VENTILATION

PURPOSE:To make detection of concentration of contamination in a whole area unnecessary and simplify the control of ventilation by a method wherein the ventilating amounts of respective ventilating areas are determined by the concentration of contaminating substance in a specified ventilating area in case the ventilating area in a room are ventilated by a plurality of ventilating devices. CONSTITUTION:The ventilating airflow amount indexes of respective ventilating devices 12, 14, 18 with respect to the ventilating airflow index of ventilating area of the ventilating device 16 for making the concentration of dust constant in the room 10 are preset considering the circumstance in the room 10. Accordingly, the ventilating airflow amounts of respective ventilating device 12, 14, 16 18 are determined by measuring the concentration of contaminating substance in the ventilating area of the ventilating device 16 and the blade angles of fans 22a-22e are determined based on the indexes. According to this constitution, ventilation may be controlled by detecting the contamination of one area and the constitution of the whole ventilating devices may be simplified.