A chemical with a vapor density greater than 1 will tend to

• A. Collect in low areas and below grade places.
• B. Dissipate immediately when exposed to air.
• C. Lift into the air.
• D. Spontaneously combust when exposed to air.

Answer: (A)

When a vapor is heavier than air (density greater than 1), gravity pulls the vapor down and it tends to settle in the lowest available spaces. That means it will pool in low areas, basements, depressions, and below-grade locations where air movement is limited. This pooling can create dangerous concentrations even if the vapor isn’t highly reactive, so responders and handlers must consider locating and ventilating these low spots.

Dissipating immediately isn’t typical for heavier-than-air vapors because they don’t rise away from the source; they stay near the ground where they can’t disperse as quickly. Lifting into the air describes lighter-than-air vapors, not heavier ones. Spontaneous combustion isn’t determined by vapor density alone.