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Assessment of Fire Risk in U.S. Residences

Robert Hanson

State Farm

Recent research from UL and NIST has suggested that the level of fire hazard in the contemporary homes is greater than the older homes. The major factors contributing to the increase in the fire hazard are light frame floor construction, open plan construction, and contemporary furnishings reaching higher peak heat release rates in shorter times than older furnishings.

An analysis of fire incident data from the National Fire Incident Reporting System (NFIRS) was conducted to assess the role of smoke detectors and sprinklers in mitigating property damage caused by fires. Data was examined to determine flame spread characteristics for those residences with or without residential sprinklers and smoke detectors. Trends in fire characteristics and fire protection systems are reported. Figure 1 illustrates the performance of sprinklers in one- and two-family residential buildings.


Figure 1 - Sprinkler Performance
Fig. 1: Sprinkler Performance


Fire modeling was conducted to assess the impact of differences in furnishing characteristics and open plan designs on fire severity as well as the time reach peak severities. Severities are described in terms of smoke temperatures and extent of fire spread. The building characteristics were based on the residential characteristics for the different time periods. Fire scenarios were deducted from trends found from the analysis of the NFIRS data and a literature review.

The NFIRS data was also examined for the most prevalent items first ignited in fire incidents depending on where the fire started. Estimated property loss values were used to give a risk weighting for each of the fire spread categories for the different area of origins. There are five possible fire spread categories: confined to object of origin, room of origin, floor of origin, building origin, and beyond building of origin. The contribution of the top items ignited to the total risk value is illustrated in Figure 2.


Figure 2 - First Ignited
Fig. 2: First Ignited