how do underwater flares (or matches) maintain a flame or light when they are surrounded by water?

Question

Just watched Crawl (2019) and got me thinking.

Edit: i should clarify, why do they not extinguish like a normal flame.

In: Technology

Answer 1

We’re used to seeing fires that get their oxygen out of the air, but that’s not the only way to do it. If you heat up a material with a lot of oxygen in it, like a sulfate, a phosphate or a nitrate, it can break down and release oxygen gas. So a mixture of, say, magnesium metal and some kind of nitrate, could keep itself going underwater. The nitrate breaks down and releases oxygen, then the oxygen helps burn the magnesium.