Vent ports vs complete light blocking?

Hi All,

If we care about light not entering or escaping the tent, how do we leave vent ports open at “night”?


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Someone suggested to me to take that flexible duct like what you use on your filter/fan and make small “j” bends in them to stop the light and still use the vents. I honestly think i am gonna buy some 8" galvanized duct elbows and just stick em in the sleeves and draw the string tight around it…and may just keep em outside the tent so i don’t take up room in the tent :man_shrugging:

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Just remember, you don’t have to cut it out completely. 95-98% light reduction will work. The suggestion above will work great. if you want a quick fix, buy a roll of 2mill plastic, cut a 3 ft long piece, roll it up into a tubular fashion, and duct tape it to the vent hole. This will allow air to escape but cause enough of a fold in the plastic to not allow enough light in to cause irreparable damage.

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You know that cheap sponge like filter used on window Air Conditioner vents? It’s almost
foam like?

Well, I managed to cut a piece of that material and place it over the vent and secure it in
place with push pins. Blocks out all light AND catches those very thin cat hairs that
get into your tent no matter what you do.

As long as your tent isn’t in direct sunlight those vent ports don’t allow for a whole lot of light to get in. If you find to be having this issue, turn or move your tent out of the suns direct shine and into a shaded area of the house. OR make sure your night and day hours are matched with the rising and setting sun.


You really do need to make a space light-tight. Some genetics are more forgiving than others, but why tempt fate?


What does the moon reflecting the suns rays put off? If I’m not mistaken it’s less than 146 par?ppfd? And it’s higher on the UV or blue spectrum which brings down cellular development, this is mimicked by reflection of (physical) light in a duct setting, either in the snake pattern that was previously presented or in a light screen which in forth; a black 2 mil plastic, rolled in a cylinder or conical fashion, with an exhaust fan ( not on full blast ), could create enough light mitigation to allow for proper growth. So I believe keeping light tight is useless at points, due to the evidence of moon light being available.

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I don’t think so. Every report I’ve seen suggests even a full moon on cloudless night measures less than 1 lux. The conversion of 1 lux to ppfd is .02 umols/s/m2. That is basically no measurable light intensity.

Cannabis is c3 plant, doesn’t need dark at all for proper growth. It needs dark to move into flowering phase of its life. Once it starts this process having that dark time interrupted can confuse it’s cycle and potentially cause it to self pollinate. This is the reason for the questions and solutions the other members have provided. Moonlight not having any measurable radiometric energy at the plant is the reason outdoor plants are unaffected. But artificial light is pretty much a different animal.


Just for comparison, 1 candle puts out nearly 11x more lux than a full moon.

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That’s about 1 candlepower right?

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Yeah, 1 foot-candle.

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But can the horsepower run a headlight?

I use a flexible air duct with a couple bends in it and one of these on the outside of the tent clamped onto the duct.

With a quantum meter I receive zero umols

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Hydrofarm ACBS6 Bug Fan Exhaust…

Share this item This works for me

That looks perfect for an air intake port in a stud wall.

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I dont get it.

LoL sorry if your not laughing but for some damn reason I am.

I have so many holes in my tent you would be laughing also. Damn I need to start fixing my tent…

Anyways if you use silver hard pipe to duct into tent be sure to spray paint it black inside. Also have enough curves in it to stop light. An s curve works

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I made a sort of baffle out of cardboard that blocks most light around the vent but has openings on each end for air. It seems to keep it pretty dark inside.
(Peaking my head in during lights out and trying to see anything.) I also blocked all windows and put up black plastic sheets to block any possible direct light if someone turns on a light.

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