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Fire Scene Evidence Collection Guide

Fuel Gas Systems Equipment

This section details how to properly locate, document, collect, label, package, store, and preserve gas piping during fire scene evidence collection and for subsequent use in testing or legal proceedings. 

A wide array of fuel gas systems equipment, components, and products may be present at a fire scene, including piping, valves, and appliances. Fuel gas systems equipment is often examined by an expert with specialized experience. The evidentiary value of fuel gas systems equipment may be compromised if not collected properly. Do not attempt to operate fuel gas systems equipment or products obtain information from them in the field. If you have questions or concerns about a particular fuel gas systems component, consult your laboratory prior to touching the device. 

Remember to photograph and document the fuel gas systems equipment in place prior to collection. Follow the procedures in this section to implement fire scene evidence collection best practices for fuel gas systems equipment. If you are unsure which fuel gas systems fire scene evidence collection procedure to use or do not have sufficient experience to execute the procedure, consult your laboratory prior to collection.
Remember to also review the Checklists prior to collection and prior to releasing the scene.


Detailed Procedure

Prior to entering the fire scene, don appropriate PPE.

To collect gas piping:

  1. Evaluate and test the gas supply system to ensure it is void of gas and safe to collect evidence.  Visually inspect the service and test with a gas detection meter as appropriate.

  2. Conduct a pressure test for leaks prior to cutting or removing components.

    1. ​Prior to pressure testing, isolate the system according to industry standards.

    2. Test according to industry guidelines such as NFPA 54 and/or 58 or EPA testing protocols.

    3. If checking for leaks on site, use gas leak detection fluid or a soap/water solution.

  3. Sketch or diagram the scene, including all gas-fired appliances, and evidence to be collected, noting the gas line of interest and which appliances it serviced.

  4. Document all aspects of the gas distribution system including regulator, pressure, meter, supplier, and other information. If the system is connected to a local system, such as an on-site propane distribution system, document all components associated with local system, including regulator, storage tank, and other information.

  5. When you are ready to collect, don new, unused, clean latex or nitrile gloves and gather the containers and tools necessary. Typically, boxes or zip plastic bags are used. A hack saw, band saw, or reciprocal saw will be needed.

  6. Apply a tester to the gas pipe as a presumptive test for the presence of gas. If gas is not present, proceed.

  7. Use the general to specific methodology to photograph the gas pipe in place. Continue photographing the collection process as you collect the pipe.

  8. Locate the area of interest in the gas system. If the gas supply service of interest is in debris, carefully excavate the entire length of the service in the area of interest and document accordingly.

  9. Use a paint pen or permanent marker to make witness marks on all connections and fittings.

  10. Make witness marks on any valves to denote position.

  11. Note line side vs. load side to document flow direction.

  12. Make witness marks on the area of the gas supply service pipe to be cut or detached.

  13. Continue to mark fittings on all parts of the gas pipe.

  14. Use a hack saw, band saw, or reciprocal saw to cut the gas pipe between the witness marks for the section to be removed.

    1. ​NFPA 921 recommends cutting the service line as the preferred collection method.  In some cases, it may be acceptable to remove the section of interest at fittings or unions outside the area of interest.

  15. If the service line is secured to the framing with U clamps, either pry loose or remove screws securing the clamps to free the section being collected.

  16. Remove the gas pipe segment of interest.

  17. Use zip ties or a similar method to secure the pipe to a backer board to prevent damage or alteration, specifically to the position of the valves and fittings.

  18. Wrap the backer board with cellophane self-sealing plastic membrane to protect the pipe.

    1. ​A zip bag may also be used as a container.

  19. Press the cellophane to seal the edges.

  20. Label the cellophane wrap with case information according to your organization’s SOP.

  21. Seal the packaging with evidence security tape on all four sides.

  22. Initial and date the tape. 

  23. Ensure that the cut line is capped and gas is not flowing to it.

  24. Store the collected items in a secure location until you can transport them to the laboratory.

  25. Transport the collected items to a climate-controlled, secure evidence storage facility consistent with your organization’s guidelines. If you will be shipping the evidence to a lab, consult the lab for advice on how to package for shipping so the evidence is not damaged in transit.

Laboratory testing of gas piping:

Examination of gas in a laboratory environment may provide an opportunity to evaluate and document potential failures with the assistance of light microscopy, x-ray, computer tomography, metallurgical evaluation, or SEM/EDS analysis.

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