With a specific gravity of 1.53, propane is heavier than air. Unlike natural gas, which naturally tends to rise, propane tends to sink and may accumulate in trenches, drains and other low-lying areas. Keep this behavior in mind if you are called to an incident that involves a propane pipeline.

Be alert for propane in leak or fire incidents involving gas grills, as propane is the fuel most commonly used in these appliances.