Get that fertilizer scent under control! Airtech not only has the solution - they offer very affordable replacement cartridges (filters). 

Airtech has developed a unique pre-exhaust odor control filtering system for use with your exhaust fans. Most carbon filters are commonly used as an exhaust intake, or recirculating polishing filter. But Airtech's Carbon filtering system provides a flow-through design that is unique only to this filter.

The fan CFM requirement is intended for a centrifugal type fan to acheive the correct contact time for the air passing through the carbon. With the correct contact time, the air is exposed to the carbon long enough to insure that the air is cleaned sufficiently. The CFM's are important to acheive the correct pressure to utilize all of the carbon. If you used a different fan, the air pressure passing the filter would not be enough to use all of the carbon cartridge surface. It may still work with a less powerful fan, but the carbon may not last as long as it should. A fan that was too powerful would not allow enough exposure time for the air to be cleaned properly.

Carbon 1: Handles 1000 watts of lighting with 200 CFM (holds 1 cartridges). Connects to 4" ducting.

Carbon 2: Handles 2000 watts of lighting with 400 CFM (holds 2 cartridges). Connects to 6" ducting.

Carbon 3: Handles 3000 watts of lighting with 600 CFM (holds 3 cartridges). Connects to 8" ducting.

And then there are the big guys:

Carbon X: Handles 6000 watts of lighting with 1000 CFM (holds 4 cartridges). Connects to 10" ducting.

Carbon XL: Handles 10,000 watts of lighting with 2500 CFM (holds 4 cartridges). Connects to 12" ducting.