# how big of a passive air intake



## warfish (Feb 4, 2010)

I am wondering if there is any formula to follow on passive air intake size vs your exhaust size.  I am using a 424 cfm fan for exhaust out a 6" duct.  My passive air intake is 10" x 9".  Just wondering if this will be large enough or if I might be starving her for air.

Warfish


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## LEFTHAND (Feb 4, 2010)

warfish said:
			
		

> I am wondering if there is any formula to follow on passive air intake size vs your exhaust size. I am using a 424 cfm fan for exhaust out a 6" duct. My passive air intake is 10" x 9". Just wondering if this will be large enough or if I might be starving her for air.
> 
> Warfish


 
*how big of area is this hole supplying air too?? *
*but i would say yes other wise man.. thats a decent size hole.. with some good suction... shouldnt have a problem..*
*LH*


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## warfish (Feb 4, 2010)

Thanks LH   I am thinking it is plenty as well.  Guess I am just trying to maximize the conditions.  The room is about 220 cubic feet of air space.


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## LEFTHAND (Feb 4, 2010)

warfish said:
			
		

> Thanks LH  I am thinking it is plenty as well. Guess I am just trying to maximize the conditions. The room is about 220 cubic feet of air space.


 
*oh yeah you will be good.. just keep an eye.. for first signs..*
*but i cant see any problems ocuring..*
*LH*


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## PencilHead (Feb 4, 2010)

Warfish, this might be as crazy as checking your gasoline level with a match, but I get in my grow room and close the door, listen to see if the fan is bogging down.  If you can't here it from your room, get someone else to close it off while you listen to the fan.

I'm sure there are far more technical solutions that involve slide rules and secret formulas and what not, but I go caveman simple when I can.  If my fan is happy, I'm happy.


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## buddog (Feb 4, 2010)

Should be good warfish i got a little over 600 cubic feet with one 6 inch 448 cfm vortex fan with two 6 inch passive openings in the floor . I have very good speed controller for the fan in winter only 20 % & summer 50 % of the fans speed is all i use .And u cannot hear a thing love it.


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## umbra (Feb 4, 2010)

3in ok f'up ok


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## dman1234 (Feb 4, 2010)

mine had to be bigger, like 12 inches high by 24 inches wide, 6inch vortex and the temps went to high, once i me intake bigger no issues, go by temp and you will be able to tell.


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