What property is associated with compressed natural gas (CNG)?

Compressed natural gas (CNG) is primarily composed of methane, which is lighter than air. This property is particularly important in safety and emergency response situations. Being lighter than air means that in the event of a leak, CNG will rise and dissipate quickly into the atmosphere, reducing the risk of a fire or explosion at ground level.

This characteristic also impacts how firefighters and emergency responders approach incidents involving CNG. Firefighters need to be aware that if CNG is released, they should monitor the area above the leak for potential concentrations of gas. The lighter-than-air property significantly influences ventilation strategies and the placement of equipment during firefighting operations.

While CNG is indeed odorless and colorless under pure conditions (making it difficult to detect without an odorant added), the defining property when considering the behavior of the gas in the atmosphere is that it is lighter than air. The other choices, which imply that CNG has either high density, is heavier than air, or is odorless and colorless, do not capture as critical a characteristic when assessing its behavior in a leak situation.