Certified Fire Investigator Practice Exam

What is the definition of "deflagration"?

1. The rapid burning of a fuel without a sound

2. Propagation of a combustion zone slower than sound

3. Combustion that occurs in a vacuum

4. A method of fire suppression

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

Deflagration is defined as the propagation of a combustion zone slower than the speed of sound in the surrounding medium. This type of combustion typically occurs with a subsonic pressure wave and is characterized by the rapid but controlled burning of a fuel-air mixture. Deflagration involves a relatively low rate of energy release compared to detonation, where the combustion wave travels faster than sound. In deflagration, the flames spread through the unburned material, causing a gradual increase in temperature and pressure. This process is commonly observed in everyday combustion scenarios, such as in cooking or in certain types of engine explosions, where the reaction does not create a shock wave. Understanding this definition is essential in fire investigation and safety, as it influences the approach taken in managing combustion processes and evaluating fire dynamics. The other options describe different phenomena not aligned with the characteristics of deflagration.