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Most people have a reasonable and common sense idea of what fire is. However, when interpreting the wording on an insurance policy or litigating a fire loss in the courts, a firm and conclusive definition is required.


One of the most accepted definitions of fire is put forward by the National Fire Protection Association as…" a rapid oxidation process with the evolution [generation] of light and heat in varying intensities". In short, if a fuel is being oxidized at a fast rate and there is heat and light or a glow being generated by the reaction, it is a fire.

Oxidization is a chemical process where a material or fuel combines with oxygen and is consumed in the production of other materials. For a fire to be possible, this process must happen at a rapid rate. The formation of rust is an oxidization process but cannot be considered as a fire as the process is slow and no light is being generated by it.

This oxidation process must also be continuous and unrestricted. In the past, the term "fire triangle" was used to describe the three elements thought to be required for fire to happen: fuel, oxyggen and an ignition source or heat. Additional research has recently expanded the triangle to the "tetrahedron of fire" with uninhibited chain reactions making up the "fourth side". Take away one or more of the fire tetrahedron's sides and you don't have a fire.

By definition, there will be heat and light generated by any fire, whether it is a raging inferno or a small smouldering fire in a cigarette tip. The issue of light generation or "glowing" associated with fire has come into play in several recent court cases in Atlantic Canada. In trying to decide if a fire has actually occurred, it has been put forward that an observer in the area of the "incident" would have likely seen a glow associated with the incident and a glow or light generation indicates a fire. The presence of a glow is not, in itself, indicative of fire, as per the accepted definition. Most materials will glow if heated to a hot enough temperature but they may not be burning. A good example of this is the heating up a sewing needle in a candle flame. The needle will glow red-hot when removed from the flame but it most definitely is not on fire.

In response to the question asked in the title, smoke does not necessarily indicate fire and a fire does not necessarily generate smoke. A review of the definition shows that smoke is not a requirement for a fire to occur and is not an indicator of fire. Smoke is a particulate product of incomplete combustion or burning. So if the fire is burning very efficiently (such as in a natural gas burner), no visible smoke may be generated merely by heating most materials to a temperature lower than their ignition or burning point. A good common sense example is deep frying oil on the stove. The oil, if overheated, will smoke extensively well before it actually bursts into flaming combustion.

Walters Forensic Engineering was recently involved with a civil legal action surrounding a chicken barn loss where the definition of fire was the key to the case. The plaintiff from owner maintained that the loss was doe to a fire at a control system switch due to the likely presence to smoke, glow and melting a the switch. Walters Forensic Engineering acting on behalf of the insurer, stated that while there was damage at the switch, the damage was the result of a prior electrical failure, which negated any coverage for the loss. In granting a dismissal of the action against the insurer, the trial judge relied solely on the expert testimony given at trial and based his final judgement on a correct interpretation of the definition of fire, the very same definition given in this article.

Walters Forensic Engineering is well versed in current and up-to-date fire investigation techniques including the use of NFPA 921 and computer fire modelling.

The information contained in this web site is intended for marketing purposes only. It is not all-inclusive, and does not fully describe the many and varied services that the company provides, nor does it completely describe the education, training, skills, or expertise of our staff.


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