Natural gas gives even less power than propane for the equivalent volume but there is so much of it around. It once was burnt off as waste cause before pipe distribution systems it wasn’t worth the trouble to transport. A tank for compressed natural ...
Propane will always be prohibited in low-lying tunnels & strictly prohibited in under ground garages. It is restricted because propane does not dissipate it tends to collect & pool in the low spots. When it comes to explosive gas they err on the side...