Exhaust fan and carbon filter size

I'm looking at exhausting 2 rooms individually, each are approx 2'x2'x4'
Would a couple of DIY filters like found here: https://www.rollitup.org/do-yourself/101248-best-diy-ez-walmart-carbon.html
with a 120mm 74cfm computer fan for exhaust work? 1 fan for intake and 1 for exhaust + filter on each room.

Or would I need something bigger?

Ideally you'd want something bigger for that grow room. a 74CFM fan connected to a filter will not really work all that well.

This would be better: 1 intake fan @ 74 (higher if possible); 2 exhaust fans (1 stacked on top of the other, so 240mm tall) and have the filter hooked up to both those fans for a CFM of 150. This also creates a negative pressure in the grow room to expel smell more efficiently.

For example Im building a 34"x18"x84" cabinet and am using a 400CFM fan to be used as a cooltube and carbon filter fan. Im installing 3 120mm 100 CFM PC intake fans. Should do the job and then some.

Thanks for the response.

Its a 2'x2'x4' room with a 74CFM intake fan and a 74CFM exhaust fan pulling through a carbon filter as seen in the link from my first post: https://www.rollitup.org/do-yourself/...rt-carbon.html

I have 2 such rooms both with their own intake fan, exhaust fan and filter. You don't think 74 CFM is enough? Each room is only 16 cubic feet.

Also, I'm not sure your assumption that stacking 2 fans on top of one another doubles the output..

1 intake fan @ 74 (higher if possible); 2 exhaust fans (1 stacked on top of the other, so 240mm tall) and have the filter hooked up to both those fans for a CFM of 150. This also creates a negative pressure in the grow room to expel smell more efficiently.

Click to expand...

Also 120mm fans are 120mm in length and width. not height so they would not be 240mm tall when stacked on top of one another. They are typically 38mm tall which would be 76mm high stacked.

any other thoughts?

How loud are fans like this?
http://cgi.ebay.com/6-inch-INLINE-DUCT-FAN-exhaust-BOOSTER-blower-cool-air-/390127340450?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item5ad566cba2

Anyone have an idea in decibels? Would it be a better choice than 120mm PC case fans? I'm just worried it will be too loud.

Get a Panasonic inline or bathroom fan. Ultra quiet and not too expensive if you look around, try Westsidewholesale.com. The 240cfm shows air restriction with a filter on it so call it a 150cfm.