Vapor density greater than one will tend to collect in low-lying areas.

• A. True
• B. False
• C. Not applicable
• D. Somewhat

Answer: (A)

Vapor density describes how heavy a vapor is compared with air. If a vapor is heavier than air (vapor density > 1), it will tend to stay close to the ground, flow into low spots, and pool in depressions, basements, sumps, or near drains. This is why heavier-than-air hazards pose a ground-level risk and require attention to where vapors could accumulate and how to ventilate. In contrast, vapors lighter than air rise toward the ceiling. While airflow can modify this behavior, the default tendency for substances with vapor density over 1 is to collect in low-lying areas, so the statement is correct.