A heater is an energy conversion device that inputs energy into the heater in the form of chemical energy from fuel, electrical energy, and thermal energy from high-temperature flue gas. After being converted by the heater, it outputs warm air, hot air, and high-temperature air with a certain amount of thermal energy. A heater consists of two main parts: a combustion system and a fan. The combustion system generates enormous heat, which is then blown out by the fan.