What does cfm mean and why is it important? Room and stove size determine the required rate of air removed, which is measured in cubic feet per minute (cfm).
According to the Home Ventilating Institute, the general recommendation is a minimum of 40 cfm for every linear foot of a range. Usually, an average size range requires air removal at 120 cfm when using an overhead range vent hood.
Recirculating range hoods: This is the most basic but least efficient system. These hoods attach to the wall above the cooktop and pull air through a filter, recirculating it back into the room, often including odors or gases. Filters do absorb grease and require frequent cleaning or replacement. These hoods are easy to install because they don't require ductwork.
Downdraft systems: Such systems are typically part of the range, often on the stove top near the burners. Some stove designs can be retrofitted for venting from underneath. "Hidden" styles remain flush with the cooking surface until necessary. Then, with the push of a button, they rise 8 to 10 inches above the cooking surface. These are best for island or peninsula cooktops where hood installation may be awkward or impossible.
Downdraft units use one or more fans, pulling air through a filter into ductwork (usually beneath the floor or above cabinets, and sometimes out the wall). They need a minimum of 150 cfm. Stove placement is also a factor; wall units need up to 400 cfm; an island cooktop needs up to 600 cfm.
Continued on page 3: Cleaning and Websites