Normal operation and standby local fans were stopped after a power failure, when power is restored, working through local "Inflatable Air Blower" and backup of local fan shall start on its own, it must be manually turned on Local Fan. Heading Face and Other Local Fan ventilation may not work properly with a place to install backup of local fan, but the local fans must be working electric power supply; or working with Local Fan install a local backup of equal ability fan, and can automatically switch. Local Fan failure to ensure normal operation, the backup of local fan is working properly.