The reaction principle of warmer is for using the galvanic cell oxidation reaction speed, chemical energy will be transferred into heat energy. In order to make the temperature to last longer, the product uses the mineral vermiculite to keep warmer. Because the product cannot react before use, so bag material is very special, which it constitute the raw material layer and gelatin layer and a non-woven bag. Non-woven bag is made of microporous breathable membrane. It also must have a regular airtight bags - gelatin layer. We should remove the outer bag, expose inner bags (non-woven bags) in the air, oxygen in the air through breathable membrane into the inside. Heating time and temperature are through the breathable membrane oxygen transmission rate control. If the air is too fast, heat will be released immediately, but also it can burn skin. If the air is too slow, there is no temperature. It will become dark brown solid after, which it includes the carbon powder, NaCl, Fe2O3 solid and solid magnesium aluminium salts.