PURPOSE: To unnecessitate protective equipment by providing air conditions with temperature sensors at the return part and blowing parts thereof, and performing the relative operation of return part temperature and blowing part temperatures to detect the failure of the air conditions.

CONSTITUTION: Air conditions 1 are provided with a return part temperature sensor SR at the return part thereof and blowout parts sensors SB1-SB3 at the blowout parts thereof. The respective detection signals are inputted into an air conditioning control device 3. The air conditioning control device 3 computes differences between the inputted return part temperature and blowout part temperatures, and judges whether the computed temperature differences are equal to the failure temperature or smaller or not to judge the existence of failure. The air conditioning control device 3 further computes differences among the blowout temperature SB1-SB3 of the air conditions 1 and compares them with the failure temperature to detect the failure. Failure can be thus detected without a protective device.