Which gas is heavier than air and can accumulate in low areas?

Propane is indeed heavier than air, which means that if it is released into the atmosphere, it will tend to settle in low-lying areas. This property is particularly important for safety considerations in handling and storing propane, as it can create a significant risk of accumulation in wells, basements, or other depressions where ventilation may be limited.

When propane gas escapes, it will not dissipate quickly into the air like lighter gases would; instead, it remains near the ground, potentially leading to dangerous concentrations. This characteristic is one of the reasons why appropriate measures, such as proper storage and ventilation practices, are so crucial when working with propane to prevent hazards such as explosions or suffocation.

In contrast, gases like hydrogen are lighter than air and would rise rather than accumulate in low areas. Other options, while they may also have unique properties, do not match the specific criteria of being heavier than air and are not as relevant in the context of potential accumulation in low regions as propane is.