PURPOSE: To prevent a wrong setting of a heat source or the like and further prevent a rapid deterioration of an interior environment by a method wherein an air supplying temperature is compared with a reference temperature to judge an actual heat source, and an air handling unit is operated in reference to a result of judgement.

CONSTITUTION: An air supplying temperature got by converting a signal of an air supplying temperature sensor 6 with an air supplying temperature measuring means 7 is compared with a reference temperature set by a reference temperature setting means 11 by a comparing means 12 and then a heat source is judged. A heat source setting means 8 may set the heat source in response to the judgement, and a control means 9 may control an air supplying fan 5 in response to a set heat source and the air supplying temperature. With such an arrangement, it is possible to prevent a rapid deterioration of interior environment caused by a human error of setting of the heat source, and further it is not necessary to set the heat source to each of the air handling unit through manual operation and thus a quite effective practical air handling unit can be attained.