Active Air Exhaust Fan 

These quiet UL-listed industrial-quality blowers mount easily into the wall and are pre-wired with an 8 ft. power cord. Made by Hydrofarm, ActiveAir blowers are maintenance-free and have a 1-year warranty. 

Air exchange is necessary to help fight CO2 depletion and to cool your grow room down for best plant growth. There's no more efficient way of exchanging air than with an exhaust blower. ActiveAir fans offer a variety of sizes to best meet your needs.

To determine the approximate size blower you need, divide the cubic footage of the grow room by 5. This gives the CFM (Cubic Feet per Minute) of air movement required.

This formula assumes that the blower must be large enough to replace all the air in the room in 5 minutes.

It's better to oversize the ActiveAir blower than getting a one that is too weak to get the job done.

Optional outflow flanges convert the square exhaust opening (outflow) into a 4" round opening for connections to 4" exhaust ducting.

More info from the Manufacturer (PDF format - Lots of detail.)