a roof mountable kitchen grease exhaust blower is constructed with hinged housing elements which can be raised for easy service access to all parts of the unit . redundant blower drive motors are provided either of which can be easily engaged to the blower wheel in the event of failure of the other . a blower wheel drive belt is equally engageable to either drive motor and changeover from one to the other is easily and quickly made by minimally skilled personnel . the newly engaged drive motor is enabled by a power select switch at the blower control panel .