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Apparent Electrical Fires

by Bernard Béland

Béland, Bernard. Apparent Electrical Fires.
Fire and Arson Investigator. Vol. 47. No. 2 (December 1996). p 19-21.

INTRODUCTION

A fire is a complex phenomenon even if it involves only a match or a candle. A fire in a building is a real challenge and its investigation is full of pitfalls. It is easy to err concerning the point of origin, and even more so in relation to the cause. The problem is usually not of finding "a cause" (there are normally numerous possibilities) but finding "the cause" to the exclusion of all others. Pointing electricity as a cause is usually quite easy and often wrong since electrical wires and devices are almost everywhere in any building. These devices will obviously be damaged by the fire. Numerous authors have challenged these electrical fires (1-4). Often electricity is pointed without any evidence except for its mere presence in the area of origin of the fire. That mere presence is an extremely weak evidence since it is almost always so. Most of the fire investigators are aware of cases in which electricity was pointed as the cause to find later that arson had been committed, that dangerous processes took place, such as welding, just before the fire or even that electricity was not connected in the suspected circuit.

In this article a few field cases will be considered in which electricity was pointed as the cause without any evidence. In these cases, legal actions were taken against the manufacturer, the electrician or other persons who had something to do with the electrical installation. In one case, extreme hardship was suffered by the electrical contractor. It is realized that these cases may not be typical of most fire investigations. Still, such cases are quite numerous. Such cases were encountered in numerous situations by this author.

STICKING CONTACT IN A BREAKER

During an evening, a teenager was cleaning bicycle parts with gasoline in a garage attached to a house. A fire was ignited accidentally, and was extinguished in a matter of a few minutes. Later, during the night, a fire started in the garage and eventually destroyed the garage and damaged the house to render it a complete loss. In the absence of any specific evidence, it would seem that the most probable cause of the second fire is a rekindle of the first fire that had not been properly extinguished.

A fire investigator found an arced 8/3 copper cable that fed an electric range. He checked the 40-A breaker that protected that circuit and found it in the tripped position. He then checked the breaker with an ohmeter with a buzzer and found that it had not opened. He then concluded that the breaker contacts had welded and eventually the breaker manufacturer was sued. He unhooked the breaker, put it on his car seat and brought it home. From that point, everyone that tested the breaker found the breaker contacts open, both electrically and physically. It was claimed that the car vibrations had broken the contacts loose.

The fire investigator was the only one that ever detected the closed contacts, the surface of which were normal. He probably misused the meter and did not properly interpret the reading. The instrument was easy to misuse and the fire investigator was not competent enough in electricity to properly use the instrument. An even more likely explanation is that the measurement was made while the breaker was still connected in the panel. In such a case, more likely than not, a measurement will show a low resistance even if the breaker is in the open position. This is due to the numerous other connected circuits and short-circuits in a burned house. To properly check the breaker for shorted contacts it has to be disconnected from the electrical circuit.

The theory of the fire investigator is that a short circuit was developed in the 8/3 cable and the breaker failed to open. The cable then became very hot and started the fire. There are many faults with that argument. The cable, where it was not damaged by the heat of the fire had no sign of overheating even between the arced spot and the breaker panel. Furthermore, that breaker panel was protected by a 60-A main breaker. In the event of a failed 40-A breaker, the circuit was still protected by the 60-A breaker. Assuming a properly functioning 60-A breaker, any short-circuit current would produce a temperature rise of the cable by about 5 to 10°C under the worse conditions. An even worse situation would be an overload of about 75-A Under that condition, the breaker could take a long time to open. Assuming it does not open, the temperature rise of the cable would then be 40°C above ambient. The fire investigator never considered that 60-A breaker as a further protection.

Notwithstanding all these weaknesses of the case, the fire was supposedly of electrical origin and the breaker manufacturer was sued.

FIRE IN WOOD SHAVINGS

In a storage building, a fire was discovered in the attic space around a recessed lighting fixture. The fire was extinguished quickly and the maximum depth of char on wooden studs was about a quarter inch deep. The attic space was insulated with wood shavings to a depth of over one foot. That insulation was heavily charred and many fire debris were spread away some distance from the point of origin. Some ten hours later, the fire rekindled around the same area but was not controlled until the building was a complete loss.

After the first fire, an electrician was called. He disconnected the circuits that had been damaged by the fire or water and installed some new cables. On the evidence of beadings, an engineer pointed these electrical repairs as the cause of the fire and the electrician was sued.

It should be quite obvious that the most probable cause of the fire is a rekindle of the first fire that was not completely extinguished. The electrical cause is just a remote possibility for which the evidence is weak or non existent. It must be admitted as a possibility in the sense that almost anything is possible. Again a remote possibility was pointed as the cause, while a more obvious cause was rejected or neglected. Beading is no evidence of the cause; it occurs at numerous places in almost all fire, including the area of origin. The evidence of beading would be very useful if it was unique and that only one particular meaning could be attributed to it. But, this is not so.

ARCED AND BEADED CABLE

In a tavern, there was a long and large corridor that lead to the washrooms. The ceiling was covered by cellulosic acoustic tiles and had combustible thermal insulation such as cardboard sheeting. Such a material can be ignited by a match in about one second. The ceiling in the corridor had an opening to give access to the attic space with the use of a ladder if necessary.

At the time of the fire, the building was under extensive renovation, including work in the attic space. During the day, the tavern was closed so that work could be done more easily and would open during the evenings for the patrons. The day of the fire, numerous workers went up in to attic for work on electricity, plumbing, refrigeration and numerous other reasons. Power tools and propane torches had been used. There was temporary electrical wiring including 300-W lamps with extension cords and, of course, the regular wiring. There were also recessed lighting fixtures.

At the time of the fire, during the evening, there was no one in the attic but the trap door above the corridor was left open. Numerous patrons of the tavern were on the premises. One of the clients noticed a glow from the attic space above the open trap door. The fire was reported but the building was eventually destroyed to the ground.

A fire investigator found a melted copper wire with beading. That was pointed as evidence of the cause. The electrician was sued causing great hardship to his business. The investigator concluded that he had eliminated all causes but that of the beaded wire and, without a doubt, that was the cause.

As usual, there were numerous evidences of beadings in many other cables. None of these could be eliminated as a possible cause. The one that was retained was handy since it was one that was installed as temporary wiring a few days before the fire. The destruction was so advanced that there was no clear evidence as to the point of origin. In fact, most of the attic space was a possible point of origin. The glow from the attic was seen at the point of the open trap door, but that does not suggest the point of origin. The origin could have been anywhere and the glow would always be seen at that opening, particularly in a poorly lit area.

Obviously, in that fire, besides arcing, there were numerous other possibilities. Among the most obvious one would be the actions of one of the workers during the day such as smoking materials and soldering of copper pipes. A thermally insulated recessed lighting fixture, one of the extension cords or a light bulb are other possibilities. Not to be neglected is that a patron could have thrown a lit cigarette in the attic. In this particular instance, the judge retained that temporary wiring as the most probable cause.

A GARAGE DOOR OPENER

A man drove his car back home into the garage using the automatic garage door opener for both opening and closing the garage door. He then went to the house. A fire in the garage was discovered about 40 minutes later. The roof of the garage was completely destroyed and the walls were also burned completely except for the first foot or so close to the ground. The char pattern on the remaining of the walls was almost uniform over the whole perimeter of the garage. Similarly, the car was destroyed to leave only distorted steel. When the fire was discovered, the detached garage was fully involved.

From the above evidence a fire investigator concluded that the fire started in the center of the garage because of the uniform char pattern. That would seem to be a weak argument since one has always a uniform char pattern when almost everything is burned. Since the lower parts of the wall were not completely burned, he further concluded that this was a "high fire" and it must have started at the ceiling level. Again, that evidence is very weak since most fires that last for some time do more damages at the higher levels than at the floor level. This is so even if the fire starts on the floor. The garage had a concrete slab on ground.

In his report, the fire investigator, using the above arguments, concluded that the only possible cause for the fire was an electrical malfunction of the garage door opener. He was prudent enough however not to be specific on the failing process or the part that failed. The manufacturer of the garage door opener was sued. In his report, the fire investigator neglected to address many points such as that of the motor that was thermally protected. Had the motor been stalled for any reason, a fuse would have blown quickly and the thermal protection would have opened.

There was no obvious causes for this fire although there were quite a few possibilities besides the door opener such as the lights on the ceiling and the electrical wiring in the garage. The car could also have started the fire for numerous reasons. Furthermore, the driver was a heavy smoker; a dropped cigarette is then a further possibility. In this case, with the evidence available one should have refrained from giving a probable cause since all causes were about equally probable although, the most likely cause is smoking materials. The driver denied that he had smoked; however, a passenger that was dropped off about one minute before the car was parked in the garage was sure that the driver was smoking at the time of the drop off.

A HEAT TAPE FIRE

In a crawl space underneath a house, a fire was ignited and eventually went up into the house through holes made to pass pipes. A heat tape installed on a water pipe was damaged for a length of a few feet. The resistive wires were severed. The point of origin was not very clear but part of the tape was in that area. It was concluded that a faulty heat tape arced and caused that fire. The remains of the tape was tested. It was found to be open- circuited at two points where connections are made. Obviously the tape could not provide any heat even if it had been connected and the thermostat had been on. At the time of the fire, the ambient temperature was high enough so that the properly operating thermostat had to be in the off position.

This make up three open-circuits in series. It would seem to be extremely unlikely that all three had been on before the fire and were off after the fire. These three open-circuits had never been in the fire area. They had only been subjected to water from the fire-fighting.

DISCUSSION

A few filed cases of fires have been discussed in which electricity had been pointed as the cause. In all instances, the evidence was very weak or nonexistent. In other cases, the electrical cause was a possibility to consider but with further investigation, had to be rejected The mere presence of electrical cables or devices is often used as evidence of the cause. The investigator should resist this easy way out of a case. Electricity is so much used in any building that, in most cases, there are numerous electrical wires in the area of origin. The cables are always damaged such as burned insulation that produces short-circuit and arcing. The mere presence of electrical cable, even with evidence of arcing, should not be used as evidence of the cause. However, under certain circumstances, certain facts could help point to the electrical cause. These facts should be significant. The mere flickering of lights when a motor is started or the use of a 20-A fuse instead of 15-A are not, by themselves, sufficient evidence to point to electricity.

In a typical house, there is about one foot of cable per square foot of floor area and, sometimes, much more. Over hundred feet of flexible cord is quite common. The reader may be surprised to learn that a typical house has about 50 electrical motors. Most people think that they have just a few. An air conditioner has compressor and fan motors. A refrigerator has a compressor motor plus, sometimes one two three motors for air circulation and cooling of the heat exchanger. Most furnaces have two motors for the burner and the heat exchanger fluid. Even a microwave oven has a motor for the cooling fan of the klystron.

These cases were selected to show how easy it is to err in pointing a cause for a fire. This is particularly true of fires in which electricity is one of the possibilities. It shows that fire investigation is not easy and numerous errors are often made. Most of them are probably from incompetence and misinformation. It should be stressed that this selection of cases is not necessarily typical of fire investigation. Another set of cases could have been chosen to illustrate just the reversed situation in which very good investigations were made. However, these field cases should not be considered as exceptional. Almost all of these cases were encountered on a few occasions. In some fires, there are many fire investigators. It is not unusual to have as many different assumed causes for a single fire as the number of fire investigators. Even the number of points of origin sometimes approaches the number of experts retained for the case. If there are four causes for a given fire, it would seem logical to assume that at least three causes are wrong. In such a case, the expert most likely to be right is the one who has classified the cause of the fire as unknown.

CONCLUSION

This article has illustrated the difficulty in investigating fires. Numerous pitfalls were discussed. Although these cases were selected to show the poor investigation in some instances, other cases could have been chosen to illustrate the reverse situation.

REFERENCES

1. B.V. Ettling, "Are We Kidding Ourselves?", F&AI, Vol. 34, No. 4, June 1984, pp. 19-22.

2. J.F. McPartland, "AU These Electrical Fire? - Hogwash!, The National Fire and Arson Report, Vol. 2, No. 3, September 1983, pp. 5 and 10.

3. B. Béland, "Examination of Electrical Conductors Following a Fire," Fire Technology, Vol. 16, No. 4, November 1980, pp. 252-258.

4. B. Béland, "Electrical Damages - Cause or Consequence?," Journal of Forensic Sciences, Vol. 29, No. 3, July 1984, pp. 747-761.

About the Author

For the past 30 years, Dr. Béland has studied fires under laboratory conditions and also at fire scenes. Many of the fires, including full size fires in buildings, were started intentionally to study their behavior. Dr. Béland specializes in the study of ignition, thermal transfer and electrical causes. Many systems and devices were used in his experiments to study their outcome and to determine what types of damage could be associated with the causes that resulted in the fire. He has also experimented with numerous systems to determine under which conditions they could constitute a danger.

Dr. Béland's research has resulted in the printing of over 100 technical articles in specialized journals such as: L'Ingenieur, Fire Technology, Journal of Forensic Sciences, Fire & Arson Investigator, Power Apparatus and Systems, Electrical Business, Proceedings of the Institute of Electrical Engineers and others.

Dr. Béland has investigated over 900 fires and electrical failures in which a total of 300 lives have been lost. He is retained by equipment manufacturers, power companies and research centers. Dr. Béland has done consulting work and lecturing in eight Canadian Provinces, 37 states throughout the U.S., four European countries and New Zealand. He has served as an expert witness in approximately 100 cases for numerous jurisdictions.

Dr. Béland has taught at numerous universities in Canada. He recently retired from the Universite de Sherbrooke as a Professor in the Department of Electrical Engineering. Dr. Béland is currently a private consultant in his own firm.

Reprinted with permission.

 
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