Fire Scene Evidence Collection Guide

Oils and Greases

Vegetable Oil Residues

Detailed Procedure:

Fires can be caused by the spontaneous ignition of vegetable or animal oils if the right conditions are met. These conditions include: an isolated fire; thick heavy smoke; usually a lengthy time frame of 2-48 hours; a box of rags, clothes, or other fuel load; and no other competent ignition sources. Suitable substrates to collect to test for vegetable oil residues (VOR) include absorptive materials, such as cotton rags, or similar type cloths and fabrics, filters, trash cans, cardboard boxes, laundry baskets, and flooring materials (wood flooring, carpet and padding).

Fire debris samples can be collected to determine if vegetable oils were present by testing for the presence of fatty acids and their tendency to self-heat. The presence of fatty acids may aid the fire investigator in determining a possible spontaneous heating ignition source.

What items should be collected and the specific collection procedure for items that may bear vegetable oils is influenced by the situation. Below are the most common types of situations where spontaneous ignition of vegetable oils may be considered as a potential cause and, therefore, evidentiary items possibly bearing these oils could be collected.

Clothes Dryers
To collect items potentially bearing vegetable oils from a clothes dryer:

  1. Select a productive sampling area. Try to collect intact, wet/moist cotton cloths. Avoid charred rags/cloths if possible.

  2. Photograph the fire debris in place.

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

  4. Because the debris may contain ignitable liquid residues or vegetable oil residues, it must be collected in an airtight container. If not confined in an airtight container, the ignitable liquid vapors may evaporate. Therefore, place the debris inside a new, unused, metal paint can of sufficient size. Leave 1/3 headspace in the can for vapors.

  5. Multiple rags can be placed in the same gallon can, not to exceed 2/3 of the container.

  6. A sample of the P-trap from the washer can also be collected for analysis.

  7. Comparison liquids, suspected of containing the VOR, should be collected in a glass vial, and labeled with the name and manufacture of the liquid.

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

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

  10. Store the container in a secure location (refrigerated, if possible) until you are able to transport it to the laboratory.

Trash Cans, Laundry Baskets, and Cardboard Boxes
To collect items potentially bearing vegetable oils from a trash can, laundry basket, or cardboard containers:

  1. Select a productive sampling area. Try to collect intact, wet/moist cotton cloths. Avoid charred rags/cloths if possible.

  2. Photograph the fire debris in place.

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

  4. Because the debris may contain ignitable liquid residues or vegetable oil residues, it must be collected in an airtight container. If not confined in an airtight container, the ignitable liquid vapors may evaporate. Therefore, place the debris inside a new, unused, metal paint can of sufficient size. Leave 1/3 headspace in the can for vapors.

  5. Try to collect intact, wet/moist cotton cloths. Stay away from charred rags/cloths if possible

  6. If a suspected trash can, laundry basket, or cardboard box is found, you may package the remnants in a gallon can or nylon fire debris bag.

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

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

  9. Store the container in a secure location (refrigerated, if possible), such as a locked evidence van or your vehicle, until you are able to transport it to the laboratory.

Restaurants and Massage Parlors
To collect items potentially bearing vegetable oils from a restaurant or massage parlor:

  1. Select a productive sampling area. Try to collect intact, wet/moist cotton cloths. Avoid charred rags/cloths if possible.

  2. Photograph the fire debris in place.

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

  4. Because the debris may contain ignitable liquid residues or vegetable oil residues, it must be collected in an airtight container. If not confined in an airtight container, the ignitable liquid vapors may evaporate. Therefore, place the debris inside a new, unused, metal paint can of sufficient size. Leave 1/3 headspace in the can for vapors.

  5. Collect any grease/oily-looking drippings using a clean paper towel or any sterile object and place it in an unused metal container.

  6. Comparison liquids suspected of containing the possible vegetable oil residues VOR should be collected in a glass vial, and labeled with the name and manufacture of the liquid.

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

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

  9. Store the container in a secure location (refrigerated, if possible) until you are able to transport or mail it to the laboratory.

Paint Booths
To collect items potentially bearing vegetable oils from a paint booth:

  1. Select a productive sampling area. Try to collect intact, wet/moist cotton cloths. Avoid charred rags/cloths if possible.

  2. Photograph the fire debris in place.

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

  4. Because the debris may contain ignitable liquid residues or vegetable oil residues, it must be collected in an airtight container. If not confined in an airtight container, the ignitable liquid vapors may evaporate. Therefore, place the debris inside a new, unused, metal paint can of sufficient size. Leave 1/3 headspace in the can for vapors.

  5. Collect the filter from the paint sprayer, if available. Place the used filter into a new, unused metal can.

  6. Collect an unused booth filter for a comparison sample. If an unused filter is not available, collect a filter from a similar paint booth. Place the filter to be used as a comparison sample into a new, unused metal can.

  7. Collect a comparison sample of the paint that has been sprayed, if available. Take a photograph of the paint can. Placed clean paper towels inside a quart or gallon new, unused metal can. Spray a couple of sprays onto clean paper towels inside the can. Seal the can immediately.

  8. Determine when the filter was last changed and the date of when the sprayer was last cleaned. Note this on the evidence documentation.

  9. Seal the containers with evidence tape. Initial and date the tape.

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

  11. Store the container in a secure location (refrigerated, if possible) until you are able to transport or mail it to the laboratory.

Flooring
To collect items potentially bearing vegetable oils from flooring:

  1. Select a productive sampling area. Try to collect intact, wet/moist cotton cloths. Avoid charred rags/cloths if possible.

  2. Photograph the fire debris in place.

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

  4. Because the debris may contain ignitable liquid residues or vegetable oil residues, it must be collected in an airtight container. If not confined in an airtight container, the ignitable liquid vapors may evaporate. Therefore, place the debris inside a new, unused, metal paint can of sufficient size. Leave 1/3 headspace in the can for vapors.

  5. Collect a suspected sample of flooring, including hard wood floors and/or carpet and padding, following the evidence collection procedure for that item.

  6. If possible, collect a comparison sample of the same flooring from another room outside the room of origin.

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

  8. Label the containers with identifying information, including case number, date, exhibit number, a brief description including recovery location, and your name.

  9. Store the containers in a secure location, such as a locked evidence van or your vehicle, until you are able to transport it to the laboratory.

Laboratory testing of vegetable oils:

Laboratory analysis can determine if vegetable or animal oils were present and their possible contribution to the fire. However, this is a specialty fire debris test that is destructive, therefore it is vital you communicate with your laboratory when vegetable or animal oils are suspected to have contributed to a fire.

Sources:

Gambrel, A.K., and M.R. Reardon. "Extraction, Derivatization, and Analysis of Vegetable Oils from Fire Debris." Journal of Forensic Sciences, 53 (6), 2008: 1372-1380.

Hibbard, R., J.V. Goodpaster, and M.R. Evans, "Factors Affecting the Forensic Examination of Automotive Lubricating Oils." Journal of Forensic Sciences, 56 (3), 2011: 741-753.

Reardon, M.R., L. Allen, E.C. Bender, and K.M. Boyle, "Comparison of Motor Oils Using High-Temperature Gas Chromatography-Mass Spectrometry." Journal of Forensic Sciences, 52 (3) 2007: 656-663.

Schwenk, L.M., and M.R. Reardon. "Practical Aspects of Analyzing Vegetable Oils in Fire Debris." Journal of Forensic Sciences, 54 (4), 2009: 874-880.

Stauffer, Eric, Julia A. Dolan, and Reta Newman. Fire Debris Analysis. Academic Press, 2007: Chapter 14, pp. 529-546.

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