The determination of the source of fire is one of the most important parts of conducting a fire risk analysis. To determine the source of fire, a design fire scenario must be developed. A fire scenario is a set of conditions that defines the development of fire and the spread of combustion products. Fire scenarios comprise three sets of characteristics: characteristics of the building, characteristics of the occupants, characteristics of the equipment, properties and characteristics of the material, environmental characteristics and characteristics of the fire.
A design fire scenario is a set of conditions that define the critical factors to determine the results of fire protection designs for testing new buildings and facilities or modifications to existing facilities. The design fire scenarios are the fire scenarios that are selected to analyze a test design.
Performing the Fire hazard analysis
Performing a fire risk analysis (FHA) is a fairly simple engineering analysis. The steps include the following:
- Selecting a target outcome.
- Determining the scenario(s) of concern that could result in that outcome.
- Selecting an appropriate method(s) for prediction of growth rate of fire effects.
- Calculating the time needed for occupants to move to a safe place.
- Analyzing the impact of exposure of occupants or property to the effects of the fire.
- Examining the uncertainty in the hazard analysis.
- Documentation of the fire hazard analysis process, including the basis for selection of models and input data.
Design fire scenarios:
Design fire scenarios differ by occupancy and should be based on reasonably expected fires and worst-case fires. if a fire may be technically plausible but is extremely unlikely, that scenario may not be necessary to include in the design fire scenarios.
Determining the Scenario(s) of Concern:
Records of past fires, either for the specific building or for similar buildings or class of occupancy, can be of substantial help in identifying conditions to be avoided. Statistical data from National Fire Protection Agency (NFPA) or from the National Fire Incident Reporting System (NFIRS) on ignition sources, first items ignited, locations of origin, and the like can provide valuable insight into the important factors contributing to fires in the occupancy of interest.
Bounding Conditions:
When conducting a hazard analysis, it is important to consider the types of changes that may occur. If the hazard analysis only considered a specific set of initial conditions, then it would be necessary to revise the fire hazard analysis any time changes were made in the future. Bounding conditions must be clearly identified because changes in the building may occur.
Implied Risk:
The primary risk factors involved are included in the design fire development. The design fires should include such accidents as gasoline tanker trucks crashing into the side of the facility or bombs ignited at the base of the building.
Data Sources:
It is useful to have data on which to base future quantification. Members of the National Fire Protection Agency Life Safety Code Technical Committees developed the design fire scenarios based on statistical analyses prepared by the National Fire Protection Agency Fire Analysis and Research Division and also on past fires that have occurred in different occupancy types. Other sources addressing typical fires in occupancies include Factory Mutual (FM) data, state or local jurisdiction data for various occupancies, the National Fire Incident Reporting System (NFIRS), or past fire history published in the National Fire Protection Agency Journal.