Fire Consequences

“In just four minutes, a sofa fire can engulf an entire room in flames, filling the home with thick, dark smoke and toxic gases. Temperatures can exceed 1400°C in this short period of time[1]

Flashover

A burning non-fire safety treated sofa can result in peak heat releases of 2000 … 3000 kW (equivalent to two to three thousand electric bar-fires) and temperatures of 2000 °C in the flame plume [2], for example reaching heat releases of 1500 kW after 4 minutes and 3600 kW after 6 minutes [3].

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US National Fire Protection Association

Flashover in a full-scale room fire test :
Swedish National testing and Research Institute (SP) www.sp.se/fire

Such heat releases will result in “flashover” within minutes in domestic rooms – this means the fire, gas and smoke in a room reaches a high enough temperature for all combustible materials in the room to ignite (around 600°C). Death of room occupants is therefore inevitable [4].

Smoke and Toxic Gases

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However unsavoury the thought is - have you ever envisaged what a fire would be like in your own home? A popular misconception is that one might cough oneself awake on the acrid fumes or would even be woken up by the sound of breaking glass during the night.

The reality is that carbon monoxide gas is the major killer in fires. It is colourless, odourless and tasteless and can be very effective in causing deeper and deeper narcosis, rendering people sleeping in a house at night unconscious before the fire awakens them. This can happen at some distance away from the fire source in the house, even if the fire has already burnt out with only minor visible fire damage in the room it started in.

Besides carbon monoxide, hydrogen cyanide (HCN) is a narcotic gas emitted in significant quantities during any dwelling fire. Its concentrations in smoke can lead to irreversible health effects after a very short exposure, and can be deadly within minutes.

Dioxins and furans are complex products formed in relatively low quantities but can also have long term effects on health and the environment. They are formed during any uncontrolled fires, especially accidental fires.

Polycyclic aromatic hydrocarbons (PAHs) are typical incomplete combustion products which dominate the long-term toxicity of soot.
Irritant or corrosive gases are also contained in the smoke, such as sulphur oxides (SOx), nitrogen oxides (NOx), hydrochloric acid (HCl) or aldehydes.


How to reduce the toxicity of accidental fires

These toxic emissions from fire can be considerably reduced if consumer goods and building materials are flame retarded, because their rate of burning is reduced. This has been clearly demonstrated in a number of full scale fire tests.

A detailed study carried out by the US National Institute of Science and Technology (NIST) in 2004 [5], looking at different scenarios for development of fires in domestic buildings, shows clearly that smoke and gas emissions from smouldering items remain lower in order of magnitude, than emissions from the same items when flaming fire develops.
Flame retardants prevent or slow the development of flaming fire conditions.

Savolainen, 1998 [6], in a study of smoke toxicity, indicates that the use of flame retardants in polyurethane foam (PUR) and expanded polystyrene (EPS) building materials prolongs the delay before LT50 toxicity is reached; quantities of smoke from rigid polyurethane are lower or similar when flame retarded or not; and that flame retardants in cellulose fibres reduce smoke emissions in a dose-related fashion.


1 National Association of Fire Marshals http://www.firemarshals.org/issues/home/upholstery_fires.html
2 DeHaan “Our Changing World: Fires, Fuels, Investigations, and Investigators” http://www.interfire.org/features/ourchangingworld.asp

3 US National Institute of Science and Technology, NIST, Heat emission 1500 kW - 5 minutes after ignition of a standard sofa – photo National Institute for Science and Technology NIST USA http://www.fire.nist.gov/fire/fires/sofa/sofa.html

4 Flashover: description see http://www.fire.org.nz/facts_stats/science/science.htm

5 NIST July 2004 (Revised 2008) 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

6 Heikki Savolainen, Nicolas Kirchner: Toxicological Mechanisms Of Fire Smoke. The Internet Journal of Rescue and Disaster Medicine. 1998. Volume 1 Number 1 http://www.ispub.com/ostia/index.php?xmlFilePath=journals/ijrdm/vol1n1/smoke.xml

 
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