how many cfm's do I need

OK, so I've been seeing a lot of different answers for CFM requirements. Some people say be able to move the air out once in 5 minutes and others say 5 times in one minute.

I have 184 cubic feet and was thinking about using a 475cfm fan but didn't know if that was TOO much because I heard a story from a friend that his setups walls were sucked in because of too much negative pressure.

Anyone have some good info on this.

I think your friend is full of shit possibly. Negative pressure from an extractor fan sucked his grow walls in. Full of shit or growing in a cardboard box maybe.

There is no real answer as to exactly how much, if you've negative pressure, then you're on the right track. If you think the pressure is too great, then you can simply add some bends to the ducting to increase the air resistance there, or you can increase the number of or the size of the intake.

thank you, I didn't think that a few fans could do that to a grow room haha. I just wanted someone who knows what they're talking about to reassure my assumptions

are you filtering the air or just circulating it? filtering you want at least 3 times per minute to clean the air.... and it has to match with the carbon filter specs...