Certified Fire Investigator Practice Exam

Which statement best defines a low explosive?

1. An explosive that ignites without producing a shock wave

2. An explosive that detonates at supersonic speeds

3. An explosive that detonates at subsonic speeds

4. An explosive that is used for military purposes only

The correct answer is: An explosive that detonates at subsonic speeds

A low explosive is characterized by its ability to produce a relatively slow reaction speed when ignited, typically detonating at subsonic speeds. This definition indicates that the explosive undergoes a combustion process that leads to a rapid expansion of gases, resulting in a pressure wave that propagates slower than the speed of sound. Common examples of low explosives include black powder and smokeless powder, which are frequently used in fireworks, propellants, and some types of blasting applications. The other descriptions do not accurately encompass the nature of low explosives. For instance, the assertion that a low explosive ignites without producing a shock wave misrepresents the nature of low explosives, as they still produce a pressure wave, albeit at a subsonic speed. The classification of an explosive that detonates at supersonic speeds aligns more with high explosives, which are capable of producing a shock wave and a much more forceful reaction than low explosives. Lastly, labeling low explosives as solely for military purposes is misleading since they have extensive applications in civilian contexts, including construction and fireworks, thereby emphasizing their versatility beyond military use.