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A Fire Behavior Analysis to Evaluate Clearance Requirements Around Structures in Ventura County, California as it Relates to Firefighter Safety

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Ventura County Fire Department (VNC) in California hired AMSET to conduct a fire behavior analysis that would validate Ventura County’s 100-foot clearance requirement around structures as it relates to firefighter safety. In addition, VNC requested that we evaluate site specific locations where 100-foot clearance may be inadequate for safe operational space for firefighters.

We determined that safe operational space for firefighters should utilize the same guidelines that are used for a wildland fire safety zone. A safety zone is defined as a preplanned area of sufficient size and suitable location that is expected to prevent injury to fire personnel from known hazards without using fire shelters.

Sufficient size for a safety zone is a minimum of 4 times the height of a flame length. This guideline is considered a minimum for radiant heat only. Convective heat from wind and/or terrain influences will increase this distance requirement. The guideline assumes that there is no wind or slope. Areas with these influences would need greater distances than those recommended in this analysis to provide for firefighter safety.

The analysis demonstrated that additional clearance would be needed for firefighters to safely engage in structure protection actions within many of the sites. The physical location of structures in relation to topography, fuels, and wind creates varying needs for clearance; in some cases minimum clearances of up to 300 feet would be needed based on safety zone guidelines.

Validation of 100 Foot Clearance Requirement