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Reflections on the Cause and Origin

by
Dr. Bernard Béland

Beland, Bernard. Reflections on the Cause and Origin.
Fire and Arson Investigator. Vol 48, No. 1 (September 1997). p 8-9.

In the fire investigation process, it is generally agreed that one first determines the point of origin and then, the cause. While the rule generally applies, it suffers numerous exceptions as will be seen by examples to be discussed. The most important result is that of finding the cause. Finding the area of origin is just one of the steps that helps establishing the cause. Sometimes, the point of origin could be found with some accuracy but still the cause is unknown because there are too many possibilities to consider with no means to eliminate all of them but one. In other instances, the cause of a fire could be known with a high degree of certainty, even though the point of origin is not known. Examples will be given of such cases.

CAUSE-ORIGIN

The semantic problem of using "cause and origin" or "origin and cause" should not bother us in this article. The point of origin­or at least the area of origin­is often found with a reasonable degree of accuracy, assuming the damages are not too extensive. Alternatively, there are numerous instances for which the point of origin is not clear, even in the case of a limited fire that extends only to one room.

If one can determine both the point of origin and the cause from independent facts and reasoning, then one has a very high probability of being right. For example, if the probability of being right is 90 percent in each determination, then the cause is known with a 99 percent certainty. However, this is very seldom the case, since the two processes are often interrelated. In fact, in numerous cases, one finds the area of origin. In that area, a beaded wire is found. Then an electrical arc is pointed as the cause of the fire. This process is wrong since an arc is a normal consequence of almost all fires. The two events are dependent. For example, a fire could be set with a match and paper in the vicinity of an electrical cord and a bead is most likely to be produced. In such a case, the evidence of the arc is almost useless by itself. It is just like the presence of charred wood. It is evidence of the fire and not of the cause. However, if through an independent process, it could be shown that the cord was severely overloaded to the point of constituting a danger of fire in the presence of proper combustibles, then the possibility of an electrical fire becomes acceptable. An overload just above the ampacity of the National Electrical Code (NEC®)would not be sufficient evidence. For example, 20A in a No. 14 AWG copper cable would not be sufficient evidence. The load would have to be of the order of 50A and sustained over a long time. The exact conditions would have to be evaluated for each circumstance such as ambient temperature, thermal insulation and other factors.

All too often, the fire investigator determines the general area of origin, then finds evidence of beading and concludes as to the cause. The report then mentions that the exact point of origin was determined and, at that point, only electricity could have caused the fire. Often the point of origin was not clear by determined, and the report is silent on the exact nature of the electrical fault and on the reason for the fault to have happened so as to cause the fire. The electrical cause was used as an example, but other causes could have been used to illustrate the point.

FIELD CASES

A few field cases will now be discussed briefly to illustrate the introductory remarks. They correspond to actual cases that have been investigated, although there could be some modifications to better illustrate the discussion. Most of them would have been encountered by fire investigators, although the details could vary.

CASE I (FLOATING NEUTRAL)

A truck ran into a triplex cable that fed a summer house and severed the neutral. The house had no public water system and, therefore, the ground was provided only by electrode rods driven into the soil. Severing the neutral removes the house from the power company ground. The open neutral constitutes a serious danger of fire, that is enhanced by the poor ground. A fire ensued about half an hour later and completely destroyed the house. Under that open neutral condition, some of the loads in the house are fed by a higher than normal voltage while others are underfed. The actual values depends on many circumstances; typical values could be 150 and 90V or some other combination which sum equals 240V.

In such a case, the cause of the fire is known with a reasonable degree of certainty. It is the floating neutral. This is the most probable cause by a large margin. Other causes could be considered as a remote possibility, but should be rejected unless other strong evidences are found. This is a good example of a fire in which the point of origin is unknown but the likely cause is very clear.

Other engineers working for the truck insurance company dug the debris, found evidence of beaded wires and claimed that the fire was caused by electrical malfunction that had nothing to do with the severance of the neutral. This is not exceptional and is often encountered in practice. There is a tendency to write a report that pleases the organization that retained the service. A fire is a very uncommon phenomenon. In a given house, it does not happen for years. If a fire happens almost simultaneously with the creation of a dangerous situation, then, there is probably a relationship between the process and the fire. That relationship can sometimes be removed but very strong evidences must be presented to remove it.

CASE 2 (THAWING OF WATER PIPES)

On a very cold afternoon (-35°F), an oil-fired furnace broke down. An electrician was called to install temporary electrical heating to prevent the water from freezing and protect the facility. The installation was completed around 10 p.m. and a fire was discovered some three hours later. The fire completely destroyed the building. This author was called to investigate the fire and, if possible, find evidence to recover the losses from the electrician.

The investigation revealed that the electrical work was well done. He had used the proper size of conductors and the work was professional, at least for a temporary work that was to be removed the next day after a new furnace installation. The code was not adhered to in all details. For example, cables to the heaters were run on the concrete floor without mechanical protection. Although the code was not adhered too, that specific violation constitutes no danger of fire and, it will be hard to blame the electrician.

An investigation did not reveal the area of origin. There were numerous low burns everywhere. There was also numerous evidence of arcing in the temporary wiring and elsewhere. This is not unusual. The close time proximity between the electrical work and the fire suggests a relationship between the two events. But there was nothing wrong with the installation. Further investigation revealed the presence of an oxyacetylene torch with its tanks. That facility was used to prepare and store food. Acetylene is not used to prepare food and, therefore, its presence was intriguing and called for an explanation. The owner was questioned. He also owned a garage. That is a good reason to own that welding equipment. The next question was 'Why did you have that equipment at the food plant?" With great embarrassment, he explained that, to prevent the freezing of the water pipes, while the temporary heating was being installed, he used the torch to heat the pipes. The pipes were installed close to the walls that were finished with loose-fiber insulating board.

That material may be ignited by a match in a matter of a few seconds. If one blows out the flames, the material will sustain smoldering combustion inside. The inside is red hot while the outside surface is black and charred. That smoldering process proceeds at a speed of inches per hour and could eventually lead to a flaming fire. The owner was told that the thawing process is dangerous under the circumstances. He agreed and replied that, in fact, he started fires on the wall a few times. But he was with his son. His son had a bucket of water and quenched the flaming combustion a few times. Tests showed that, under that condition, although the flames are extinguished, smoldering combustion could continue inside.

Very clearly this fire was most probably caused by torch-thawing of water pipes. The cause is known with a very reasonable degree of certainty while the point of origin is unknown.

REMARKS

These two examples show clearly that, sometimes, the cause could be known reasonable with a reasonable degree of certainty, even if the point of origin is unknown. Numerous other examples could have been used.

The second example requires further comments. The owner of the building who conducted the thawing process already knew­or, at least, strongly suspected­the cause of the fire. In fact, he tried to hide the fact. When he was asked if he had done anything dangerous that could have caused the fire, he said no. However, when he became aware that the torch had been found, he was clearly ill at ease. Obviously, the fire was not intentional. The fire resulted from a dangerous process that was not conducted properly.

Numerous other examples of such fires could be discussed in which there is already someone who suspects the cause because of some processes that were performed. The perpetrator of the process will do everything he can to avoid being pointed as responsible. It is human nature to be reluctant to admit one's fault. The culprit is often determined by carefully investigating the fire scene, looking for something unusual or out of place that calls for some explanation. Often, the fire investigator does not even know specifically what he is looking for. By being inquisitive, one sometimes may solve a complex problem. In fact, the solution often looks very simple, once found. Complex explanations for fire cause are often faulty. This author knows of many fire cases in which there was already someone that knew­or at least suspected­the cause of the fire. The above case is just one example.

The first case stresses the relation that often exists between a fire and a dangerous act or process that happens in close time proximity with the fire. The second example stresses the same point, but adds a word of caution. That relation may not be unique. When something happens such as the failure of the furnace, not only the electrician's work could have caused the fire but other acts or processes could also have taken place.

CONCLUSION

It has often been stressed that one must determine the point of origin of a fire before the cause could be established While that sequence is desirable, it suffers many exceptions. Field cases were used to illustrate that it is sometimes reasonable to establish a cause with a reasonable degree of certainty, even if the point of origin is unknown.

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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