To make a warm air heating system compact in size by reducing the dead space in a composite machine.

The depth of the warm air heating system and, at the same time, the dead space in front of a warm air heating section having a smaller depth than an air cleaning section has are reduced by positioning an air cleaning filter 16 below an air cleaning fan 15. In addition, in order to take out the filter 16 through a filter taking-out port 23 on the back of the system, an air inlet for cleaning air provided on the front side of the furnace is constituted in a fixed type. Since the filter taking-out port 23 is on the back side of the system, a simple attaching method using such a manual screw that is not able to be used on the front side of the system from the viewpoint of appearance can be adopted.