Wall mounted fans are just that, a fan which is mounted to the wall or installed in a cavity through the wall. Although one style is for general air circulation and the other is for exhausting air from the room to outside, they both serve their purpose.
A wall mounted fan which is used for air circulation is usually mounted directly to the wall and plugs into a standard 120 volt wall outlet. There are other models, usually considerably higher capacity that are mounted through the wall, the through the wall fan can be either pulling air in from the outside to cool a room or pulling stale air and odors from a space and blowing them outside. Wall exhaust fans are used in kitchens and in industrial applications.
Wall exhaust fans consist of a propeller style fan blade, this blade is mounted to a central shaft which in turn is mounted in bearings. Connected to the end of the shaft is the drive motor, this entire fan blade and fan drive assembly is them mounted in the fan box which is then installed in a pre-prepared wall cavity. The fan is connected to an electrical power source and a switch.
For a simple kitchen fan it will always be installed in an outside wall, the switch is normally unique to the fan and not hooked up with the kitchen lighting. This electrical arrangement is ideal because there are many times when people are in the kitchen but not cooking so there are no odors to eliminate. As the fan is half inside and half outside it is important that there are louvers which open and close as the fan is turned on and off. The louvers are usually light metal slats which open under the force of the air, when the air stops, the louvers close.
Wall exhaust fans are popular in industrial applications, especially in areas where there is high heat or chemical fumes. Although they are installed in a similar fashion, always on an outside wall, in some cases they do not vent the air directly into the atmosphere. If the fan is only eliminating heat, yes the vent is directly outside but if the fan is pulling paint overspray for example from a paint booth, the fan will exhaust through filters.
