Fire Scene Evidence Collection Guide

Ignitable Liquid Residue & Fire Debris

Stair Treads

Detailed Procedure:

If the treads are covered with carpet, follow the procedure for collecting carpet. If the stair treads are wood, follow the procedure below.

  1. Select a productive sampling area. Productive sampling areas include:

    • Within an area of ignitable liquid indicators, such as a suspected pour pattern

    • In an area where ignitable liquid may collect, such as the lowest point on the grade

    • Edge of a burn pattern or suspected pour pattern

    • At junctures with furniture and walls

    • Joints

    • Vertical grain

    • On stair treads at the joint between riser and tread

  2. Select appropriate new or properly cleaned tools, such as a chisel and mallet, to cut out the sample.

  3. Select a new, metal paint can container.

  4. Photograph the sampling area.

  5. Wear new, unused, clean latex or nitrile gloves.

  6. Use the chisel and mallet to break into the wood, preferably ½ inch on either side of the joint between the riser and the tread and up to the joint, as liquids tend to collect in seams. Break out a wood sample that includes the material in the seam and directly underneath the seam (include subfloor if possible).

  7. Place the sample in the paint can. If the sample is large, break it into smaller pieces to fit into the container. Make sure to leave 1/3 headspace in the can.

  8. Clean the lip of the can using a clean screwdriver or other suitable tool.

  9. Gently tap the top of the lid with a clean rubber mallet to seal it. Do not dent the can because it may compromise the seal.

  10. Seal the container with evidence tape. Initial and date the tape.

  11. If possible, collect a comparison sample from a location not within the ignitable liquid pattern and not in room of origin. Collect the comparison sample in a separate container using new gloves and a new or properly cleaned tool. A comparison sample for ignitable liquids testing will help the laboratory exclude compounds occurring naturally in the wood floor. This sample should be collected in a separate container.

  12. Label each container with identifying information, including case number, date, exhibit number, a brief description including recovery location, and your name.

  13. Store the item(s) in a secure location, such as a locked evidence van or your vehicle, until you are able to transport it to the laboratory.

Laboratory examination of stair treads for ignitable liquids:

Stair tread materials can be tested for ignitable liquids using gas chromatography mass spectrometry. This test can determine the classification of the ignitable liquid.

Source:

interFIRE. "Evidence Sampling for Ignitable Liquids Testing." Online Training Module, 2013:

http://www.interfire.org/training/evidencesampling.asp

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