How Do You Save Money On a Fire Investigation? 
Avoid reaching an erroneous conclusion.

I was recently hired to perform an engineering evaluation where a coffee maker was believed to have been the cause.  This particular model of coffee maker, which was no longer being manufactured, was designed with three safety devicesa thermostat and two thermal cut-offs (TCOs), to prevent it from overheating.

My initial investigation yielded several useful facts. Starting at the outside of the coffee maker, the power switch was melted. This made determining the on/off state impossible. Going inside, I found that even though the thermostat showed signs of fire damage, it still operated properly. Also, both of the coffee maker’s thermal cutoffs had reacted properly to the heat of the fire. There was severe fire damage to several of the kitchen appliances.  Evidence of electrical arcing was found on the power cords to multiple appliances in the area. 

Following the scientific method, I implemented physical testing to prove or disprove the hypothesis that the coffee maker was the cause of the fire. To begin, I acquired a coffee maker of the same make and model.  In the first test, the exemplar coffer maker was emptied and left on for an extended period of time.  The thermostat properly regulated the temperature of the heating coil, preventing the coffee maker from overheating.  For the second test, a hard wire connection was utilized to bypass the thermostat, simulating a failure.  This allowed the exemplar coffee maker to overheat.  The TCOs activated (and turned the coffee maker off) before temperatures were high enough to cause ignition. The TCOs on the subject coffee maker were activated by an exterior fire, not from overheating.  This physical testing proved that the coffee maker could not have caused the fire.

With this information our client was able to avoid a costly lawsuit, which they would not have won.

NFPA 921 and the Scientific Method

Fire analysis and investigation should be performed in accordance with NFPA 921: Guide for Fire and Explosion Investigations.  The Guide utilizes the Scientific Method. The Scientific Method forms a basis for legitimate scientific and engineering processes.  If the testing proves the hypothesis wrong, then the process is repeated a little differently: collect more data, analyze, develop, and test the new hypothesis. The testing process continues until: “all feasible hypotheses have been tested and one is determined to be uniquely consistent with the facts.[i]”  The problems when following the Scientific Method usually occur in the Analysis and Testing the Hypothesis steps.

The data collected is called empirical data because it is “known to be true. [i]” Caution should be used in witnesses’ observations and statements. Persons involved in a fire incident may have reasons to not tell the whole truth, or forget certain details. Some people just don’t observe well. Many innocent insureds believe that they may not be covered if they did something foolish, like leaving hot oil on the stove burner when they walk the dog, or improperly discarding a cigarette. Arsonists will often try to misdirect the investigation, away from the true origin and cause. Unless the observations can be verified or collaborated, they should not be considered empirical data. Many investigations go wrong when the investigator’s conclusions are based on unfounded observations by an involved witness. When the physical evidence differs from the witnesses’ observations, the physical evidence is typically correct.

Analysis of the Data, and Developing a Hypothesis, (Inductive Reasoning) are based on the investigator’s knowledge, training, experience and expertise. In inductive reasoning, a general principle is formed. This is a workable theory, but would be certain only when all possible instances had been examined. Many hypotheses should be considered and should be based solely on the empirical data.  Be wary of investigations which consider only one possible theory.

Testing the Hypothesis (Deductive Reasoning) is the real meat of the investigation. “A hypothesis can be tested either physically by conducting experiments or analytically by applying scientific principles in thought experiments… [i]Physical experiments are better. “Any hypothesis that is incapable of being tested is an invalid hypothesis… If the hypothesis cannot be supported, it should be discarded and alternate hypotheses should be developed and tested. The testing process needs to be continued until all feasible hypotheses have been tested and one is determined to be uniquely consistent with the facts and the principles of science. [i]”  

“A hypothesis can be said to be valid only when rigorous testing has failed to disprove the hypothesis.[i]” Expectation Bias, reaching a premature conclusion without considering all of the relevant data, and Confirmation Bias, seeing the facts differently in an attempt to prove a wrong hypothesis, must be avoided. These can result in a wrong conclusion and the wasting of much time and money.

How can you tell if the fire investigation is using NFPA 921 correctly?

When the Scientific Method is used incorrectly, erroneous conclusions can be made.  When this happens, time and money are wasted.  The fire/explosion scene is a great place to determine if the Scientific Method is being applied correctly. Are there other potential causes which need to be investigated and eliminated? Has the area of origin been properly determined, or has the area been narrowed to erroneously eliminate other possible causes? Is the suspected cause consistent with the facts and provable?  Have the other possible causes been conclusively eliminated? Does the analysis properly use deductive reasoning/physical testing to determine the one true cause?

Using the Scientific Method will result in a strong, provable determination in court. Showing that the other investigator did not apply the Scientific Method properly is a strong defense in court.  At Fay Engineering, we have been using the Scientific Method before NFPA 921 was published. Our engineers make conclusions based on the facts, which can be backed up, demonstrated, and proven in court.

Randolph J. Harris B.S.Ch.E., C.F.E.I., C.V.F.I., C.P.H.

[i] NFPA 921, Chapter 4: Basic Methodology, 2011 edition. 



Engineers Involved: 

Person Reference: 

Randolph J. Harris B.S.Ch.E., C.F.E.I., C.V.F.I.