Cooperative Personnel Services Firefighter (CPS) Practice Exam

The Minimum Explosible Concentration (MEC) is defined as the minimum concentration of combustible dust in the air that is capable of propagating a deflagration, which is a type of fast, but not supersonic, combustion process. This concept is crucial in fire prevention and safety, particularly in environments where dust can accumulate and create an explosive atmosphere.

Understanding the MEC helps in setting safety standards and establishing guidelines for managing combustible dust in various industries. Properly controlling the concentration of dust in the air is essential to prevent catastrophic explosions, making this definition vital for fire safety professionals and industrial operators.

The other choices presented do not accurately define MEC. The density of a combustible mixture measures the mass per unit volume but does not indicate the concentration relative to air necessary for an explosion. The pressure at which a deflagration occurs is related to the conditions under which combustion can happen, but it does not define the concentration itself. Similarly, while the concentration threshold for gas mixtures is important, MEC specifically pertains to dust rather than gases. Therefore, option B is the most accurate definition.