Fire Triangle
Arson investigations may be particularly challenging, because evidence is likely to have been destroyed in the fire or contaminated during firefighting operations. It normally takes longer to investigate than an episode of TV programme Crime Scene Investigator CSI might suggest because there can be literally tons of debris to sift through in search of chemicals that may have been used as a so-called accelerant. Traces of these can remain detectable even after a major conflagration. Highly-trained sniffer dogs are a traditional resource but these animals may not be available when needed or have insufficient, unsafe access. Many accelerants are hydrocarbon-based fuels such as gasoline (petroleum), diesel fuel, kerosene, turpentine, butane, and various other flammable solvents collectively known as volatile organic compounds (VOCs).

But despite the fact that fire is a common, everyday phenomenon, it is a very complex chemical, physical, and thermal event. Investigative work will focus on the ‘fire triangle’ of oxygen, fuel, and source of heat or ignition, and in cases of arson at least one of these will have been tampered with.

Pros Of Using PIDs

One such tool for the detection of accelerants at fire scenes recommended by investigators is the photoionisation detector (PID) which has already proven to be an ideal solution for the detection of relatively low level VOCs for health & safety and environmental applications. These devices are battery powered and portable and can be deployed rapidly and safely to test areas between floorboards and under carpets where residual traces of accelerant may remain.
– Crime Scene Investigator Network

• PIDs are portable and battery powered making them ideal for field applications.
• PIDs are a quick, simple to use and accurate method for the detection of accelerants at a fire scene.
• PIDs are very sensitive to commonly found accelerants and will detect hundreds of gasses and vapours.