The differences and main features of air heaters and liquid heaters are described in use. An air heater is an electric heating device that primarily heats a gas stream. The heating element of the air heater is a stainless steel electric heating tube, and the heater inner cavity is provided with a plurality of baffles (baffles) to guide the gas flow direction, prolong the residence time of the gas in the inner cavity, thereby fully heating the gas to make the gas Uniform heating to improve heat exchange efficiency. The heating element of the air heater is a stainless steel heating tube which is filled with a heating wire in a seamless steel pipe, and the gap portion is filled with a magnesium oxide powder shrink tube having good thermal conductivity and insulation. When the current passes through the high temperature resistance wire, the generated heat is diffused to the surface of the heating tube by the crystalline magnesium oxide powder, and then transferred to the heated air to achieve the purpose of heating.