Using a 4" Comp Fan for Exhaust in my growbox. With 8 CFL 2700 lights...24/7 Should exhaust fan be running 24/7 from seedling?
Are you using your exhaust fan to "blow" on the sprouts? if so... I say yes! Especially with the CFL's which are prone to stretch towards the lights, causing them to have lanky/long stems. The fan blowing on them will help "force" them to have stronger stems.
Have a little 4" Clip on Fan inside of the growbox near the intake which I can use...the exhaust fan will be pushing air out...
Keep the fan on 24/7 that way you always have fresh air coming in, if you let the air get stagnate the plants eat up all the co2 available to them. Keep the cfl's as close as possible to the plants without touching because they don't get hot, this will help keep the stretching down. Also have grown with cfl's myself and I'd recommend using scrog that way you can keep your canopy level and the lights close without having to move the lights to much. Good luck OP!