i'm building a flowering room in my basment. it will be 6'6"x7' and it will be about 6'6" high. passive air intake(haven't cut that out yet) and for now it will have 1x 400watt HPS light with an econo wing hood. i'm going to build a can filter out of some duct parts hardware cloth( its small fencing) panty hose duct tape and aquriam carbon,i got the original disign from overgrow before they got closed, glade i pasted it. my question is what fan and filter size to go with for my room. the local grow shop sells 2 fans that i'm considering there both inline duct fans by active air. there's the 4" 165CFM and the 6" 400CFM i'll be building the filter to match the fan so 6" reducing to 4" for the 4" fan or 8"reducing to 6" for the 6" fan which fan and filter combo do you think i need for my room there's also an 8" 720CFM fan but i'm not sure if i can build a filter to match it.(pantyhose only stretch so far) o and i know my lights not enough for this size room i won't be using the whole space for growing only about 4'x4'(16 12" round buckets) for now till i have more money. thanks for any and all help.
For your growing space the 165 CFM should suffice. The only reason I would consider going with the 400 in a space that size would be if I thought I might run an air cooled hood in-line with the filter and the fan. Even then the 165 might work out. I've always just tried to adhere to the rule of complete air exchange in 5 minutes and the 165 in that space should work fine even with the restriction created by the filter. 6'6"*7'*6'6"=295.75 cubic feet divided by 5 minutes comes out to 59.15. That's my reasoning anyway.
On a side note be sure to rinse and dry that activated carbon thoroughly before you put it in your filter. I got a little lazy building my filter and only sifted some of the carbon. The fan and filter are mounted inside my closed door so when I shut the door I got a black carbon cloud straight to the face. Pretty funny but not so awesome at the time.
thanks i was thinking along the lines of exchange every 5 mins but i wasn't sure how much the filter would affect my fans CFM.