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House Fire - Candles v. Natural Gas - Fire Investigation

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Michael Fox, PhD.

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E-mail: service@chemaxx.com

 

house fire

SEARCH

CHEMAXX HOME

Areas of Expertise

Michael Fox, PhD.

CONTACT US:
800-645-3369

E-mail: service@chemaxx.com

House Fire - Candles v. Natural Gas

A family woke up at 6:00 a.m. on the day after Christmas to find their home in flames. A mother and child were trapped inside the downstairs master bedroom due to a lock that had been placed on the sliding glass door to the outside patio deck. This lock required a key to open it from the inside. Therefore she could not escape. The mother was seriously burned and the child also, but to a lesser degree (the mother covered the child with her body). The husband was also seriously burned when he tried to rescue his wife and child. The husband had been sleeping in an upstairs bedroom while the wife and child were sleeping in the downstairs master bedroom. The husband was seriously burned over 60% of his body and was in a coma for many months. The Chemaxx role is to investigate two fire origin scenarios, kitchen versus family room.

The family room had a classic V-Pattern on one wall that was made from cedar wood paneling, indicating that the origin was in the family room near this wall. Witnesses had seen candles in this vicinity prior to the fire. It was the Christmas Holiday Season and candles are often involved in fires during this time of year.


Family Room V-Pattern
A second scenario for the fire origin was that the fire started with a leak in a natural gas range in the kitchen, and that the V-Pattern in the family room was created by ventilation from a furnace vent located at the base of the V-Pattern. The furnace was an old downdraft style and the heating ducts ran under the house in a crawl space and emerged near the baseboards.

In a lengthy and detailed investigation of both scenarios, Chemaxx performed numerous tests that included:

Site inspections
Crawl space inspections
Removal of old heating ducts from crawl space
SEM/EDS of deposits in old heating ducts
Heating tests on duct tape removed from the old heating ducts
Heating tests on flexible heating ducts
Simulations of gas leaks and fires in an exemplar natural gas range
Measurements of gas concentrations from a simulated leaking gas range
Heating and melting tests on a plastic smoke detector from the house
Simulated heating tests on an exemplar down-draft gas furnace
CFAST Computer Fire Modeling
FDS and Smokeview Computer Fire Modeling
Scanning calorimetry on cedar wood paneling

Experiments on an exemplar gas range demonstrated that a fire inside the gas range could not spread to surrounding structures. In other words, any gas flames inside the range would stay inside the range.

This was
determined
by lengthy experiments
on an identical exemplar gas
range that was installed in a
special re-created kitchen, shown here.

All types of leaks were explored.


Re-created Kitchen
Furthermore, when a gas leak inside the gas range was ignited by the pilot light, both the pilot light and the gas flames blew themselves out, leaving behind no fire. A slow leak would not ignite and a leak fast enough to ignite blew itself out. Starting a fire inside the gas range required very special and unnatural procedures. A continual gas leak into the kitchen (without a fire) would have resulted in a gas explosion, which did not happen. There was no gas explosion associated with this fire.

Another finding was that a fire in the kitchen was unlikely to turn on the heating furnace. Since the fire occurred in December, the thermostat was set to go on if the temperature dropped, not increased. Additional experiments on an exemplar furnace showed that the furnace fan would turn itself off if the air flowing through the furnace exceeded 150 F. Therefore, even if a fire started in the kitchen, it is unlikely that the furnace could have facilitated any ventilation-induced V-Patterns in the family room. The furnace fan would have turned itself off well before the fire spread to the family room.

Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) on samples removed from the heating ducts from under the house did not show any evidence of soot or elevated temperatures, which would have been present if the furnace circulating fan had run during the high-temperature fire.

Heating and melting experiments were also conducted on the duct tape removed from the heating ducts from under the house as well as flexible ducting. Those heating and melting tests also confirmed the absence of heat in the furnace ducts during the fire.


Some of the Heating Ducts Removed from Underneath the House

Such absence of heat was inconsistent with the furnace fan running during the fire. There was only one air intake for the furnace, and it was located in the kitchen near the ceiling. Hence a fire in the kitchen would have put very hot air (1100 F) into the furnace system, if in fact the furnace system were running.

Computer fire modeling by both CFAST and FDS Smokeview supported the conclusion that the fire started in the family room where the V-Pattern was located.

The computer models were calibrated against thermal damage found on various objects and in different rooms or compartments.
For example, heating experiments on a plastic smoke detector determined the maximum temperature reached at that smoke detector, which was located in a nearby room.

Smoke Detector
Smoke Detector Used to Calibrate Fire Computer Models
Additionally, the computer models included a coat closet in which the thin plastic coverings on clothes recently brought home from the cleaners showed little heat damage. Benchmarking the computer models against these types of known materials and experimentally determined maximum temperatures added credibility to the temperature profiles generated by the computer models. Agreement between the computer models and actual fire damage was about as good as could be expected from any computer model.

The multi-million dollar litigation against the natural gas company that prompted this investigation settled prior to trial.

Dr. Fox is a fire expert, explosion expert and chemical expert with extensive experience in OSHA chemical regulations and chemical safety.