Well my old back injury came back and bit me over the weekend (nothing I'd done, just a chronic condition for which I'm on painkillers permanently and which flares up worse occasionally for no apparent reason)  -  and I'm off work unfortunately, laid up, so this has given me an opportunity to post this. Our patio doors were fitted by a very efficient and friendly team, who left a couple of offcuts, and as is my wont with these things, I decided to fire test them (yes, I know I videoed it vertically ). This is with a MAPP gas flame, so running at a temperature of 2020c in air. Best I could do was to get it to ignite for a few seconds, smoke then go out. Almost irrelevant when one lives in a timber framed house of course, as we all know wood burns, but interesting nonetheless I think. Yes it puts off smoke, but then with modern smoke detectors, this is no bad thing and the occupants should be long gone before temperatures reach this level or the smoke becomes an issue. Our house has smoke detectors in every room of course, plus passageway upstairs. In fact, for the duration of the build, and before the mains powered detectors are connected up I've even got battery ones in place temporarily for safety. They are so cheap now, its worth the peace of mind.