4" inline fan

Hey guys. Long story, short... i build a diy grow box 2x2x6, and was planing to use 3x noctua nf-p12. The pc fan has a pressure of 1.2-1.7mm H2O. I am just really beginning to doubt the efficiency when i add a Carbon filter. I havent drilled the holes for the fan yet, so i wont have to...

Hello All. I'm a first time grower, I am building a 6x6x7.5 feet grow room in our basement. My question is, will a 4" inline fan bring in enough fresh air for the girls? I will have a 6" exhaust with carbon filter. It is 270 Cubic feet. Thank you for your knowledge Have a great day to all!