Natural Gas has is within explosive range from about 5% to about 15%. If the air is made of of less than 5% of natural gas or more than fifteen percent of natural gas, then it does not really pose a risk as a fire hazard.

Gasoline is within the explosive range from 1.5% - to about 7.5%. It's range is narrowewr, but I think both of these would be considered to be narrow explosive ranges.

One thing that is better about natural gas is that it is lighter than air. Once it is released, if the natural gas is not burned quickly, then it is more likely to dissipate into the upper atmosphere.