FIRE INVESTIGATION: YOU CAN LEARN FROM FIRE
BY ARTHUR L. JACKSON
On a Sunday night in May 1993, an alarm of fire was received for a residence in Hasbrouck Heights, New Jersey. The weather was clear, with a temperature of 65°F. On arrival, the Hasbrouck Heights Fire Department found smoke emanating from the roof eves. The engine took the nearest hydrant as per departmental SOP. The fire was located under the aluminum siding near the roof line. The members extinguished the fire and opened some interior walls to check for fire extension. Then they turned the dwelling over to fire investigators from the Fire Prevention Bureau to determine origin and cause.
The initial investigators took statements from the two people who were home at the time of the fire–a middle-aged woman, who owned the dwelling, and her teenage daughter. Then the investigators examined the fire damage. All burn and char patterns indicated the fire originated below the aluminum siding and outside the exterior wall. They checked the area carefully but could not find an ignition source for the fire. Because the fire`s point of origin was approximately eight feet above ground level and the investigators detected nothing suspicious, they labeled the fire “accidental undetermined”; further investigation would be required.
INVESTIGATING CAUSE
The following day Lieutenant Ken Kubler and I continued the investigation. The homeowner was at home, and her daughter was in school. I explained to the homeowner that we had returned because we were unable to determine the ignition source for the fire. We interviewed her again to determine what she and her daughter were doing the night of the fire.
The homeowner told us the following: She was watching television in the living room and her daughter was upstairs in her bedroom. The electricity in part of the house went off. She went to the basement and found that a circuit breaker had tripped. She reset the breaker, the lights went back on, and she thought everything was okay. A short time later, she and her daughter smelled smoke. They found smoke coming from the roof of the house and called the fire department.
At this point in the investigation, we knew that the most likely ignition source was electrical. However, the initial investigators knew this as well and already had checked the previous night all exterior electrical wiring, outlets, light fixtures, and electrical service cable, which was cloth-covered service entrance cable. The local utility company also was called in to check the incoming electric service cable, meter, and meter pan enclosure.
After checking all these possibilities, we still could not come up with a cause. We asked to speak to the daughter again.
When the daughter returned from school, we asked her to take us up to her bedroom and show us what she was doing prior to the circuit breaker`s tripping. She told us the following: She was on her bed listening to the radio. It was getting cool, so she decided to unplug a fan in her room. She reached over and grabbed the wire end of a multiplug power strip and pulled it along the floor toward her. It was then that the lights went out.
We told her that no multiplug power strip was found in her room the night of the fire; she also failed to tell the initial investigators about it. She said that in all the excitement she forgot about it and did not think it was important. She said that after the circuit breaker was reset, she disconnected the power strip and put it in her closet. We asked her to retrieve the power strip. We then set up the power strip and power cords as they were on the night of the fire.
On the floor near (but not plugged into) the power strip was an extension cord for a window air-conditioner in the room. The extension cord was a heavy-duty cord suitable for an air-conditioner and had three wires in it: a hot wire, a neutral wire, and a ground wire. The molded male plug end of the extension cord had the ground wire extending from it, ending with a metal horseshoe connector. We examined the extension cord and found nothing unusual. The extension cord still was plugged into the window air-conditioner power cord. We then examined the multiplug power strip and found nothing unusual. We then checked the room fan, which the daughter was using the night of the fire. The fan itself looked okay until we closely examined the male plug on the power cord. The large blade on the plug where it exited the molded portion was arced and shorted. Heat and scorch marks clearly indicated that a short circuit had occurred at this point.
We then took a closer look at the power extension cord for the air-conditioner. We found arcing on the metal horseshoe connector to the ground wire connecting to the molded male plug. Further investigation of the outlet that the plug strip was plugged into revealed that it was wired improperly and had reversed polarity–that is, the incoming electrical wire supplying power to the receptacle was connected such that hot and neutral wires were on the wrong terminals. Tbis caused the large blade on the fan plug to become the hot prong and the narrow (normally hot) prong to become the neutral prong. We had found our ignition source.
When the daughter pulled the multiplug power strip across the floor, the ground wire on the air-conditioner extension cord contacted the large (and now hot) prong of the room fan, which was plugged into the power strip. The fan plug was not fully inserted into the receptacle on the power strip, allowing this to occur. This energized the outside case of the air-conditioner, which in turn energized the aluminum storm window and aluminum siding on the house. An arc was struck between two pieces of siding on the corner of the house. This was sufficient to cause the ignition of the fiber backerboard under the aluminum siding.
WHY MAKE THE EXTRA EFFORT?
Some might ask why we put such time and effort into investigating a fire that was accidental and not of great magnitude or monetary loss. First, we are fortunate to have the time and resources to investigate every fire thoroughly. Some jurisdictions have budget and manpower constraints that prevent this type of investigation of every fire. However, such investigations give investigators the hands-on experience they need to sharpen their skills. This hands-on training, coupled with attendance at seminars to learn the latest fire investigation techniques and technology, will result in the most effective investigators/investigations.
There are other reasons to conduct a thorough investigation of every fire. One is to prevent a recurrence of the fire. You can determine if any household appliances were involved; if so, you can get the word out to state and federal agencies that there may be potential problems with those appliances. Such information can be compiled to determine trends and develop plans for corrective action. Finally, if your origin and cause determination is that a fire is incendiary, it is absolutely necessary to eliminate every other possible cause. This can be done only through a complete investigation and combining what you learn through investigation with classroom and seminar training and other professional sources. 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 24-year veteran of the Hasbrouck Heights (NJ) Fire Department.
