Fan/Filter run time

Hello All,

I’ve been running my exhaust fan on the same schedule as my lights 18/6, but I’m (actually my wife) starting to smell the plant in other than the grow room.

I was wondering if others run the fan for longer periods, like 24/7?

One other point; one plant, 2 weeks into veg…


Personally I run my exhaust fan 24/7.

Also what kinda light are you using in this picture? The plant looks a little yellow to me but it could be the lights. I’m a newb too so it’s probably fine.

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@happycamper My light schedule is on a 12/12 but my fan is on 24/7 as is my other fan circulating inside the grow tent. No smell, and nothing rots!

Run mine 24/7 in all 3 tents

24/7 for me as well.

24/7 as well.

24/7 but when they were in veg exhaust was on low. Stays on high since flower 24/7.

You should run exhaust fan 24/7 during entire grow
Along with at least in circulation fan in tent the intake fan is optional
Air flow is key in preventing wpm and also helps is developing strong stems and branches
So yes run fan 24/7

@dontellanyone - White LEDs. And, yes, the photo was over exposed. But thanks for the concern.

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Hi @Countryboyjvd1971 - what is wpm?

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Wow, it seems the consensus is to run it 24/7. I guess I’ll be moving some power cords around tonight.

Thanks all for the input.


Yah ok cool, I kinda thought it looked light a light issue. Also, just FYI, I didn’t actually mean to imply that you were a newb like me, it just came out wrong.

Hmmm, guess I had better reconfigure some wiring too. I am running the exhaust fan 12/12 and the three circulating fans 24/7

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Sorry @HappyCamper
Wpm = White powdery mold :+1:


@dontellanyone - No worries… I am a newb :smile:

I have a separate timer for my exhaust fan. I run it the entire time the light is on but have it turn off and on throughout the lights out cycle.
A lot of people run it 24/7 which would definitely help with the odor and it is definitely goodnformrhebplants to be always getting new air circulating. I like having mine turn off periodically to give it a rest and to save on the electric bill.

@HappyCamper think of it this way. They need the light 12/12 for flowering. Flowering triggers the odors associated with growing mj. The smell is 24/7 and the fan should be as well! (I even run my small circulating fans 24/7

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I used a muffin fan that does 200CFM but only uses 36W. It’s typically used for cooling networking equipment, so it’s a little noisy. Probably not any more noisy than other fans. It moves enough air, most fans are turned to low anyways, and if I wanted more, I could order another. They’re cheap on Amazon. I used a rubber coupling to connect the carbon filter to it. Here’s what I got:


Wish I had thought to look up this thread before I bought the AC Infinity T6. Got it specifically to read the humidity in the tent and kick on when necessary, but then I just thought about how I need the negative pressure in the tent to keep the smell in, but that won’t be in play with the fan is off… already threw the box away and everything. Well, lesson learned, when you think you’ve done enough research, you’re wrong.

Everything is situational and has variables.
My humidity is to low even with a humidfior on high.
My first 3 grows I didn’t have fresh air in or old air exhaust and that caused its own challenges (having to flush the room daily with opening a window & door at -40c) struggling to keep the room it’s self below 50RH.

So I bought an AC infinity fan on my second tent setup with an inkbird controller on my old setup.
You have much greater control.
If smell isn’t such an issue for you then shutting it off during lights off is fine if it’s helping you with other issues.
Keeping interior circ fans going of course but I shut mine off for 4hr right now on one and the other is controlled by humidity/temp.