Which hazard is a sudden, intense burning of a cloud of fuel dispersed in air, usually gas or vapor, that can be a mist or dust and is short in duration?

• A. Jet
• B. Flash
• C. Pool
• D. Ignition Source (Heat)

Answer: (D)

The main idea here is identifying a flash fire: a sudden, intense burn that occurs when a cloud of flammable fuel—gas, vapor, mist, or even dust—dispersed in air finds an ignition source. Because the fuel is spread out in the air, the flame front can sweep through quickly and briefly, producing a powerful but short-lived fire. This is different from a jet flame (a continuous flame issuing from a source), a pool fire (fuel burning on a surface), or an ignition source itself (which starts burning but doesn’t describe the dispersed-fuel hazard). So the best description of this hazard is a flash fire.