Fuel & air explosion investigations: The challenges - Part 2
A significant factor relating to scene access following a fuel and air explosion is the structural condition of the building where the explosion occurred.
Part 1 of this two-part series examined several different scenarios for fuel and air explosion investigations.
One of the most significant factors relating to scene access following a fuel and air explosion is the structural condition of the building where the explosion occurred. Depending on the size, dispersed explosions will create pressure effects that tend to push or heave a surface or object rather than the typical shattering effect that will often occur from a concentrated chemical explosion. The structure, such as a silo, manufacturing plant or domestic property will therefore often have severely compromised walls, roofs and foundations due to a fuel or air explosion.
This may mean that there is limited safe access possible, and in some cases, no access until the structure is demolished. Investigating a fuel and air explosion is often challenging, even with a “preserved” scene, so any subsequent demolitions only make that undertaking more difficult.
The insurance industry professional will have several questions to ask the forensic investigator to answer. The two main questions are discussed here along with why investigators cannot always give definitive answers.
What caused the explosion?
In contrast to a concentrated explosion such as the functioning of an improvised explosive device (IED), or a mechanical blast such as a boiling liquid expanding vapor explosion (BLEVE), a fuel or air explosion will often not have a clearly defined “seat” or origin. Depending on its size and location, an IED will often leave a defined cavity after it has functioned. A burst pressure vessel will be evident.
However, the area of greatest damage following a fuel and air explosion will not necessarily be at the site where the blast originated. The most significant damage to the structure may be some distance from where the ignition source and fuel and air mixture met. This may be due to how the explosion pressure wave vented from the structure, the degree of building collapse, areas of greater fuel load, and whether a fire resulted from the initial explosion.
For the investigator to be able to tell the client what caused the explosion, they need to establish what the fuel and air mixture was (i.e., a propane leak), what the ignition source was (i.e., a spark) and how the two came together. The investigator can establish this from a combination of witness statements, CCTV footage, the nature of the work being carried out in an industrial setting, the presence of available fuels that can form an explosive atmosphere in the air, and an inspection of the remaining physical evidence.
Depending on the size and nature of the explosion, as well as the availability of access to witnesses and evidence, it may sometimes be the case that the fuel is determined, but the ignition source can only be narrowed down to several possibilities.
Who is to blame for the explosion?
This is a crucial question for the insurance industry professional or lawyer who wants to know if there is a potential for repudiation of an insurance claim, subrogation, or issues with liability and potential lawsuits.
To answer this question, the forensic investigator will need to consider the totality of the physical and testimonial evidence, as well as all available pertinent documents. These documents may include the insurance policy, property history, any maintenance or repair reports, blueprints, standard operating procedures (for an industrial or commercial incident), any fire and explosion risk assessments, and compliance with relevant local or federal regulations concerning hazardous explosive environments.
The goal for the forensic investigator is to provide a clear answer to this question, both in verbal conversations with the client and in the formal report. If a definitive answer isn’t possible, it’s usually because crucial information relating to the property and activities of the occupants before the explosion are obscured – either deliberately or by accident.
The investigation of a fuel and air explosion is a complicated and often complex process. The forensic investigator can ease the client’s job by providing clear, unambiguous answers to questions, communicating often, explaining limitations to the findings, and being proactive in obtaining access to evidence and witnesses.
The manager of Jensen Hughes’s Warrington, U.K. office, Gareth Williams is a senior investigator with experience in fire and explosion investigations in many different settings. Throughout his career, he has investigated over 500 fires in the U.K., Europe, Australia, the Pacific and Southeast Asia. Contact him at gareth.williams@jensenhughes.com.
Related: