Magnesium heaters are in use with canned foods in Japan, HeaterMeals, the MountainHouse's Mountain Oven, Hot Pack, rations for NASA and US military and paramilitary MREs (Meals Ready to Eat). They provide a simple a safe method for heating food, with little risk of fire or explosion.
The most popular design uses heating pads made from a supercorrodible magnesium/iron alloy in a porous matrix formed from polymeric powders with sodium chloride incorporated with it or in a separate tablet. To heat, water is added either from an external source or by puncturing/tearing a container of water onto the heating pad. The water dissolves the sodium chloride into an electrolyte solution causing magnesium and iron to function as an anode and cathode, respectively. An exothermic oxidation-reduction reaction between the magnesium-iron alloy and water to produce magnesium hydroxide, hydrogen gas and heat.