My granddaughter was in the kitchen waiting for a civilian version of a MRE to heat up and it began to steam releasing a slightly irritating vapor that gave me a taste of iron in my mouth and it also set off a CO alarm. I was wondering what in the steam could have set off the alarm.
I found this info about ration heaters in Wiki. “Ration heaters generate heat in an electron-transfer process called an oxidation-reduction reaction. Water oxidizes magnesium metal, according to the following chemical reaction:
Mg + 2H2O → Mg(OH)2 + H2 [+ heat]
This reaction is analogous to iron being rusted by oxygen, and proceeds at about the same slow rate.
On their own, the reaction between magnesium and water is too slow to generate usable heat. To accelerate the reaction, the developers (see U.S. Patent 4,017,414 and U.S. Patent 4,264,362) mixed metallic iron particles and table salt (NaCl) with the magnesium particles.
Iron and magnesium metals, when suspended in an electrolyte (such as salt water), form a galvanic cell—a "battery"—that can generate electricity. When water is added to a ration heater, it dissolves the salt to form a salt-water electrolyte, thereby turning each particle of magnesium and iron into a tiny battery. Because the magnesium and iron particles are in contact, they become thousands of tiny short-circuited batteries, which quickly burn out, producing heat in a process the patent holders call "Supercorroding Galvanic Cells".
U.S. Patent 5,611,329 uses a powdered magnesium-iron alloy, consisting of 95 % magnesium and 5 % iron by weight, and discloses a heater consisting of 7.5 grams of this alloy, and 0.5 grams of salt. Upon adding 30 milliliters of water, this mixture can heat a 230 gram meal packet by 100 °F in about 10 minutes, releasing approximately 50 kilojoules of heat energy at about 80 watts.”