Extra air inlet holes (20) are distributed over the front and side walls (26.28) of the casing of the warm air fan (11). These holes are connected to air guides (35,63,67) formed in the casing of the warm air fan unit. The air guides are rings connected together by webs to form circular inlet holes. The rings have different diameters -the smallest rings being near the end walls of the fan. The fan wheel (44) lies after the heater (37). After the hood has been connected to the fan unit the fan wheel lies inside a continuation of the hood.
