The Blower Fan
The fan is the heart of a range hood, and the larger the fan, the better it captures the fumes to distribute them over a wider area. For an electric range, a basic fan size should be rated at 100 CFM (cubic feet per minute) for each 12 inches of range top.
An example would be that a 40-inch range top needs a fan with a minimum rating of 400 CFM. Gas stoves require 100 CFM of fan capacity for every 10,000 BTUs, so a 50,000 BTU stove would need a fan rated at 500 CFM.
However, larger fans will make more noise when running, so check the sound or sone rating of each fan. The closer to zero the sone rating is, the quieter the fan will be when running.
The Grease Filter
The grease filter will look like a steel mesh. The mesh captures grease particles so that they won't be exhausted back into the kitchen.
Air passes through the grease filter, and as the filter becomes clogged with grease, it loses its effectiveness. Depending on your cooking habits, clean the grease filter monthly by soaking it in a dishwashing detergent solution to break up the grease particles, and then rinse it before replacing it.
The Charcoal Filter
The charcoal filter traps cooking odors and sits behind the grease filter. It cleans the air before it is exhausted back into the kitchen.
Charcoal filters cannot be cleaned. Depending on stove and oven usage, they must be replaced approximately every three months to remain effective, and more often if the range gets heavy use.
Keeping it Clean
Because a nonvented range hood recirculates the air from the range, it will build up grease, grime and dirt faster than a vented type. The cleaner your nonvented range hood is, the more effective it will be.
Dishwashing solution and a brush will get into cracks and crevices and remove grease buildup from exhaust grills. Consider this a monthly task every time you soak and rinse the grease filter.