Liquefied petroleum gas (propane) is how much heavier than air?

• A. 1.5x heavier than air
• B. Equal to air
• C. 0.5x lighter than air
• D. 2x heavier than air

Answer: (A)

Propane’s behavior in air is defined by its density relative to the surrounding atmosphere. Because propane molecules are heavier than the average molecules that make up air, propane vapor tends to linger near the floor rather than rise. The common training figure used is about 1.5 times heavier than air, which explains why leaks collect in low areas, basements, trenches, or along the ground.

This understanding informs safety actions: expect gas to pool at floor level, so ventilate, shut off the source if possible, keep ignition sources away from the area, and use detection to confirm dispersion. The other options don’t fit because propane is not equal to air, nor lighter than air, and the typical approximation used in practice is around 1.5x heavier rather than 2x.