Need a CO2 guru!

I just purchased a better light that is gonna allow me to push my girls a little harder. Looking around the bunker i got several CO2 tanks(make beer, and have it on tap). Thinking about giving it a whirl next grow but i got questions.

1 how do i keep the ventilation (mainly my AC) from just blowing it out? I dont think i can get the positive pressure down much more and keep my temps where i like them.

2 how long a 5lb bottle last?

3 will using CO2 change where i want to keep my temp, humidity, etc…?

You need to figure out a way to make your space air tight when adding co2 and be able to transfer air when not using co2…
Complicated , but easy…
Depending on your setup and what not…


Meh… i got a tent, its pretty air tight. Problem is the ac unit. It uses an exhaust to co and teansfer heat. In flower it runs non stop. New light will help but unlikely ill get it to where im not turning the tent over several times a minute.

I know there is portable ac unit that is designed with two air hoses. Both can be ran to exterior window. So instead of just having 1 exhaust hose going out, it has another pulling air in from outside. In effect allowing you to maintain air temperature in tent and also help retain co2 in a sealed environment. I’ve never attempted to find one and have no idea how much one would cost. @TDubWilly talked about having one. But I don’t believe he was using it with co2. I think he said that he used mainly to help with controlling humidity in tent.

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Short answer: don’t.

Long answer: NEED HELP! first timer


Yes there is, but it still won’t work for co2 unless it’s modified.

The single hose unit intakes air from within the room, conditions it, then exhaust the heat.

Two hose units are designed to bring in fresh air from outside the room while also taking in air from inside the room. This is the part that needs to be modified. All of the intake to the AC needs to come from outside the room, otherwise you’ll just exhaust your co2 out the window.

To do it right with no modifications at all then you need a mini split AC and follow one if these setups


I remember this now that you linked it. I also know that most home growers have been advised that they really don’t need to use co2. Thanks for the response. :+1:


Thanks for responding. I remember the discussion about this a/c unit wasn’t sure if you were using for co2. I was fairly sure that it was more about controlling humidity and grow environment.

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Im pretty much done with co2.

It works, but for me the return was not worth the time, money, nor effort.

Setup a good ventilation system and good lights and do the other little things right and you will have a successful harvest


As @TDubWilly points out, the way to control temp (and to a degree humidity) in a sealed room is with a mini-split. You have many options in that vein.


Thanks everyone. @TDubWilly. Why you done with it? Because one of my next questions was going to be, is it worth it? All the expense and work and time?

Last harvest on 4 plants i ended up with 22 oz. Im happy with that,bespecially considering the light i used. The new light prolly bump that up some, definately allows to add plants or at least larger canopy. If adding CO2 adds 20 or 30% more then im in, if it adds 5% then not something for me yet.


Like I describe in my linked post, you’d need to push your light well above 700 ppfd in order to see gains from CO2. As long as you’re lower than 1000 ppfd and you’re ventilating well, you don’t need supplemental CO2.

You mentioned a new light. If you wanna share the specifics, we can probably figure out based on coverage, distance, and dim factor, how to run it most efficiently.

I’d keep in mind cost per oz. I don’t know if you have that data from your 22oz grow.

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New light, hlg 600

For starters, I have to go up a 6’ ladder to get to my grow room. I was diagnosed with cancer last year and some things I used to be able to do pretty easy is now pretty hard for me to do… like carrying the co2 bottle up a 6’ ladder lol.

To refill my bottle it was $23 dollars and I would have to refill it about every 1.5 - 2 week’s to supply my 100ft2 room.

Because I didn’t have a mini split system and I was only “close” to being sealed off I felt like co2 was more valuable than gold.

I give co2 a run last year on 3 straight grows and just decided it wasn’t worth the cost especially when I had many successful harvest before that without co2.

Im not saying you can’t do it right either, I’m just saying I had a really hard time making it work for me because of my setup being an elevated room in my garage which is 20’ tall. If it was just a bedroom in my house then I know I could make co2 work really well but unfortunately my grow room is not a simple bedroom

@Hootie316 has done really well with co2. If he’s around here anymore maybe he can show you the bud that he showed me that he grew with co2, the bud was bigger than a chihuahua lol


Sorry to hear that brother , I didn’t know till now…
Stay strong and try to eat as healthy as possible… :+1::wink:


I second this.

If you were growing in a large room with ductless ac and a co2 burner, it would maybe be a discussion worth having. Not using bottles in a tent.

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Thanks guys, this reinforced what i was thinking.


Hello hello hello, these were my twins Buds
And of course I can’t show you because there is a large yellow sign blocking my view from Bergman. Hmmmmmm

I had to edit in order to send some. Lol
There were six shelves in all and 1.5 pounds each.


Hello hello hello, I see some administrative instructions and limitations were listed. Makes no sense when I was given a Badge that says this

What is the problem Hoot?