I have 9 x 11 grow room, with 6 gallon humidifier. I noticed when my 8 in inline fan Is on, it reduces my humidity greatly. I can’t get it to the exact humidity that I want, Are use the same in-line fan & humidifier before and never had this problem

this is a first. My question is does a closed off room with CO2 have to have an in-line duck fan?

1 Like

Longtime no see.

I’m confused because you’re saying the room is sealed, but you’re venting. Can we straighten that out first, before we address the humidity swings? In the process, we might even solve the humidity.

Do I need to vent? It’s my first time doing hydro with a sealed room

I’m confused because you’re describing an in-line fan, you’ve clearly got a carbon filter ducted to something, but I can’t tell if you are actually venting.

You can just post a photo from a different vantage so we can see the filter/duct/humidifier/AC/etc.

Edit: feel free to photograph each wall from the opposite side.

You gotta position the equipment in the room to travel better

If your creating humidity and exhausting heat don’t position them so close.

You’ll want to create the most area between the exhaust and humidifier

That way it’s coming in from one side and pulled out from the other

Make a diagram of your room and plan it out so you can have an idea of how things will move


In my understanding of a sealed room, you do not vent, hence the phrase, “sealed room”.

I would not give advise on co2 room because I don’t know. @Myfriendis410 @peachfuzz may be able to help or recommend someone that does. If you are using a vent, co2 is useless because the vent will pull it out.

If your AC only has one outlet, the room will have to have an inlet. One option would be to have an AC with an inlet and an outlet, or a mini split, or a window unit. It will accommodate a sealed, or vented room.
My problem was finding one small enough for my room.

I built a 5’ x 10’ room. During the construction I had to figure all growing scenarios.
I have two 6” inlets at the bottom, and two 6” outlets near the top. One outlet is blocked off with a 4” exhaust fan but have yet to use it. I have a 6” exhaust fan mounted to the ceiling and the filter mounted above my lights to help pull the heat out.

I am able to control the adjacent room with home AC. It draws the cool air in that helps some. I control the humidity by hooking a hose to my dehumidifier exhaust in the adjacent room and running it to an inlet of the grow room.

I personally have not had too much of an issue with lack of humidity since running RDWC. When they are small, in my case, the exchange of air is not as important until the get bigger, (only two plants).
So I was able to adjust it with the exhaust fan.

Hope this helps in some way. If you have any question, don’t hesitate to ask.
Good luck.


Plants don’t need to be in a high CO2 environment 24/7 but intervals during veg and flower IIRC. The problem is as stated, needs to be a sealed environment while this happens and heat/humidity rejection has to be very high (again with a closed system this is expensive). Along with that, anywhere from around 1,000 µmol up for light for it to be beneficial.

It’s highly technical and too much for this stoner to GROK haha. But there’s lots of growers on YouTube that kill it.


You don’t need to exhaust room if you can maintain proper temperature and co2 levels. No exhaust and intake would be a sealed room. Would require most to have air conditioning and a source for co2 that are proportionate to loading of the room.


Nice set up!

Took me a year to upgrade my 2x4 , some just land with crazy set ups :grimacing:, love hydro looking good :relieved: