Natural gas is lighter than air. If natural gas escapes into the atmosphere, it dissipates rapidly whereas a heavier-than-air gas, such as propane or gasoline, would settle and accumulate near the ground.
Natural gas is colorless. When mixed with the proper amount of air and ignited, invisible natural gas burns with a clean, blue flame. It is one of the cleanest burning fuels, producing primarily heat, carbon dioxide and water vapor.
Natural gas is odorless. When taken from the ground, natural gas is odorless. A harmless but pungent odor is added as a safety precaution. The odorant is so powerful you can smell even the smallest quantity of gas in the event of a leak.