The Pour Pattern and the Standing Water
At 05:15 firefighters finish extinguishing a bedroom fire in a 1970s single-family house. One adult is dead on the floor beside the bed; the family dog died in the hallway. The fire was confined to the bedroom, with heavy charring at the base of the closet, a V-pattern up the wall above it, and a burned area on the carpet that the captain calls 'a pour pattern'. The window was closed and intact, the door open. Suppression used roughly 1,200 gallons; there is standing water and floating debris across the floor. The coroner is 90 minutes away. The insurance adjuster has asked when the house will be released, and a family member wants to retrieve medication from the bedroom. You have one technician with you.
1. What must be established before you enter, and how do you handle the body and the family member's request?
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Before entry: the incident commander must declare the structure safe. Then monitor the atmosphere - carbon monoxide, hydrogen cyanide, and lower explosive limit - and ventilate before anyone works inside without respiratory protection. Check the floor and ceiling for structural loss, and confirm the electrical service is locked out. PPE: helmet, boots, gloves, eye protection, and P100 respiratory protection.
The body: do not move it until the coroner or medical examiner arrives, even at the cost of 90 minutes. Photograph it in place with scale, record its position relative to the door, the bed, and the burned area, and note the pugilistic attitude and any soot around the mouth and nose - but do not interpret airway soot yourself; that is the pathologist's finding. Cover the body only if there is a genuine risk of disturbance, and document that you did.
The medication request: refuse access to a scene, and explain why. If the medication is life-sustaining, an officer or the ME's investigator can retrieve it later with documentation. The adjuster gets nothing until release. Meanwhile, document the exterior, windows, doors, and every pattern visible from the doorway - you will destroy floor soot and debris with your first steps.
2. The captain calls the carpet burn 'a pour pattern'. How do you evaluate that claim?
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Treat it as a hypothesis to be tested, not a finding to be photographed. The floor is covered in standing water and floating debris after 1,200 gallons, so the surface is already disturbed; photograph the full pattern and its surroundings first, then work inward.
Alternatives to eliminate: a clean burn from a fuel package adjacent to the area; ventilation-limited burning after flashover, which can produce irregular, deep, floor-level damage that mimics a liquid; melted synthetic carpet and padding that pools and produces a rounded shape; a protection area where furniture shielded the floor. The V-pattern points to an origin near the closet base, and the carpet stain may be downstream of that origin rather than the origin itself.
Tests: the edge character (sharp and irregular versus smooth and diffuse), depth of char into the subfloor, evidence of a trail or pooling at a low point, a hydrocarbon detector reading, an accelerant canine if available, and laboratory samples. 'Pour pattern' should be the conclusion of last resort, reached only after ventilation and fuel-load effects are excluded. Tell the captain you will test the hypothesis rather than record his label as fact, and note his observation in your report as an observation.
3. Design the ignitable-liquid sampling plan for this room.
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Where: the lowest point of the burned area, where liquid would collect; the carpet seam and tack strip, which trap residue; the base of the closet, which the V-pattern identifies as the likely origin; and the subfloor beneath the damaged carpet, because water may have washed the surface residue downward. Sample porous material, not the char crust.
Comparison: take a sample of the same carpet and pad from an uncontaminated area - ideally an adjoining room or the far side of this one. Substrate pyrolysis produces the same compounds you are looking for, so a comparison is what makes the result interpretable. Collect the comparison with clean tools and change gloves between every sample.
How: approved metal cans or certified vapour-tight bags, filled one-third to one-half, sealed and labelled with location and item number. Never reuse a tool without cleaning, and never sample the same spot twice. Document the water level and the suppression sequence, because water dilutes and redistributes residue and the defence will raise it.
Collect before the room is ventilated further or cleaned, and note that the dog in the hallway is a possible transfer source if you later sample there.