They howl like a sonofabitch, through walls.....unless you get them positioned just right...I would reccomend something with a little more umff for a carbonscrubber. Those nice centrifugal fans are way more expensive but you'll know where the money went. Peace Heres a good one EcoPlus 4" Centrifugal Fan 170 cfm | Exhaust Fans & Circulators
BlazeIdo Reviewed by BlazeIdo on . Duct fans I was wondering if anyone has used duct fans to power their exhaust. I am hoping to get one to put inbetween my growspace and my carbon filter. Does anyone have any tips or suggestions? Duct Diameter:.................... 4" Unit Weight:....................... 2.50 Lbs. Max Boosted CFM:............. 80 Free Air CFM:..................... 65 Amps:................................ 0.30 Housing Length:.................. 6" dBA:.................................. Rating: 5