Heating system and method for influencing air flows in a heating system

The air heater, especially for a vehicle interior, has two heater units (10,12) with an air flow path between them. An additional fan blower (50) generates a flow from the second to the first heating unit, into a mixing chamber (14) with air channels (40), when activated by a signal from a control unit. An air intake (36,38) is at each heating unit.