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Spontaneous Ignition in Fire Investigation

NCJ Number
Date Published
April 2012
69 pages
This scientific description of spontaneous ignition and an associated theory provides the fire investigator with the knowledge needed to determine whether such ignition has occurred.
Spontaneous ignition is initiated through heat transfer or the inability to cool a hot material. The process starts as a chemical reaction that is not yet combustion; the consequence of ignition can be smoldering or flaming. The key variables involved in this process are the size of the material and the nature of the heat transfer, as well as the particular chemical and physical properties of the material. In any fire investigation, it is important for the investigator to recognize the signs of spontaneous ignition and to learn how to estimate whether it was possible in the particular fire pattern. This requires collecting samples for measurement. It is also important for forensic laboratories to have the capability and understanding to perform tests that can determine whether spontaneous ignition has occurred. Three scenarios for spontaneous ignition are considered in this report: a cold material in hot surroundings, a material on a hot surface, and a hot material in cold surroundings. A survey of just over 200 investigators inquired about their experiences with spontaneous ignition. Most of the incidents of spontaneous ignition reported involved materials infused with linseed oil, wet hay storage, and problems with clothing just taken from a dryer. Other cases involved potting soil, mulch, and a variety of other materials. The current study focused on linseed oil and cotton. The properties needed for spontaneous ignition were measured with two methods. The testing required a specialized oven. The two testing methods are described. Examples are provided on how to use the material and a technique for measuring the heat transfer coefficient of the oven. A database of property data was compiled. 4 tables, 10 references, and a listing of nomenclature

Date Published: April 1, 2012