In reply to litour: have used one up to about 3500m(alps summer) usual cold problems, keep canister warm and off cold ground, i use a bit of old foam mat, piezo dont always work well when cold, so carry a lighter, as to how it worked fine, no serious problems, but i did note that you can turn it on too much and it blows itself out with a new canister, the advantage to that was it still works until the canister is basically empty, the valve appears to open alot, so you dont need to turn it on much.