Yeah, We Do That! (a continuing series)

is By Carol Chavez

This week’s installment of “Yeah, We Do That!” focuses on explosions.  In particular a home explosion that was caught on film in Dallas, TX just before 6 a.m. this past Tuesday.  The home where the explosion occurred was destroyed and neighboring homes had shattered windows, melted blinds and blown down walls.  Luckily there were no fatalities, which is not always the case.

The first responders conducted the initial investigation while on scene.  Their documentation and observations are an important piece of the investigative process for forensic engineers who will be called to the scene once the initial fire has been contained and the site is safe for further inspection.  In addition, interviews and written documentation taken from witnesses are important pieces of the investigation.

In any instance there are several concerned parties who may decide to call on a forensic engineer to understand what happened and protect their interests.  Public utility companies, manufacturers and installers of appliances found at the scene, and the insurer of the property are just a few of those entities.

When the forensic engineer arrives on scene, one of the first things they will do is take photos.  At AEI Corporation the methodology is to start from the outside of the structure in a clockwise direction, making sure each photograph slightly overlaps the last so it is clear how the structure and photos of the scene fit together.  Next, the inside of the home is photographed.  Every room, whether it’s involved in or affected by the incident is included.  Generally, hundreds of photos showing great detail are taken.  Often times, knowing where the origin was NOT is critical to finding the where it IS.  Photography and scene sketches are extremely vital to an investigation.  Once the structure has been torn down and items have been removed, there is no way to get that detail back.

During the investigation the engineer will be looking at gas fueled appliances and the piping and connections feeding those appliances, including outside of the home to the main lines.  The entire scene will be documented in a nondestructive fashion, including the location and condition of those appliances. 

It is likely that the gas system will then be leak tested.  This is accomplished by supplying pressure using a test regulator that gives the engineer information about the pounds per square inch.  If the gas system does not hold the pressure, then the engineer knows there is a leak that needs to be identified.  They will work methodically through the entire system to identify the number of and location of those leaks.

As the leak or leaks are identified, the engineer will consider the conditions in the area of that leak.  For instance, is it obvious that something collapsed on the piping in the area of the leak or that it was damaged during the first responders efforts to control the ensuing fire?  If there is a clear and logical cause for the damage to an area of gas piping, then it may provide enough detail to rule that particular leak out as a cause of the explosion.  The size of the leak will also be considered to determine if it was sufficient to cause the type of gas accumulation inside the subject building that would be necessary to cause the explosion.

In the event it appears a particular appliance was contributory to the explosion, demonstrative testing utilizing an exemplar may be done at the forensic engineer’s laboratory.  The point of that testing is to demonstrate and document the likelihood that the conditions identified at the scene particular to that appliance were or were not sufficient to be the cause of the explosion.

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