Navy refrigerant vapors are how much heavier than air?

• A. 2 to 3 times heavier
• B. Lighter than air
• C. The same as air
• D. 4 to 5 times heavier

Answer: (D)

The main idea here is vapor density relative to air. Refrigerant vapors used on Navy ships have a high molecular weight, so their vapor density is several times that of air. When such a vapor is released, it tends to stay low and pool in the bottom parts of a space—bilges, compartments, and decks near the floor—rather than mixing evenly and rising to reach the breathing zone. That’s why safe response emphasizes ventilating from the lowest points and using detectors in lower areas, because the gas can quietly accumulate where people are closest to the floor. In this context, a vapor being four to five times heavier than air means it will settle out of the air and linger in those lower spaces, creating inhalation and, in some cases, ignition hazards if the vapor is flammable.