Greater than 1001 CFM

Fans rated above 1,000 CFM — large inline fans, wall-mount and drum fans, shutter exhaust fans and greenhouse circulation fans.

Size the fan to the room, not to the light. Start by dividing the room's volume in cubic feet by the number of minutes you want a full air exchange to take, then add 20 to 40 percent back for the carbon filter, the length of the duct run and every elbow in it. LED fixtures put less sensible heat into a room than the HID lamps this guidance was originally written around, so an LED room of a given size usually lands at the lower end of the range. Our guide on how to find the right CFM fan walks through the calculation.