In 2009, the National Research Council (U.S) published a report identifying the research needs of the forensic science community. In the field of fire investigation, one of the specific needs identified was research on the natural variability of burn patterns. The National Institute of Standards and Technology (NIST) is conducting a multi-year study, with the support of the National Institute of Justice (NIJ) and the NIST Office of Law Enforcement Standards (OLES), to examine the repeatability of burn patterns. The primary objective of the study is assessing the repeatability of burn patterns on gypsum board exposed to a range of source fires. This paper will provide the results from the characterization of the source fires and the results of the pre-flashover fire pattern repeatability experiments. Experiments were conducted with a natural gas fueled burner, a gasoline fueled pan fire, and polyurethane foam. The top surface of the burner or fuel was 0.30 m (1lft) by 0.30 m (1 ft) with the top surface approximately 76 mm (3 in) above the floor. Replicate source fire experiments were conducted in a oxygen depletion calorimeter with each of the fuels, in order to examine the repeatability of the fires in terms of heat release rate. The flame movement and height for each fire was recorded with photographs and videos. The fire pattern experiments were conducted in a three-sided structure with a full floor and partial ceiling was constructed from wood framing and lined with painted gypsum board. The source fires were positioned against the rear wall, midway along its length. Replicate experiments were conducted with each fuel. A new piece of painted gypsum board was used for each experiment. The burn patterns were documented and analyzed for repeatability. The results are presented in terms of the fire pattern height, width, and total area.
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