Don't touch those switches

In the case of an LPG (propane) leak, turning switches off can be as bad as turning switches on: if the equipment is already powered and running, turning it off could cause arcing in the switch and possibly ignite the gas. Just leave your switches where they are and vent the area. Unpowered automated equipment would be the exception: if your bilge pump isn't running for example, it isn't drawing power and is not at risk for arcing, so turn it off before the automatic switch engages. Also, gaseous LPG is much more stable than gasoline fumes, so don't panic, just go about doing what needs done.