Multiple Light Cycles - Preventing Light Contamination

Hi everyone! Really enjoying reading the threads on here. AWESOME community!

I have a grow room question.

The people I know who grow tend to leave their tents open with a medium sized fan blowing into the tent to stimulate growth and control humid pockets in the tent. If you only had 1 grow room with multiple tents and you were growing plants that were NOT autoflowering then that might be an issue if they’re all on different schedules. For example - let’s say tent 1 is veg and tent 2 is bloom. During the “night” when tent 2’s lights are off there will be light contamination getting to the plants from tent 1’s lights if all of the tents are open. To solve the light contamination issue one might decide to zip up the tents. Right?

If you zip up the tents and have a 6" fan with ducting and a charcoal filter (to help with the smell) exhausting into the grow room (essentially just recirculating the air to hopefully scrub the smell) would that work? Let’s say the fan is exhausting out a hole in the top right of the tent and you open an inlet for fresh air to be pulled into the tent on the bottom left. Remember - the door is zipped shut. Would that allow enough air to flow through the tent to stimulate growth and take care of excessive humidity? Will exhausting into the grow room (pulling the air through a filter) take care of the smell? Is this just a bad idea?

Looking forward to being able to contribute soon!

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I don’t think you’ll find anyone here who leaves a tent open so a fan can blow air in through the main doorway - that pretty much defeats the purpose of a lightproof tent, and gives you little control over the environment.
There are different sized fans for different size tents, but in general a 6" 350-400 CFM fan is sufficient for a 4x4x6 tent.
A carbon filter will manage the smell quite well.
Not that you have to set yours up this way, but here is a diagram of my ventilation setup:

You will notice that I have both an inlet fan and an outlet fan. I do this for more temperature control, but you don’t necessarily have to.

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AWESOME! Thanks! Only your intake fan has a speed controller?

Keeping the tents open is just the way my peeps have been doing it… but they have multiple rooms and only do 1 grow per room. I have multiple grows in one room… in multiple tents. Not such a big deal if I’m doing all autos but I’m eventually wanting to try some more elaborate training with photos that’ll put the tents on different schedules.

If my exhaust just exhausts into the room is that sufficient? I don’t really have a way to get it outside.

My tents are exhausting into the same room they are in. While not ideal it has been working. If it were going to a different room or outside I would have better odor control and fresher air for he little ladies.

Welcome to the forum!

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Sure, that will be fine. That’s how mine is set up.

And yes, I have the speed controller on the intake fan only. The exhaust fan runs at full blast all the time.
When it’s cold (my tents are in a basement) I leave the intake fan off. As things warm up, I speed it up as needed. You can do the same with a single fan and controller.

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Nope i dont leave tent open. All my fans do the work that requires the airflow needed to keep a controlled environment.

Just remember you want more air sucking out then you do pushing in.

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That’s a good point. With my dual fans, if I have the inlet fan on high (only needed a couple of times when it got really warm) and the tent puffs out instead of in, it does produce a smell in the room. The positive pressure is pushing some of the air through the zippers and cord pass-throughs instead of through the carbon filter.

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Good rule of thumb … when tent is zipped up, have tent sucking in not puffing out… keep tweeking it until that is achieved

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You Can also get pole fans for your tent and the make a slim style fan for the floor i have a 6 pole fan aimed at the top of the plants and a 10 in fan on the floor to. This with a 440cfm 6in exhaust fan keeps me from getting bud rot

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Yup, don’t leave your tents open when multiple tents are in same area of house. If you run passive intake, build light trap around the intake of your tents. In most cases a fan and filter on exhaust will keep light out there, but double check it to be sure. If you run intake and exhaust fan, you can usually add a duct elbow or small piece of insulated duct to your intake to keep it light tight.

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Thanks for the insight and thanks for the warm welcome! Bubblehead eh? Same here!

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Excellent!

That makes perfect sense! Thanks!

that would be your air ventilation (exchanging the air 0.5 to 2 times a minute)
like Thc said… the tent still needs air circulation inside,
this is done with oscillating fans and/or small axial fans.!

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Thanks for that! You don’t feel the intake and exhaust fans provide enough circulation by themselves? Or is it a “better safe than sorry” approach?

Yes the fans are good but if you have alot of big buds why take a chance of something bad messing up your hard work my 2 extra fans were 25 dollars for both it’s a little like extra insurance

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