The blower, or motorized fan, is one of the most important parts of the entire device, since it’s responsible for sucking up all the greasy range exhaust and ventilating it outside through the ducting. Without a blower installed, the fumes would not be sucked into the hood and would just drift around, polluting your kitchen in the process.
The strength of a blower is measured in CFM (cubic feet per minute), as in the amount of air the fan ventilates per minute, and this is usually the key feature people think about when selecting a blower. However, the blower type is also important.
Rotary vs centrifugal fan
Modern day range hood blowers can be separated into two types, rotary and centrifugal. Your typical inexpensive range hood has a rotary fan, which looks like a fan blade. A centrifugal blower employs a barrel-like design which moves more air and is also much quieter resulting in a lower sone output. Centrifugal fans work very well when installed in ducts, therefore most high end models incorporate this type of fan. Centrifugal fans are the best of the two and should be considered when your budget allows for it.
Aside from the fan design, you also have a number of choices in terms of where you place the blowers. Interior blowers are found inside the actual hood canopy, and are probably the most well known. They are the loudest of the blower types also.
Exterior blowers are placed outside of the house at the end of the duct work. They are installed on an outside wall or on the roof. This type of blower is the best type if you have access to the outside. Although, they are more expensive ,and sometimes have to be bought separate from the canopy, they are the quietest of all the blowers. With the exterior type you have the opportunity to customize your system to meet your needs. Exterior blowers are the type most professional kitchens employ.
Attic and inline blowers
Then there’s also the so-called attic, or inline blowers. These aren’t actually located inside the hood canopy itself, nor are they placed outside the home. Instead they are generally located along the ductwork, and often in the attic, hence the attic name. Inline blowers are a great option if the exterior blower would create an eyesore, such as being mounted on the front of the house, or if it is located next to a bedroom or window. They are more quiet than interior blowers, but not as quiet as exterior blowers. These types also offer the opportunity to customize your ventilation system, and would need to be purchased separately from the canopy. Definitely an option to consider if your application calls for a more inconspicuous blower.