***Candles can be used on the International Space Station in case of emergency — not for light, but for oxygen.
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The OBA (Oxygen Breathing Apparatus) that fire departments (and the Navy) before SCBA operate on a similar principle.
After donning the rig, you had to pull a pin that would ignite a candle that would start the oxygen generation process. The can holding the chemicals would get pretty hot during use....
And they stayed hot for a while even after they stopped producing O2, which many a sailor discovered to their misfortune.
WWG1WGA
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)