The heating powder is encapsulated in the bag body, which is restricted by the shape of the bag body. The single area of the heating body formed in this way is relatively large, and it cannot be made into a small single body, and it is relatively heavy. To a lesser degree. And because the heating powder formed by iron powder, carbon powder, halogen salt, thickener, and water is a slightly wet powdery material, the cohesion between the powders is weak. When it is packed in the bag, it will be affected by gravity. Sometimes the powder will fall into the bag, resulting in uneven distribution of the heat-generating powder in the bag, and the phenomenon that the lower part heats up quickly and the upper part heats slowly or even does not heat up. Moreover, the particle size of the heating powder material is small, and if the bag body is slightly damaged or the sealing is not tight, the material will leak, and it is very easy to stain clothes or skin.