exhaust fan usage?

I am doing a small (2x4x8') closet grow. I bought a 175 cfm vortex inline fan, with a phresh filter. I am curious as to everyones opinion as to how long I should run the fan. Do I run it 24/7? Do I run it for 15 min every couple hours? All opinions are welcome.

i assume you are running hid lighting and the fan is to cool the light and if this is the case you should run it the entire time the lights are on. if the fan is simply to exchange/filter the air it's really up to you. my timer has 15 min increments so i would start 45 min off 15 on and so on, so the air would be injected/exhausted once an hour, which "should" be sufficient for a closet that size. you would have to see what happens and make adjustments accordingly. if it was still too stuffy/hot then you could exchange the air more frequently.

I had to put it in for smell and to keep my temp in check. I am using CFL lighting, but it was still getting into the 90's. I am running the exhaust on the same timer as my lights. I do have a small fan that stays on 24 hours. I am more worried about stale air and/or high humdity. I was just wondering if I didnt have to run the fan the whole time the lights were on, and if I should be running it at some point during the lights out period. Will have to do some experimenting I suppose.