G'day Rod,

I dont believe they do, there's nothing listed anywhere on the cylinder or packaging that indicates a Rim Vent Release valve.

G'day Mo, 

Got the following info from recyclingnearyou.com.au :
"Butane aerosol cans or canisters such as those used for camping should NOT be put in the kerbside recycling they are highly flammable if any gas is remaining in them. It's best practice to keep them out of the kerbside bin and dispose of them at your local household chemical drop-off service"

You can you that website to find the drop off location closest to you!

G'day David,

I've just checked for you, and they are 60% butane, 36% isobutane and 2% propane.