An examination of escape times in a mock residential test house by analyzing smoke filling and detection times for couch fires in a living room

Abstract

A series of full-scale multi-compartment and multi-storey fire experiments are undertaken to evaluate the potential “available safe escape time” (ASET) in fires fueled by different upholstered furniture types, burning under controlled ventilation conditions in a representative multi-storey residential dwelling. Ten different furniture fire experiments are conducted to fill key gaps in current understanding of fire growth and behavior, smoke filling, detection times, and available escape times in limited ventilation conditions as established within the well-instrumented “burn house” at the University of Waterloo Fire Research Laboratory. Findings for mass loss rate, smoke movement and resultant visibility, oxygen consumption, and the evolution of carbon monoxide along the “escape path” are compared across furniture types. An estimate is made for the available escape time accounting for occupant movement while upright, or when the environmental conditions deteriorate, movement out of the house by crawling. Findings show that the North American furniture fires result in crawl-out available escape times between 96 and 238 seconds whereas the UK furniture fires have significantly longer crawl-out available escape times, between 281 – 1487 seconds.

In slower-burning fires, the importance of considering the incipient fire time in comparing detector response highlights the benefit of placing detectors near fuel loads in living areas, which in this study allows for a 127% increase in available escape time. An overall increase in available escape time of 19 – 50% is found for the fast-burning North American furniture. Flame-retardant interliners, combined with flame-retardant treatments, are observed to significantly limit the exposure and participation of the polyurethane foam in the fire, controlling fire growth in one instance and preventing sustained ignition in two other couches. Further examination of key elements of furniture fire behavior illustrates that ignition, incipient fire time, growth period, and peak mass loss rate are critical functional parameters. These can be used to define a scoring system by which to compare the fire performance of different couches.

Through detailed analysis of video evidence, several unique patterns of smoke filling are observed. These include encapsulation of the fire in the burn room, a smoke hazing effect, visual evidence of a smoke layer within the smoke layer, and smoke layers that ascend from floor to ceiling. Due to their importance in the determination of visibility through a given escape route, these are worthy of more in-depth investigation in future research. Overall, the research fills key gaps in our understanding of the evolution of fire environments in limited ventilation residential furniture fires as related to available time for occupant escape. As such, it highlights the need for defined fire safety objectives in house design to improve residential fire safety.