Fire/Arson Investigations : Fire/Arson Investigations
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Re: Fire Chemistry Module
Posted by: J L Mazerat (IP Logged)
Date: November 11, 2017 06:16PM
I just took the module and found it to be basic. We do need some basic information for newer investigators. Can there be more advance, without a doubt.
As to the ignition of the gasoline vapors, there is some question. As it was being depicted in the video it is correct. The problem is it can give the wrong perception. It would indicate at no time can gasoline vapors be ignited by a cigarette. It does not address all methods possible for the vapors to be introduced to the cigarette. True science states one cannot prove it is impossible for an event to take place. All that can be said is that under the precise condition that were in place at the time of the experiment ignition did not take place. One only needs to read ASTM 582, Standard Test Method for Minimum Ignition Energy and Quenching Distance in Gaseous Mixtures. “For mixtures composition approaching the limits of flammability, the minimum ignition energy varies so rapidly with the mixture composition that the predictability of the test mixture becomes the limiting and controlling parameter (it is possible that a 0.1% variation in fuel concentration could change the ignition energies by factors of 100 to 1000).
If this is correct the simple explanation in the module could be misleading to newer investigators.
Jim Mazerat
Forensic Investigations Group
As to the ignition of the gasoline vapors, there is some question. As it was being depicted in the video it is correct. The problem is it can give the wrong perception. It would indicate at no time can gasoline vapors be ignited by a cigarette. It does not address all methods possible for the vapors to be introduced to the cigarette. True science states one cannot prove it is impossible for an event to take place. All that can be said is that under the precise condition that were in place at the time of the experiment ignition did not take place. One only needs to read ASTM 582, Standard Test Method for Minimum Ignition Energy and Quenching Distance in Gaseous Mixtures. “For mixtures composition approaching the limits of flammability, the minimum ignition energy varies so rapidly with the mixture composition that the predictability of the test mixture becomes the limiting and controlling parameter (it is possible that a 0.1% variation in fuel concentration could change the ignition energies by factors of 100 to 1000).
If this is correct the simple explanation in the module could be misleading to newer investigators.
Jim Mazerat
Forensic Investigations Group
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