it might be considered acceptable not to remove the risk but merely to reduce it by warning people who use the area to watch out for the cable and step over it.
This process is fine and it has been applied to FRAs. However, that process is not enough for FRAs. A FRA will identify risks such as, perhaps, welding taking place near some combustible items and will take steps to reduce the risk in some appropriate way but then it has to go further. After the FRA has identified and dealt with all the matters in the building that might lead to fire it then has to assume that there is a fire in the building anyway and it has to make sure that the means of escape can be safely used by all occupants of the building even though there is a fire. The fire risk assessor has to consider different locations for the fire, seeking out the worst locations and then he has to consider if everyone could get out of the building safely, without the need for outside assistance, if there was a fire in one of those worst locations. In the FRA process we do make the assumption that there will only be a single fire in the building at any one time.