using a fan durning flowering

[stinkyattic]

yes.
not just one.
I prefer multiple smallish fans placed strategically around the grow area to move 'used' moist, CO2-poor air towards the exhaust, and keep a constant air movement around the plants, including low down among the pots where dieases can hide.

[Dutch Pimp]

...another method is to pump A/C air into grow room/closet....using dryer duct hose (4 inch)...attach to the central air floor opening...(cardboard box, over opening, hose attached to box- the other end blowing between light and top of plants)...it works in the winter time (for heat) too....:thumbsup:

I could control heat and humidity with the thermostat...:rastabanna:...using a battery digital thermometer (one that records high/low readings) at various places around the plants.....:thumbsup:...enjoy....