The biggest trouble with fire release and any electronical devices is that fire can be extinguished and power can fail. I think the best methods depend on mechanisms that depend on something that naturally fails eventually and can be sped up. So my favorite idea is still a magnet that holds a key and releases it when an electronic timer cuts off power - or if a fuse blows or if the power supplier has trouble. This will automatically release as predicted when the power stays fine, and immediately, if the power fails. Well, this is still not perfectly safe, if the power line gets hit by a lightning, the electronic device can be destroyed but the power stays on, magnet still works. Now, how likely is that with proper fusing of the power lines?
The wild device I described earlier (rod in a pipe expanded until it cools down) had the same basic idea - the "driving power" of the device should keep it locked and counting, failure of it should release instantly.
Except for the risk, that candles could ignite anything around them, I still like the idea of candle release. New idea: A ballon in a tube, heated. On overheating it burns, on underheating it deflates, both lead to freedom - and quite predictably (unless you put the device onto a radiator).
The wild device I described earlier (rod in a pipe expanded until it cools down) had the same basic idea - the "driving power" of the device should keep it locked and counting, failure of it should release instantly.
Except for the risk, that candles could ignite anything around them, I still like the idea of candle release. New idea: A ballon in a tube, heated. On overheating it burns, on underheating it deflates, both lead to freedom - and quite predictably (unless you put the device onto a radiator).
