Hardware stores such as Lowe's and Home Depot carry a variety of exhaust fan switches. These vendors also sell other fan parts, such as motors and vents.
There are several types of exhaust fans. Wall-mounted fans are installed in an exterior wall, and the air flows from the building out through the fan. Exterior fans attach to the outside of a building, which eliminates interior fan noise.
Bathroom exhaust fans are typically inexpensive fans that remove humid air from bathrooms, reducing the opportunity for mold growth. Kitchen exhaust fans also remove moist air and odors; they are often mounted over stoves.