As a follow-up to the July 24, 2023 article, this article examines the next steps in the fire risk assessment process in buildings (ref. Figure 1 [1])
Hazard, event and scenario identification
A hazard is a condition or physical situation with the potential to cause harm or damage to the object of the risk assessment (e.g. people, property, business continuity). The threat posed by the hazard is the basis for identifying scenarios. If the potential for undesirable consequences of the hazard actually occur, it constitutes an event. A fire scenario is a fire incident characterized by a series of events. Fire hazards include heat sources (potential for ignition) and combustible materials (type, location, products of combustion). Heating equipment can be a fire hazard. An additional hazard could be an earthquake, which could bring heating equipment into contact with unwanted flammable material. If the material catches fire because the heating equipment was knocked over in an earthquake, that’s an event. If the fire spreads to neighbouring objects and continues to grow, this is a scenario..
A fire scenario is a qualitative, time-sequence-based description of a fire that identifies key events characterizing the fire. The fire scenario should describe the fire from initiation to burning or extinction, including the operation of the passive or active fire protection systems involved. It must also identify who or what is exposed to the fire and the extent or severity of the damage.
Clusters are another term used in fire risk assessment and are groups of scenarios that have some but not necessarily all common characteristics and are expressed at a level of detail suitable for engineering analysis. Scenario clustering is necessary because each individual scenario (sequence of events) will have negligible frequency data. For example, a fire scenario might begin like this: “A lit candle tips over on an upholstered chair in а living room. The chair catches fire and the fire grows.” Frequency data for this exact scenario may not exist. However, the scenario group could be: “An open flame ignites a flammable combustible material in a residential area.” Data to support an estimate of the frequency of this scenario cluster can be found in various resources such as statistical reports by NFPA and other similar organizations.
Frequency analysis, consequence analysis and data analysis
A key factor that differentiates a fire risk assessment from a fire hazard analysis (FHA) is the inclusion of an estimate of the likelihood of an event or scenario occurring. Frequency analysis requires data from reliable sources. This may include entities such as NFPA, and other similar organizations that report fire statistics; insurance companies that collect fire data; as well as manufacturers or other organizations by monitoring the safety of production processes and having data on the reliability of components and production systems.
Databases such as NFIRS (National Fire Incident Reporting System, USA) capture data on the extent of fire spread (e.g. by type/item of origin, location of origin, etc.) which can be useful in examining the reliability of containment.
Consequence analyses are often performed by experts using analytical or computational methods, evaluating factors such as the effectiveness of the building’s fire protection systems for the specified fire scenario. However, they may also use historical data from similar cases, at least as a basis of comparison. Expert judgment can also be used for screening purposes.
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References:
[1] http://fire-techinfo.com – ОFire risk assessment in buildings – a general overview
[2] http://sfpe.org – Аn оverview of аpproaches and resources for building fire risk assessment
[3] SFPE Engineering Guide – Fire Risk Assessment, Society of Fire Protection Engineers
