In reply to kipper12:
Assuming you are talking about the standard primus type cartridges the standard procedure would be to let them fizzle out, then punch holes using a pocket knife or screw driver, wait a couple of days, and put them in any metal recycling bin.
CB
edit: If you want to put gas cyclinders into a fire, use the big acetylene ones used for welding rather than the puny backpacking stove canisters. My school was once evacuated when the building site next door caught fire and they did not get the cylinders out in time, resulting in some spectacular fireworks. The fire department also decided to stay clear. Good thing too, the cylinder that went furthest flew about 2 miles, landing inside the adjacent army base.
Post edited at 14:36