STRUCK BY LIGHTNING AN INVESTIGATION
BY ARTHUR L. JACKSON AND PETER S. VALLAS
Since this month is the beginning of lightning season in the Northeast, we would like to relate a fire investigation we conducted involving lightning.
We were hired through our company to investigate the origin and cause of a fire in a two-story wood-frame dwelling. The structure`s peaked roof was covered with asphalt shingles. On arrival, we conducted an outside inspection of the premises. We observed some damage to wood-shingle siding just below the roofline. Below this area was the weather head for the electrical service cable. We made a mental note of it and continued our inspection.
In the rear yard, we saw the remains of a bed. The mattress and box spring were heavily damaged by fire. We examined other remains of bedroom contents that were present. We then placed the mattress on top of the box spring to see if the burn patterns matched up; they did.
After completing our walkaround of the structure, we entered the structure and followed the soot and heat patterns to a second-floor bedroom. A partial cleanup already had been done in the bedroom. However, an area of burning and charring was still visible on the floor. Remembering the size of the mattress and box spring as well as the burn patterns, we mentally placed the bed along the far wall above the area of charring. We examined a wall duplex outlet in this area, which revealed some internal arcing and fusing. By visualizing the bed along the wall, we placed the mattress burn area directly in front of the outlet.
We then examined the other second-floor bedrooms. In the bedroom to the left of the room of origin, we observed that the ceiling, which was gypsum board over framing, had been severely affected by heat. The nails attaching the gypsum board to the ceiling joists were pushed outward and clearly visible. We also saw some soot smudging around an electrical outlet on the same exterior wall as the damaged outlet in the room of fire origin. We removed the outlet cover plate and found no arcing or fusing. However, the inside of the outlet had heavier soot smudging, a clear indication that an electrical abnormality had occurred.
We then examined the bedroom to the right of the room of fire origin. it showed only slight signs of heat and soot in the ceiling, which we attributed to the fire in the adjoining room. The room`s duplex wall outlets showed signs of sooting and smudging but no arcing or fusing.
During our walkthrough of the dwelling`s interior, we looked for other possible ignition sources common to a single-family dwelling such as cigarettes and candles. We found neither candles nor ashtrays.
We inspected the basement area where the electrical distribution panel, gas-fired hot water boiler, and hot water heater were located. We found no areas of fire origin and eliminated all building utilities as possible fire causes.
After examining the fire scene, we interviewed the family members–a husband, wife, and the teenage daughter, whose room was the room of fire origin. We obtained the following information:
On the morning of the fire, a severe lightning storm had moved through the area. During the storm, the husband and wife were stunned by a lightning strike in close proximity to the house. Afterward, they reported the electricity was not working. The husband went to the basement and found that the main breaker in the electrical panel had tripped. He reset the main breaker, and the electricity came back on. The husband and wife then left for work. (The daughter had left for school shortly before the storm.) An hour or so later, a neighbor saw smoke coming from the house and called the police and fire departments. The neighbor also called the wife at work to tell her about the fire.
We discussed the layout of the daughter`s room with the family and confirmed the location of the bed. We also asked the following questions:
Did anybody in the house smoke? (No.)
Had any candles been used in the house? (No.)
Had there been any problems with an electrical appliance in the bedroom prior to the fire? (No.)
Had anything been plugged into the outlet alongside the bed? (No.)
We returned to the daughter`s bedroom to reexamine the outlet. We looked carefully at the outlet`s receptors and found no prongs left from an appliance. This confirmed that in all probability nothing was plugged into the outlet when the fire occurred.
As we stood in the bedroom, we put the pieces together: the damage outside the house above the electrical service cable, the tripping of the main circuit breaker, the damage to the electrical outlet in the room of origin, and the soot and smudging on other outlets on the same circuit.
We went to the attic area above the bedrooms. Searching with a flashlight, we discovered exactly what had happened. A bolt of lightning had struck the utility pole across the street. The surge followed the electrical service cable to the house and entered the attic. The magnitude of the surge caused a wooden stud inside the attic to explode and shatter. The bolt of lightning hit a nonmetallic-sheathed cable wire next to the stud. The bolt vaporized the bare copper ground wire between the insulated hot and ground wire in the cable. The surge traveled along the wire, damaged the outlet in the room of fire origin, and tripped the main circuit breaker. This explained the strange heat pattern on the ceiling of the adjoining bedroom located just below this area as well as the damage on the outside of the house.
The surge that damaged the outlet caused sparks and molten metal to strike the bed next to the outlet, causing ignition of the bed and the fire. In all probability, the bed was smoldering unnoticed when the husband and wife left for work.
It has been our experience that fires that cause only minor damage afford greater lessons in fire investigation. This is because as the fire progresses, it comsumes the items in the area of fire origin. As the fire grows larger, it causes structural collapse, causing further damage as well as hiding and altering the fire`s heat source. Whether it`s a fire caused by an appliance failure or an intentional fire started with the aid of a liquid accelerant, it usually is easier to make a determination if the fire is extinguished early and fire damage is kept to a minimum. More important, you can rely on the observations and lessons learned from the smaller fires when investigating the larger fires.
After our investigation we wondered, What if the roof and attic had been completely destroyed by the fire? Would we have found the wire that had been hit by lightning? Would we have found the duplex outlet in the room of origin? Hopefully we would have, but would we have overlooked the subtle signs of damage because of the absence of prongs? Unless there is a believable eyewitness to a fire, the rule “The more the damage, the harder it is to determine origin and cause” applies.
Remember, every fire is unique. Always keep an open mind until you have completed your investigation. And no matter how large or small the fire, use the same systematic approach to your investigation. n
ARTHUR L. JACKSON is chief fire investigator for Peter Vallas Associates, Inc., a Hackensack, New Jersey-based company that provides fire and explosion analyses, investigation, and engineering services. He also is a fire official and a 25-year veteran of the Hasbrouck Heights (NJ) Fire Department.
PETER S. VALLAS, chief executive officer, CFEI, CFII, of Peter Vallas Associates Inc., has more than 17 years of experience investigating industrial, commercial, and residential fire sites. He is an instructor for insurance companies, property adjusters, and fire investigators and lectures extensively.
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An outside inspection of the premises revealed damage to wood-shingle siding just below the roofline (top), which was located above the weather head for the electrical service cable (bottom). (Photos courtesy of authors.)
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(Left) The box spring from the room of fire origin, found in the rear yard, was heavily damaged by fire. (Right) Soot and heat patterns led to this second-floor bedroom/room of fire origin; the red arrows point to the burn patterns that indicate the location of the bed.
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(Above ) The second-floor bedroom/room of fire origin prior to cleanup and fire investigation. (Top right) The room after cleanup. The arrow points to the outlet, which showed some internal arcing and fusing. (Bottom right) A closeup of the outlet, which subsequently resulted in the bed`s ignition.
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The other second-floor bedrooms had signs of heat damage: An outlet in an adjoining bedroom had soot smudging (top), and nails attaching gypsum board to ceiling joists were pushed outward (bottom).
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A bolt of lightning caused a surge to follow the electrical service cable into the attic of the house. (Left) The surge`s magnitude caused this wooden stud in the attic to shatter. (Right) The bolt of lightning hit a romex wire next to the stud, vaporizing the bare copper ground wire.
