Ignition risk analysis — cigarette ignition of upholstered furniture

Abstract

A general analytical framework for ignition, which addresses the impact of fuels, ignition sources, and other human and mechanical factors, was developed with a “Fault Tree” technique. The developed framework was then used to analyze fire incidents involving cigarette ignition of upholstered furniture in the living room of single residential homes (1 and 2 family dwellings) from 1975 to 1982.

The annual incident rate was calculated using the national estimates of the incident, based on the NFIRS data and the number of housing units. Analysis of previous test data from CPSC's full scale tests and the California Bureau of Home Furnishings' (BHF) mockup tests indicates that cigarette ignition of upholstered chairs is mainly dependent on the combination of materials used as the cover fabric and the stuffing material. Based on these test data, ignitability was estimated for eight types (combinations) of chairs. The average ignitability of chairs produced in a given year was then calculated from these ignitabilities and the distribution of the types of chair produced in that year, estimated from the annual material consumption by the industry. Average ignitabilities of chairs by the year produced, were then used to estimate the average ignitability of chairs in use in a given year. A “Product Life Model” which assumes normal distribution and a mean life of 15 years, with a standard deviation of 7 years, was used to calculate the distribution of chair population in a given year, by the year produced.

Results of analysis showed that the annual incident rate, from 1975 to 1982, is closely correlated with the product of annual cigarette consumption rate and the average ignitability of the chairs in use, as predicted by the framework. This tends to suggest that other factors, such as human behavior pattern of misuse, furniture density (load) in the housing units, etc., did not change significantly during this period, 1975 to 1982.