Qualitative risk assessment - fire protection engineering:
NFPA 551 discusses the differences between qualitative risk assessment and quantitative risk assessment.
Qualitative riskassessment is where no numbers are used in the process but judgements are made on relative likelihoods and outcomes. Quantitative risk assessment uses numbers to produce results and comes up with what appear to be hard and fast figures. Of course, they are not usually hard and fast, but they can be generally indicative of the true situation.
The document states that it is important that a FRA states its objectives and scope. The reader of the FRA should know what it is trying to demonstrate including the extent to which it is trying to demonstrate it.
It also states that data sources should be provided along with any assumptions that have been used in the assessment.
All assumptions should be justified by the author of the FRA. Typical assumptions might be, for example, the maximum number of people in a room, the wind direction, the amount of combustible items in an area, the manner in which the building will be maintained, etc. Any assumptions like these that may have an influence on the outcome of the analysis should be stated and justified.