Certified Fire Investigator Practice Exam

What does "detonation" refer to in combustion?

1. Propagating combustion slower than sound

2. A minimal combustion process

3. Propagation of a combustion zone faster than sound

4. A controlled burn in a designated area

The correct answer is: Propagation of a combustion zone faster than sound

Detonation refers to a specific type of combustion that occurs when the pressure wave generated by the reaction moves faster than the speed of sound in the unreacted medium. This rapid propagation of the combustion front results in a highly explosive and energetic reaction, which can produce a significant shockwave. In contrast, the other options address different aspects of combustion. For instance, the propagation of combustion slower than sound characterizes deflagration, which is a less violent and slower reaction compared to detonation. A minimal combustion process typically does not encompass the characteristics associated with detonative reactions, and a controlled burn in a designated area refers to intentional fire management practices rather than the rapid, uncontrolled energy release associated with detonation. Thus, the characterization of detonation aligns specifically with the propagation of a combustion front at supersonic speeds.