Passive Intake questions

Quick rundown. I have a metal cabinet approximately 25w x 20d x 68h. I put a 6" Vivosun inline fan and carbon filter in it along the top. It exhausts straight to the outside of the cabinet. The door will be sealed to the best of my ability with some door seals or weather stripping. I need to put some kind of passive intake so the fan doesn't choke. Here is a pic of cabinet to get the idea.



The first question has an obvious answer I believe. In order for the carbon filter to do it's job, the exhaust fan has to run 24 hours a day, correct?

2. I have read that passive intakes should be twice the size of the exhaust. is this factual? I have a 3 5/8 hope saw I plan on using. I was hoping to put 2 holes along the bottom somewhere and then covering it with some sort of filter and screen to block bugs, pests, and light.

Yes, the fan has to run 24/7 and create negative pressure for no odor to escape. As for the size of the intakes, I don't have science to back me up, but the small vegging cabinet I built has an intake vent the same size as the exhaust and works fine. It creates a good negative pressure to hold the door closed. I don't know why it would need to be twice as big, but it probably wouldn't hurt. Just don't make it so big that too much air just falls in and can't create a negative pressure environment.

I believe the issue is that if your intake hole is too small, its going to put strain on the fan. I've read same size to twice the size.

here's some science, I did not follow all the stuff, but it helped me be more confident in my intake sizing.

https://www.icmag.com/ic/showthread.php?t=112862

I have 3 -2 inch? dia inlets, glued insect mesh over

with 6 inch dia extract

works great

that vent link on ic ..best ever

good luck