i could put the exhaust on timers and have them turn off while i pump the room w/ co2.... when i pump the room full, how long should it sit w/o a fan... or should a fan always be on...

today i went and bought the little 12gram canisters from walmart AND blew 2 of them into my 4x4x7 homebox. i turned the exaust off and the occilating fan off. and it been that way for 2 hours now... got a thermometer and its hold steady at 84* at the top and 83* at the bottom.