ventilation question

I'm building a flower chamber out of a two foot wide barrel and I'm gonna be using 2 80mm computer fans for ventilation and I was just wondering if I should use both fans as an exhaust for a passive system or should I have one intake and one exhaust? I'm using 100 cfl watts. Thanks for whoever can help.

I am thinking (my cab build with no ducting yet just vent ports) my exhaust constant (on top) when lights on and intake (bottom) fan hooked to a toggle switch for a boost when ambient temps are higher.Both fans on same timer for lights.These are 80 mm fans too but I was thinking of getting a pc fan with a built in thermistor(usualy used for direct cooling cpu) that ramps up speed above 80F.
here is a basic one http://www.google.com/products/catalog?hl=en&q=pc+fan+thermistor&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&biw=1024&bih=605&wrapid=tlif133403706795810&um=1&ie=UTF-8&tbm=shop&cid=17882405337388896366&sa=X&ei=ZMqDT5mGGqLn0QGAoJHgBw&ved=0CE0Q8wIwAg#

I recommend one in and one out. If you do use both for exhaust remember a passive intake should be three times larger than your active exhaust. In your case 2-80 mm fans would require 6-80 mm holes for the intake. Sometimes this is not practical for smaller closets/cabs. The 1 fan in and 1 fan out method might be better and provide better leaf flutter. Also less light leakage, if stealth is a concern. Happy growing!

Do 1 in 1 out 120mm fans.

one in and one out

Alls I have to work wit r the 80s the barrel is 2 ft wide three feet tall I am running a 68 and a 26 cfl n also a two three ft t8 s will the fans I have suffice

I'm new here. I have a 4" passive intake and a 6" out take with an htg fan and carbon filter with a variable speed control. It totally controls odor. I saw above that the intake should be larger than the outtake? Am I doing it wrong?

odessa said:

I'm new here. I have a 4" passive intake and a 6" out take with an htg fan and carbon filter with a variable speed control. It totally controls odor. I saw above that the intake should be larger than the outtake? Am I doing it wrong?

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Sorry to say but as stated above the optium air flow will be achieved with a 3 to 1 ratio. If this is not practical, make it as large as posible. 4" is to small try 2-4" holes or 1- 8". Ideally you could add a 6"fan on the intake and be just fine. Good luck!