A flameless ration heater, or FRH, is a water-activated exothermic chemical heater included with Meals, Ready-to-Eat (MREs), used to heat the food. US military specifications for the heater required that it be capable of raising the temperature of an entree by in twelve minutes, and that it has no visible flame. The ration heater contains finely powdered iron and magnesium metals, and table salt. To activate the reaction, a small amount of water is added, and the boiling point of water is quickly reached as the reaction proceeds.