Multipurpose air heaters with a heat exchanger are designed to generate a coolant (clean heated air) up to a predetermined temperature (max 120°C), to work with dryers with the efficiency of 15 – 50 planned ton/h, to heat industrial premises. Air heaters can operate on the following types of fuel: (T) firewood, forestry and woodworking waste, (ZH) diesel fuel, light fuel oil, oil, (G) natural and liquefied gas.