Escape times in domestic fires have dropped drastically
The time available between a fire starting in a home and escape becoming impossible has fallen drastically over the last 30 years, according to a recent study by NIST. The increasing fire load in homes, from consumer products, furnishings and decorations, is a major cause.
A 2005 study by NIST (US National Institute for Science and Technology) shows that “escape times” (time between start of a fire and reaching untenable conditions or flash over) have dropped drastically, from 17 minutes in 1975 to 3 minutes today (2004).
The study was looking at the location and performance of different types of residential smoke alarms (fire alarms), and was based on laboratory tests, modeling, and two full scale tests in actual residential structures with representative sizes and floor plans, using actual furnishings and household items for fire sources.
The present work followed a design similar to that used in the 1975 « Indiana Dunes tests », sponsored by NIST (then the National Bureau of Standards) and conducted by the Illinois Institute of Technology Research
Institute and Underwriters Laboratories, allowing comparison between the 1970’s and today’s situation.
Additionally a separate study of nuisance alarm sources was conducted because this was identified as an important issue in a prior study by the U.S. Consumer Product Safety Commission.
Furniture and mattresses
The study included an analysis of residential fire statistics. Flaming and smoldering upholstered furniture and mattresses account for the top four most deadly fire scenarios.
Test results confirmed this, with fire tests on both (non flame retarded) chairs and mattresses reaching “untenable conditions” (such that escape for room occupants had become impossible) after just 3 minutes.
The possibility for occupants of a residential structure to escape was assessed by modeling (based on real fire test data), parameters including fire heat, flames, toxic gases (in particular, carbon monoxide CO).
Fire load of consumer products and reduced escape time
The study report conclusions state: “Escape times in this study were systematically shorter than those found in a similar study conducted in the 1970’s. This is related to some combination of faster fire development times for today’s products that provide the main fuel sources for fires, such as upholstered furniture and mattresses, different criteria for time to untenable conditions, and improved understanding of the speed and range of threats to tenability.” This thus confirms that the increasing fire load of consumer products and home decorations is effectively making home fires increasingly dangerous, to a point where fire alarms sounding will often not provide adequate time for occupants to escape. Flame retardants, to slow fire spread and development, are thus increasingly critical.
3 minutes escape time Smoke alarm installation in US homes rose from around 10% to 95% over this period. The study again proved their value in saving lives by enabling occupants to escape, but showed that even if smoke alarms are installed and operational, escape times can be very short because of household contents’ fire load. The escape time, when alarms are installed, in the scenario of a flaming fire, is just 3 minutes.
The addition of smoke alarms in bedrooms showed to be important, particularly for smoldering fires.
Positioning of alarms away from cooking areas can reduce nuisance alarms, which are often related to cooking activities.
All data collected in the tests is freely available at LINK TO REPORT
Full study report: NIST July 2004 study, Bukowski, R.W. et al.. “Performance of Home Smoke Alarms,
Analysis of the Response of Several Available Technologies in Residential Fire Settings” NIST Technical Note 1455 (396 pages) http://smokealarm.nist.gov/HSAT.pdf
Residential building test data: http://smokealarm.nist.gov/Series2.htm
Summary of 2004 report in Canadian Fire Alarm Association journal “Three minutes espace time”: http://www.cfaa.ca/journal-2004-summer-escape.pdf
1975 study: Bukowski, R.W., Waterman, T.E:, and Christian, W.J. Detector Sensitivity and Siting Requirements for Dwellings: A Report of the NBS “Indiana Dunes Tests”. NFPA No. SPP-43. Nat. Fire Prot. Assn., Quincy, M