Study of Technology for Detecting Pre-Ignition Conditions of ... - NIST

Executive Summary
CPSC-LAG-95-1145
A significant portion of residential fires stem from kitchen cooking fires. Existing fire
data indicate that cooking fires primarily are unattended and most often involve oil or grease.
The purpose of this investigation was to ascertain the existence of one or more common features
or characteristics of the pre-ignition environment that could be used as input to a sensor in a prefire
detection device, The ultimate goal of this continuing study is to evaluate the feasibility of
incorporating such a device into the range that would react to a pre-fire condition and reduce the
occurrence of unwanted kitchen fires.
The focus of the study was unattended foods placed in pans on burners set to high heat.
Experiments were conducted with three different foods and with gas and electric ranges to
investigate the pre-igniti,on environment of actual range-top cooking fires. Numerous
temperatures in the near surroundings as well as local plume velocity and laser-attenuation
measurements were recorded. A Fourier transform infrared spectrometer was used to observe
significant species production above the food. Results of these experiments are presented and
evaluated.
The second part of this study was a literature and patent search of technologies with the
capability to act as either the sensor in a pre-fire detection device or as the automatic control that
would respond to a detectcr warning signal by shutting off the gas or electricity supply. A broad
range of potential detection technologies was reviewed because the pre-fire signatures had not yet
been identified. A bibliography and comments on the applicability of different technologies are
included.
The conclusions pertaining to the experiments are based on measurements and
observations of combinations of specific ranges; pans, foods, and ventilation so extrapolation to
other conditions should be performed with caution. The major conclusions of this research are
as follows:
● Strong indicators of impending ignition were temperatures, smoke particulate, and
hydrocarbon gases.
● Promising detection technologies include: tin oxide (Sn02) sensors for hydrocarbon
detection, narrow band infrared absorption for hydrocarbon detection, scattering or
attenuation types of photoelectric devices for smoke particle detection, thermocouples for
thermometry of the burner, pan, range surface (top and below), or range hood.
● Logical processing of signals from two or more of the detection technologies could be an
important means by which false alarms of pre-ignition conditions are eliminated.
● Control technologies exist that are applicable to the safe shutdown and restart of gas and
electric ranges upon detection of approaching ignition.
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