There are great security risks. Once a fire breaks out, it will cause huge losses to people and property, and if it is put in the yard, it will easily cause coal to get wet and affect its use in rainy days. Coal is a combustible black solid, and its main components are carbon, hydrogen, oxygen and nitrogen. It is formed by ancient plants buried underground through complex chemical changes and high temperature and high pressure. According to formation stage and coalification degree, it can be divided into peat, lignite, bituminous coal and anthracite. Mainly used as fuel and chemical raw materials. Also called coal.