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Air Circulation During Dark Period


New Member
I've kept my exhaust fan running on a slow speed during the dark 12 hour period to keep air circulating to reduce humidity. I've seen comments where other growers turn their circulating fans off, stating that the plant is dormant during the 12 hour dark cycle, and follows the natural effect of less wind at night.

I'm hoping that someone that has better knowledge of the biology of MJ can shed some light on the subject. Thanks in advance.


Member of the Month 3rd Place Winner (Dec 09')
I plan to keep mine running 24/7. The way I see it the plant(s) alive and "breathing" even while resting. The more fresh air the better. If you are working in a big open room it's not going to be as important. I am using a 4x8x7 tent which is only 224 cuft of space. Minus the space occupied by buckest and equipment does not leave much air.


New Member
Depending on your humidity levels its a good idea to leave a fan going for the last 4 weeks of flower. Its pretty easy to end up with a bud rot problem if you have good tight buds.


New Member
Thanks for the input! Looks like I'll keep the air flowing:cheer:
All plants aspirate/breath during the dark hours that go's for all kinds of plants I keep fresh and circulating air on the plants 24 hours a day and I have never had bud mold or rot........:rasta:


New Member
best way to keep your room vented while going easy on our resources and pocketbook is to hook your intake fan up to a interval timer or a thermastat. take for instance i have my entrance come on evey hour for 15 minutes while my exit fan is hooked up to a thermastat which is set for the lowest setting during the light period so its always running while the lights are on than during the night i have it set at 70 so that it turns on every once and awhile i always keep on 18" oso. fan goin for are movement, but it depends on alot your square footage, temp, number of plants and ect


New Member
what if it gets too cold when the out take runs during dark time.my room gets about 58 deg if i leave my out take running.i think that might be just a bit too cold.i do have 2 -16in oscillating fans that run 24/7.they keep the air moving pretty good.they pull fresh air in through my intake vents.works quite well.no signs of mold or rot.


Member of the Month 2nd Place Winner (Feb 10')
Hey timmy,
i would turn the oscillating fans off during dark period and just let the exhaust fan work its charm. Whats the RH during lights off?
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