VENTILATOR

PROBLEM TO BE SOLVED: To secure a regular ventilation amount after power failure in a direct current power distribution system.SOLUTION: A ventilator is composed of a power supply detecting means 2a for detecting a state of input voltage at power failure or at power recovery, a storage means 3a for integrating the time from power failure to power recovery of a direct current power supply by signals determined to be power failure and power recovery by the power supply detecting means 2a, a power supply battery 4 for integrating the time by the storage means 3a, and a power recovery control means 5a for calculating an insufficient amount of the regular ventilation until the power recovery by the integrated time of the storage means 3a and driving an air capacity of a fan motor 1 in response to the insufficient amount. By this, the power recovery control means 5a calculates the insufficient amount of regular ventilation unable to be carried out during the power failure from the integrate time during the power failure, and the air capacity at power recovery of the fan motor 1 is increased in response to the insufficient amount of regular ventilation to carry out correction operation of ventilation.