Whats up GC i went out and bought a 120mm 78 CFM computer fan to use with a homemade carbon scrubber from this thread http://forum.grasscity.com/grow-roo...cheap-easy-efficient-diy-carbon-scrubber.html now i bought a computer fan 78 cfm , and a few posts down he says he uses a 4'' inline duct fan rated 80cfm. my question is will 78cfm be able to push through a few inches of carbon efficiently? because after reading this from another thread i have some concern * \t\t\t \t\t\tThe following is taken from: http://www.alpharubicon.com/basicnbc/safefanwar.htm and explains the importance of a load rated fan, if you plan to use a filter. About the Fan You want a fan that has a "Load rating" on it, it may say something like "Air Flow @ 0.100 Inch Static Pressure 200 CFM"... that means it was designed to pull/push air through a load (Like pulling air through a filter, or pushing air into a saferoom with a positive pressure on it).. the "CFM of air moved" is misleading. A box fan will move 300CFM easily @0.000 inches of static pressure, but with a filter on it, it won't move ANY air... so you MUST have a squirrel cage fan that has a "Load rating" on it.. if it has no load rating, it was NOT designed to move air through a filter! A non-load-rated fan will get VERY hot and may burn up from the extra work it is trying to do while pulling air through a filter. Fan motors designed to work against a static pressure are wound differently than fan motors that simply move air from one place to another. A typical rule of thumb is, "Fan Blades do not work well for pulling air through a filter. You need Impellers (like the fan shown here)". But as I said above, you need an impeller fan that is rated to move air against a load. http://www.alpharubicon.com/basicnbc...fefanwar17.jpg \t\t * thanks if you can help