"m in same situation, going away with grandkids next week in forest. We sleep in driveaway awning anyway and also have co2 detector in van, are we going to get turned away, already spent too much money on the van this year !!"
I hope you mean a Carbon Monoxide detector. Although CO2 will also finish you off but in a nicer way.
Anyway, that will alert you for combusted gases, but not for leaks - which you might be able to smell if you aren't asleep. To be honest, sleeping in a small confined space with a gas canister a few cm away, probably not a bad idea to have some sort of permanent venting or a window open.