1. Collecting and analyzing evidence
Fire and explosions:
Collecting and analyzing evidence

2. The Fire Scene FIRE INVESTIGATION
Normally, a fire has a tendency to move in an upward direction, and thus the probable origin will most likely be the lowest point showing the most intense characteristics of burning.
At the suspect point of origin of a fire, ash and soot, along with all porous materials which may contain excess accelerant, should be collected and stored in airtight containers, leaving an airspace to remove samples.
If an accelerant is used, some unburned quantity will always remain at the fire scene.
FIRE INVESTIGATION

3. The bombing scene EXPLOSIONS
Most high explosives will leave a crater, which helps locate the origin of the explosion.
Low explosives also can leave a crater if they are confined in a container such as a pipe. This allows the pressure of expanding gases to build up.
The entire bomb site must be systematically searched with great care given to recovering any trace of a detonating mechanism or any other item foreign to the explosion site.
Objects located at or near the origin of the explosion must be collected for laboratory examination.
EXPLOSIONS

4. The bombing scene EXPLOSIONS
Some undetonated explosive always remains at the scene.
As with fire evidence, bombing evidence should be stored in airtight containers.
Plastic containers are not suitable for fire or explosion evidence, because accelerants and explosives contain hydrocarbons, which react with plastic and can diffuse through them.
EXPLOSIONS

5. Back at the Lab EXPLOSIONS
Typically, in the laboratory, debris collected at explosion scenes will be examined microscopically for unconsumed explosive particles.
Recovered debris may also be thoroughly rinsed with organic solvents such as acetone and analyzed.
EXPLOSIONS