A _______ occurs when a flammable liquid is spilled and some portion of the liquid vaporizes as the material comes into vapor-liquid equilibrium with the surrounding atmosphere; then, as the vapor cloud spreads, it encounters a source of ignition.

A _______ occurs when a flammable liquid is spilled and some portion of the liquid vaporizes as the material comes into vapor-liquid equilibrium with the surrounding atmosphere; then, as the vapor cloud spreads, it encounters a source of ignition.

• A. Flash fire
• B. Vapor cloud explosion
• C. Pool fire
• D. Steam ignition

Answer: (C)

Ignition of a flammable vapor cloud formed after a liquid spill. When a flammable liquid is spilled, part of it can vaporize and create a vapour–air mixture in the surrounding atmosphere. If that vapour cloud spreads and encounters an ignition source, the mixture can ignite rapidly, producing a flash of flame that moves through the vapour cloud. This is the scenario described by a flash fire, where the hazard comes from the vapour rather than from burning liquid on a surface. A pool fire involves flames on the surface of the liquid pool itself, not a moving vapour cloud igniting in air. A vapor cloud explosion would require a more energetic, often confined explosion of the vapour cloud, not just a spreading ignition. Steam ignition isn’t relevant here because steam is not a flammable vapour.

Ignition of a flammable vapor cloud formed after a liquid spill. When a flammable liquid is spilled, part of it can vaporize and create a vapour–air mixture in the surrounding atmosphere. If that vapour cloud spreads and encounters an ignition source, the mixture can ignite rapidly, producing a flash of flame that moves through the vapour cloud. This is the scenario described by a flash fire, where the hazard comes from the vapour rather than from burning liquid on a surface. A pool fire involves flames on the surface of the liquid pool itself, not a moving vapour cloud igniting in air. A vapor cloud explosion would require a more energetic, often confined explosion of the vapour cloud, not just a spreading ignition. Steam ignition isn’t relevant here because steam is not a flammable vapour.