AC Infinity CLOUDLINE PRO S12, Quiet 12” Inline Duct Fan with Speed Controller - EC Motor Ventilation Exhaust Fan for Heating Cooling Booster, Grow Tents, Hydroponics

When it comes to safety, overkill doesn't exist. I've got an 8 in fan that does about 800cfm for my enclosure (4'x6'x3') and honestly sometimes I feel I should have gone larger lol When it comes to airflow, go as big as you can (like this one that does 1600CFM) I will say though that getting a fan that actually does it's stated CFM was pretty tough (which is why the ones I linked are the same brand just different sizes) but the linked ones were actually great and do what they say they will.