Thanks for the fast reply. Forgot to say, the entire room is 120 sqft with a 9ft ceiling. 29ft for veg an 50ft for flower. I figure, but very unsure, if I can exaust 300 cfm then that covers all of the air in the room every 5 min. Is that enough I wonder. I would ask the hydro store folks but they always up sell me. Cant blame them.
The simple answer is "no", that 300CFM fan isn't gonna do shit for you.
I'd shoot for a
minimum of 1X air exchange per minute - that means you need to exchange:
a) 120sqft * 9' height = 1080 cubic feet * 1.3 (ballpark number to take into account turns in the ducting and the filter) for efficiency loss = 1404CFM for your exhaust (I'd go a little bigger, but that should be okay for ya)
EDIT: there are no hard and fast rules for ventilation; you could get away with something smaller or you may even need something bigger - I'm just trying to ballpark it for you.
Also, Phresh filters are the shit - try hanging a Can and then hanging a Phresh and lemme know which one you like better :winking0067: