Because the CNG is under pressure in it’s tank, the tanks are designed to be, virtually bullet proof. It is damn hard to break open a CNG tank. Of course, like in any vehicle, the fuel lines may be ruptured, but, unlike gasoline, which tends to pool under a car and give off highly volitile fumes, natural gas is lighter than air, and, any escaping gas will tend to float UP and dissipate into the atmosphere. Out in the open air, natural gas is very difficult to ignite once it starts to dissipate.

I had to do a lot of research on alternative fuel vehicles for a previous job, and I had yet to find any verifiable information on any injury or death from a collision in a CNG vehicle, that was atributed, in any way, to the fuel type.
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