Flammable liquids produce what, most of which are heavier than air?

• A. Fumes
• B. Vapors
• C. Mists
• D. Gases

Answer: (B)

When a flammable liquid evaporates, it forms vapors—the gaseous form of the liquid. These vapors are what can mix with air and ignite. For many flammable liquids, those vapors are heavier than air, so they tend to collect near the floor, pool in low spots, and spread along surfaces to ignition sources. That tendency to settle low is a key safety consideration, guiding ventilation and ignition-control strategies around flammable liquids. Fumes come from solids, mists are liquid droplets formed by atomization, and gases are already in the gaseous state, not the vapor produced by a liquid. So the correct term for what a flammable liquid produces, with the heavy-than-air tendency, is vapors.