I have a stealth closet grow and right now I have a 4" duct with DIY carbon scrubber with a pc fan blowing the air. It just doesnt seem like enough. I was wondering if the 4" inline duct fan that u can get a homedepot is loud or not. Of if there was another option for me.
i've got three of those same inlines, two 6"ers and one 4"er. the fours aren't that loud at all, but don't push much air. the 6" ones work good, but do make some noise. not too much louder than a loud computer though.
I have 3 6" inline duct fans running all at once in my current grow (the ones from home depot about $35 each) they are not that loud at all. one for intake, one for exhaust, and one hooked up to my air cooled light. they work fine for my purposes. But you said you have a DIY carbon scrubber, i'm betting the inline duct fan won't work for that. they don't build up enough pressure and would probably not push any air through the filter, making it useless. it would be just like blowing it at a wall. you are going to have to buy one of those really nice vortex ones, (if you wanna get the job done right) which run around $150-$400 depending on size. those are also much noiser. but with any type fan, if you add on a length of tubing (if not already there) on both sides of the fan, it will work just like a muffler for a car and reduce the noise by a noticable level. they also make "fan muffler's" but deffinately don't use one of those unless you buy the really nice "expensive" fans, because they will also reduce the pressure or air flow.