A fire investigation at the end of a long day was a perfect illustration of staying open to potential causes, and, a reminder that sometimes discovering the origin and cause of a fire is a life-saving endeavor when it prevents future dangers.
The fire was on the exterior of the building, which was covered with vinyl siding (at least partial siding, since much of it had melted away). The fire involved the exterior wall near the heating, ventilation, and air conditioning (HVAC) unit. I was curious about whether the fire involved the large number of needles from the overgrown pine tree covering the yard, or the potential that the natural gas from the nearby meter had contributed to the fire. I noted that the gas meter was operational, and had not been pinned in the "locked" position. The homeowner advised that the utility company responded during the fire incident at the request of the local fire department, and the meter was left intact, noting no need to isolate the meter.
I took the opportunity to explain to our quality assurance specialist our process of fire scene reconstruction and keeping an open mind to potential causes. While piecing together the pieces of vinyl siding to identify the fire patterns and potential area of origin, I lightly disturbed the pine needles against the wall. I briefly thought I smelled natural gas, which can migrate through soil if it is the path of least resistance. Although natural gas is lighter than air and will usually dissipate, I changed my focus to consider an alternate hypothesis involving the potential of migrating gas being ignited by the HVAC unit. Then, my partner for the day also smelled gas. We stopped what we were doing to further question the occupant, who gave us more details on the response of the utility company. We called the utility company and did some further checks around the house.
It turns out, the gas leak was inside the wall and spread inside the home. We could smell it outside since there were several wall penetrations created during the fire and subsequent suppression activities. A corrugated stainless steel tubing line inside the wall had been compromised by the heat from the fire, and the operational gas meter gave no obvious indication of leaking gas into the house. The homeowner confirmed that she smelled gas earlier that afternoon, but disregarded it in passing. The responding technician from the utility company checked the meter and verified a leak beyond the meter, since pressure was being lost inside the house. The meter was then safely secured.
Eventual replacement of the vinyl siding may not have led to the discovery of the leaking gas, and the potential for a catastrophic event in the future was possible. Gas explosions happen occasionally, and you never know when your actions will involve a potential life-saving decision.
DONAN, a family owned company founded in 1947, provides full-service Forensic Engineering and Fire Investigation Services. For over 60 years, Donan Engineering has been providing unbiased answers to their client's complicated questions. Their team of licensed and experienced forensic experts provides investigative services in the fields of engineering investigations, fire and explosion origin & cause, roofing investigations, and component testing. The diversity of their multidisciplinary staff allows them to provide not only a complete service, but a complete service whose conclusions can be successfully and completely supported.
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