# What's the math for proper ventilation

Discussion in 'First Time Marijuana Growers' started by wEEDhEAD1, Jun 20, 2017.

1. I read extraction should be 2/3 times more, I've also read it should be 2/3 times less. I've read it should be equal and I've read you don't need inline at all.

I'm in 4x4x6.5 and I have about 90cfm inline and around 200 being extracted. It's working.
But what is the proper formula (preferably in leymans terms please) I've looked around and gotta confused already :s
Also is the inline need to be more powerful in veg?
I have plenty of circulation in there but I don't know how much to worry about co2 being replaced in the tent...

2. Calculating Fan Requirements

That should help. It also includes how much to compensate for equipment heat as well.

In short, you want 3x your air volume per minute, so.....

4x4x6.5 = 104 cubic feet of air

104cf x 3 = 312cfm

Now add any percentages based off of equipment and lighting and you should be golden!

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3. You want your fan to be able to clear the entire room 3-5 times a minute. Probaly even more then that.

4x4x6.5=104 cu ft

104x3=312cfm
104x5=520cfm.

So you want 312-520cfm.

I think most 6 inch inline fans put out around 440 cfm

4. Thanks a lot dude. I have a Question though! My fan is rated around 400 CFM, I have it controlled to just under half so I'm guessing it omits around 200 cfm atm. This still sucks in the side of the tents giving me negative pressure. I went with the theory if it gives negative pressure it is sufficient! Is This wrong? Should I turn it up?