Negative pressure possible with passive intake?

I have a 2'x2'x4' tent and a 100 CFM fan with a roughly 20"x6" passive intake slot. Will this produce negative pressure, or will the passive intake have to be sealed off. If it has to be sealed off, will the exhaust be able to circulate air efficiently? Ultimately I am aiming to attach a carbon filter to the exhaust to reduce the smell. I have a small 33 Watt fan inside as well. If I am missing any vital information, please let me know.

Thanks for the help.
 
Assuming I don't have the option of doubling CFM, am I better off closing the passive inlet and forcing air through small cracks?
 

Seth Rich

Active Member
Assuming I don't have the option of doubling CFM, am I better off closing the passive inlet and forcing air through small cracks?
You could try reducing the size of the passive intake inlet by half. Find a way to cover up half of it and see if that helps you get better pressure in the tent.
 

.Smoke

Well-Known Member
Your fan and inlet will both be fine as is.
You stated your tent is 2'x2'x4', which is 16 cubic feet. Your fan moves 100 cu. ft per minute.
Your air is refreshed every 9.6 seconds.

I run a 4'x8'x6.5'ish with a 740cfm exhaust. Making my turnover rate roughly 17 seconds and my tent walls are sucked in tight with 2 of those sized passive openings.
20200328_051050.jpg
 

Renfro

Well-Known Member
If my suspicion is correct, your fan is not a centrifugal type, but an axial type and those fight static pressure poorly. So restrictions will kill it from 100 CFM to about 10 CFM.

To pull a good negative pressure you will need a centrifugal blower or at least a mixed flow.
 
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