Everything Co2

I wanted to do an experiment with Co2 to see how much of it plants actually consume. I realized I didn’t have the equipment to run control tents so I decided to come at it from a different angle. I have the room that my grow tents and Grobo all live in, spare bedroom 12’ x 12’ room. With me home a lot and my gf working from home with the dog running around the entire condo stays at a pretty consistent Co2 level of 1,000-1,100 ppm which is supposed to be “close to perfect” levels for cannabis (please correct me if what I read is wrong, I take no offense). We all need to remember that any animal is a Co2 factory and that includes us.

So for my test I simply put a sensor inside the tent and a sensor outside the tent to see how much of the Co2 is being consumed by the plants. So my plants are in week 3 of flower so I figured this was a good time to pull off this test. I did the test for only a few days but the results were consistent each day. This is not a perfect test but I think you will find the results interesting. So what do you think happened?

The outside sensor read a consistent Co2 level between 994 and 1,044 ppm the entire 3 days of the test. My sensor tracks the highs and lows each day so this was easy to determine. The sensor on the inside of the tent on the other hand was not as consistent. During the day the levels would range from 430 to 685 ppm. This means the plants are consuming a pretty constant supply of about 500 ppm or 50% of the Co2 in the tent. I find this intriguing and I also had another interesting find. I read that plants don’t consume Co2 at night but while at night the Co2 levels did rise to almost 900 ppm showing an obvious consumption drop off but it never came up to the outside sensor reading. This showed me that the comments that plants don’t consume Co2 at night to be potentially debunked but more real science needs to be done.

I realize this is rough science but I did move the sensor in the tent all around to find the most consistent reading and it ended up being tied to the scrog in the middle of the tent right at the base of the flowers. This was a fun little experiment and I want to boost the Co2 level in the tent so I will be playing around to see the effectiveness of Exhale Bags and other Co2 supplements. Grow on my friends!


Cool test. Look forward to hearing more.
I understand co2 intake is directly linked to heat and i suspect at night when heat substantially lowers this is part of the reason and part it switches to different functions at night as well.
Good to know!


I have done many experiments with Co2 to date… And I can tell you it is the hardest perimeter to efficient control… Everything else super easy…

If you want to take full advantage of Co2 you need some powerful lighting… (without this Co2 will not do much for you)

I was pushing 2 630 Watt LED in my tent running temps 85 to 90… I pushed the plants with 1200 Par / ppfd. I found this to be a bit on the strong side 1100 seemed better… I’m not sure how much info you want here but fell free to ask me any questions on Co2.

If I was in your shoes and my house is 1000 to 1100 ppm I would put a control in place when Co2 drops to say 900ppm turn on a intake fan to increase your co2 level back to 1000 to 1100… (take air from house )

You are correct plants don’t Photosynthesize without light so no co2 is absorbed by the plant with the lights are off…

I never had luck with Exhale Bags… You want to play the co2 game only 2 ways (my opinion) get you self a co2 regulator and tank… Or a Co2 generator both ways have there advantages and disadvantages

Generally speaking here are the correct light levels for each stage:

• Seedlings or clones which are newly sprouted or planted: 100 umols/ms PPFD +/- 20
• Rooted clones/young veg plants: 250 umols/ms PPFD +/- 50
• Vigorous veg plants: 350 umols/ms PPFD +/- 50
• Vigorous veg plants:(supplemental CO2 of 1200ppm+) 550 umols/ms PPFD +/- 50
• Reproductive/flowering plants (not using supplemental CO2): 750 umols/ms PPFD +/- 100
• Reproductive/flowering plants (supplemental CO2 of 1200ppm+): 1000 umols/ms +/1 100

One more thing to add alot of people think to only use co2 in Flower but done correctly in Veg you can build a rock star plant


@Mpower11 great feedback brother! Really appreciate the insight. I am just playing around right now and want to grow better weed than my buddy who had been doing it for 20 years and thinks he knows everything. I know from my research that he is old school and doesn’t know much about all of the advancements in the last 10 years so I hope to be putting him to shame real soon. So far my bud has been on par with his and I have 1 year of experience. He seems to think that with his experience, I don’t have a chance but I am confident that I will surpass his quality very soon. Was hoping Co2 may give me the edge since he doesn’t use it.


I’m locked and loaded!!!

Question can you control your climate 90% on target all day and Night long?


Wow, look at that set up! I hope I can get myself that organized some day. I have my current set up on autopilot so whenever that happens I need to think up a way to challenge things, not sure why I can’t just be happy with what I have. :upside_down_face:


Have you seen the Cannatrol Cold Cure Boxes? I have one now and am in love. My buddy is now getting one too unfortunately because I thought it was going to help me beat his quality.


Oh yea man his setup is boss for real :flushed: I love looking at his stuff just reminds where I’m trying to get to :+1:t2::dash::seedling:


I know why because you know better Is possible and you enjoy growing. I lost track how many times I have purchased and repurchase hardware to make improvements. My hope is if you go down this path I can save you time and money.

You can and will outgrow your buddy if you want to. But I will be honest with you I think your going about it wrong. Co2 does work well if used correctly. If you just blindly inject Co2 into your grow space your not going to get the gains your hoping for vs the cost. Now if my house was around 1000ppm hell ya I would have fans exchanging the air in my grow space ASAP for free why not.

Back to the point master VPD. Don’t just say I’m in Veg so 40 to 60 perfect is good. You want to get to the next level master environment first. A prefect climate will out preform a poorly executed Co2 grow everytime. I recommend not to play with Co2 unless you have full control of your Environment first (Master VPD) that add Co2

If you to out grow your buddy that is your weapon I believe. Training is very important also but I believe you have that part under control already.

Something to think about also that a lot of people don’t think about is genetics super massive roll. You have a shit plant (genetic) you cannot fix that with Co2 or VPD.

I sow 2 to 3 times the plants I want and only keep the best why?? I have no plans on wasting 4 plus months of my life on genetics I don’t like.

Let me know your thoughts. And I will help you in any direction you want to go.

I really love everything about that machine but I due have a couple concerns.

1). I’m worried about it being to small for the price
2). What happens if you have 2 grows at different drying stages?
3) I spend a lot of time setting up my automatic burping jars system. And honestly it works like kick ass good. I can setup auto jars at different stages with really no limit for space. You can see it here

But I have to be honest I do have the itch buy one. :scream:


I’m on that train :mountain_railway: for saving time :alarm_clock: an money :yen: just letting this current situation play it self out an I’m on board :+1:t2::dash::seedling:


@Mpower11 You definitely sound like you understand the correct path so I will listen. I am still a novice but want to keep learning, it’s like crack to me! Every time I learn something new it makes me so excited, like a little kid.

I need to polish my growing skills before I add the Co2 variable because I don’t want to do it if I can’t do it right. My next tent will be active soon so I will have a place to experiment with any new toy or technique that comes along.

I agree with you 100% on genetics. My attitude to save underperforming plants is leaving me. My buddy has told me from the start, “weak seedlings will produce weak bud, don’t waste your time.” I of course didn’t listen and have spent wayyyyyy to much time trying to save plants that I should have just pulled out and started over.

Cannatrol Cure Box

  1. It may be too small for you but 2.2 lbs of wet bud is it’s max and I don’t have a tent that yields even close to that so fine by me.
  2. It’s true, one can be in cycle at a time, would need multiple units to do this. If you have the funds I recommend getting 2 anyways. It can store 4 lbs of dry so it can save you a lot of mason jar opening and closing. People keep their past grows in labeled paper bags in the unit and just pull out when they need it. Can hold bud for over up to a year I believe.
  3. You already have your auto burping system so you don’t really have as big of a need but don’t forget about the temperature control. I can contest that the unit keeps perfect temp and dew point.

Your help is always appreciated!


This is the correct path forsure

I’m telling you Co2 is tough animal because once you have high powered lighting to take advantage of Co2 now you made a heat problem… If you turn on exhaust fans you then lose all your Co2… So you end of needing AC or find a balance between heat and loss of Co2…

Let’s get down to business what equipment do you have? What are we working with? How do you want to approach the project?

You buddy isn’t wrong you start with a weak plant you end the same way… Now If your months into the grow and you run into a problem I get it… Try to save the plants… But if you just sowed or a few weeks into the grow I would start over 100% or just grow extra plants and pick the best…

Don’t speak to fast with 4 plants in a tent you can pull in that kind of weight np at all…

With my auto burping jars and adding Boveda 62 % packs… I never have to open my jars but the cannatrol box is on my radar for sure. I also recommend you take XX amount of your best buds and storage them correctly for 8 months… Around this time frame your bud is at it’s best… It’s like fine wine better with age…


Lol :joy: the funny thing is he got me looking :eyes: at plants :seedling: the same way agreed on everything u said he is a really gd teacher :man_teacher: an plan on learning a whole lot more with his great :+1:t2: advice :+1:t2::dash::seedling:


I am just about to have my second tent set up. I was unemployed due to Covid but I have a new job that is getting in the way of my growing :joy::joy:. I am the new guy and have to prove myself all over with a new company, hate this part. Off to a good start already so hopefully I will have some more time soon to put back into growing. My set up is in flower and is automated with heat, ac, humidity so just watering every 2-3 days watching the buds stack up nicely.

Once I come up for air I will definitely reach out for pointers. Thanks again! :+1:t2:


Totally understand…

Do you understand VPD? Can you stay on target all day and night?

When your ready let me know if you need a hand!! Cheers

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I don’t understand it but I do follow that same chart. :rofl:


For now I would just following. Lol

But this examples it well if your in sponge mode.

Temperature and How It Relates to Humidity

Temperature and relative humidity are closely related to each other.

[Temperature and Humidity Monitor - Digital - Available from Amazon.com

Relative humidity is measuring how much water is “being held” in the air compared to the maximum amount of water that can be held at that temperature.]

[Warm air can “hold onto” more water than cool air. Plants will tend to thrive at different relative humidities depending on the temperature of the air. Once the air becomes too saturated with water, it will tend to form dew or films of water over leaves, which leads to mold.](
[For those interested in learning more about the science behind this, there is a term used by greenhouse growers known at VPD, or Vapour Pressure Deficit, that roughly measures the temperature and relative humidity.](

[According to ]Wikipedia: “the ideal range for VPD in a greenhouse is from 0.45 kPa to 1.25 kPa, ideally sitting at around 0.85 kPa. As a general rule, most plants grow well at VPDs of between 0.8 to 0.95 kPa.”

When growing plants, temperature is just as important as the Relative Humidity (RH) of the air, if not even more so! You need to control both temperature and RH at the same time to get the best results when growing cannabis.

  • If the air is too hot and dry (high VPD), plants will tend to have stretched growth.
  • If the air is too cool and humid (low VPD), plants are more prone to problems with mold or fungus.

Here’s what that means to you, the grower:

Cannabis likes a comfortable room temperature, or a little warmer – not too dry, not too humid. For most growers, that is all you need to worry about.

If your grow room feels warm or cold, humid or dry, that is a sign that you may want to look into changing the temperature and/or humidity of your grow area.

Generally, cannabis plants prefer temperatures in the 70-80 °F (21-27 °C) range during the day when lights are on. When lights are off (or at night), cannabis plants are happy with slightly cooler temps.

What if it gets too cold?

Colder temps will tend to slow down growth. Temps lower than 60°F (15°C) can upset plant growth and freezing temperatures will shock or even kill a cannabis plant.

Can cannabis stand higher temps? What if my grow room is too hot?

Please note that too-high temps in the flowering stage will not only slow down bud growth and cause fluffier buds, but it will also tend to reduce the potency of your buds by causing some terpenes and cannabinoids to burn off. Keeping the grow room temperature under control is important in the flowering stage!

Advanced Tips

  • With bright grow lights (such as 600W HPS and larger), cannabis plants can thrive at temps up to 85°F (30°C) even with no CO2 enrichment, as long as there is low relative humidity and plenty of air movement.
  • Cannabis plants can thrive at higher temperatures, up to an ultimate max of about 95°F (35°C), in an environment with low humidity, extremely bright grow lights and enriched CO2 (above 1500 PPM) – this is not your average grow!
  • Cannabis prefers slightly cooler temperature at night (warmer night temperatures will tend to slow down growth – so you can use this knowledge and raise night temperatures to slow down stretching plants that are growing too tall too quickly)

Thanks Mark! You da man


It definitely takes time to dial it in. I use a pulse monitor in my tent which give u live time parameters. U tell it what u want your target VPD and it will give u settings. Definitely need full automation with temp and humidity. Next grow I plan on CO2 enrichment which is gonna have a learning curve of its own.


All I can say is it’s a addicting love hate relationship…