New sealed room c02 and ac many questions please help

Hi my fellow growers, I have moved from tents and a negative airpressure in a lung room for years back into a dedicated open room again.

I decided its time to try and push things to the next level. I have managed to constantly yeild 300-350g per m2(10.7ft2) dry nugs no bottoms or sugar included. With 3-4 week veg and 7 week flower so really fast turn around. I used a mixture of 720w bar leds and 600w digital hps in coco mix perlite ect. Hand water 1500 ppm low 6s ph. In 3 gal pots a bit less than half gallons waterings

Now i have decided to get rid of my tents and go sealed room for full climate control and add 2 minisplit ac units for redundancy so its 2.5ton together.

Room is 13ftx20 and 7ft 11inch high
I have a massive co2 tank and regulator and controller hooked up.
Im running the room at 84f-88f lights on with 60-70%rh chasing vpd and 78.8f-81f lights off.
I run 3 x 60pint dehumidifiers on different locations 2ft off the ground ontop of a black storage tub. (i know i need Way more then that but funds are limited for now its eating power lol)
C02 running at 1000-1300ppm (i have read so many mixed opinions on what to run) and i have set mine lower today now running 650ppm-1050ppm
Running 1000-1200 ppfd light from mostly 720w bar leds mixed with a 600w hps here and there.

I have did the whole conversion to a sealed environment in week 1-2 of flower that wasn't to ideal. So im new to a sealed room i have many questions.
I have tried to give as much information as possible obviously there is always more i could try and give but i only have so much time. I have 64 3 gals running now with 4 720s and 2 600w hps week 3 of 12/12 for reference.

So my questions are:
1: I have 2x 8inch pipes from the rooms roof that i used to use for a negative pressure so i dumped all the hot air out and let the cold air come im without a fan on the other pipe. Since its probably 7+ foot high on the roof will co2 leak out of it if i leave it open but negative pressure fan off and inlet side open? Since c02 is 50% more heavy then air in theory without a fan pulling air out will i lose major co2? The reason im asking is ive heard its good to vent your air out for 30mins or so on lights off to get rid of unwanted gasses? and for c02 levels to be ambient and not super high during lights off. Opinions? Ive heard many mixed ones... But id love to hear more.

2: C02 levels during veg and pre flower and mid to late flower.

3: feeding ppm in veg, flower ect with Co2. Added Silica? Calmag?

4: i want to run 6-8 720w lights and either do 100 girls in 3gals or cut it down to say 26-36 in 6.75gal buckets? Obviously longer veg what size dehumidifier do I really need some people say you need to size it for the room and others say for the amount of water you give/want to remove from the room. Im considering a 190 pint industrial dehumidifier to replace the 3 mini units but i might need more then just that?

I'll leave it at that for now
Thanks for your time and input it is really appreciated!

Damn, all sorts of people reading but no one replied?

Well, I'm jealous 'cause I'm in a 2' x 4' tent in ambient CO2. I do end up at with good yields (abut 700gm/sqaure meter) but the main reason is that I give my plants a lot of light.

Zero hands on experience with enhanced CO2 but Bugbee recommends 1200 and 1200. I think I've read that CO2 levels don't matter during lights out but I have to wonder about that because stomata are used to take in CO2 but also are used for transpiration.

Different CO2 levels in veg vs flower? Just asked Grok and, yes. More importantly, Grok explain why to change them.

Temps are a big deal with CO2, You can run up to 85° in veg which really boost production. The information in this video is very valuable because most research is done using CO2 so it applies directly to your environment.


The light saturation point for cannabis in ambient CO2 is 800-1000µmol, assuming that light is the limiting factor, and that's strain dependent. Apparently, indicas max out at the 800± mark, while sativas can take advantage of 1k. I routinely grow at 1k in ambient and, seeing that elevated CO2 gives a 30% to 40% increase in yield (depending on whose research you read), I'd look to run at 1200-1500. The rationale for that is simple—crop mass and quality increase directly as light levels increase. Given the opportunity to run CO2, there's no question that my PPFD's would be in the 1500 range, assuming that the plants were thriving at that level, of course.

In that past week or so, I've spent a fair amount of time with chatGPT and Grok. In both cases, I've fed them info about my grow setup and growing processes and have come up with solid recommendations about how to improve my growing processes. After, perhaps, 8 hours of working with them, I will continue to use them.

Re. silica—I always use silicon in my grows. One of the things that Grok recommended was to use it up until the 3rd week in flower because, after that, it might inhibit cell expansion in the buds. Bugbee recommends it (and provides the basis for his recommendation) so I continue to use it. It strengthens cells which acts to strengthen branches and also makes the plant more resistant to disease and infestations.

Re. CalMag - companies sell fertilizers that provide macro and micro nutrients in certain proportions. There is no magic about the ranges of proportions of the chemicals that cannabis uses and, as long as those chemicals are provided in a certain range of concentrations, cannabis will grow well.

Adding a fertilizer, whether it's a "bloom booster" or "CalMag" will tend to change those proportions. Growers seem to see CalMag as a supplement but it's just another bottle of chemicals. If it's not a component of the line of ferts you're using, I wouldn't use it. I have a bottle of CalMag. I bought it when I started growing four years ago and the only use I have a for it is to pour a little bit of it in my RO water so that I can test the pH of the RO.

Re. EC—one suggestion that Grok or chatGPT made was that I increase my EC levels. I've been at 0.8 in seedling and early veg, 1.2/1.4 in veg, and then 1.8 in flower, dropping again in late flower. Both AI bots advised me that higher EC levels would support the higher growth rates that I get from running at 1kµmol. The bot (I don't recall which one) asked me for dimensions of the buds from my last grow along with the weight. the response was that my bud density would increase by increasing EC in flower and by not dropping EC in late flower.

420bongs said:

1: I have 2x 8inch pipes from the rooms roof that i used to use for a negative pressure so i dumped all the hot air out and let the cold air come im without a fan on the other pipe. Since its probably 7+ foot high on the roof will co2 leak out of it if i leave it open but negative pressure fan off and inlet side open? Since c02 is 50% more heavy then air in theory without a fan pulling air out will i lose major co2? The reason im asking is ive heard its good to vent your air out for 30mins or so on lights off to get rid of unwanted gasses? and for c02 levels to be ambient and not super high during lights off. Opinions? Ive heard many mixed ones... But id love to hear more.

2: C02 levels during veg and pre flower and mid to late flower.

3: feeding ppm in veg, flower ect with Co2. Added Silica? Calmag?

4: i want to run 6-8 720w lights and either do 100 girls in 3gals or cut it down to say 26-36 in 6.75gal buckets? Obviously longer veg what size dehumidifier do I really need some people say you need to size it for the room and others say for the amount of water you give/want to remove from the room. Im considering a 190 pint industrial dehumidifier to replace the 3 mini units but i might need more then just that?

Click to expand...

1: Yes you will lose co2, co2 is 50% more heavy than air but co2 also mixes with air, co2 doesnt sink like everyone like the think, it mixes. Take blue dye that is 50% heavier than water and dump it in a glass of water, it mixes up and thats it, let it sit for 10 years its still mixed up..

2: 1500ppm, late flower you can cut it back to 800-600

3: 3.0EC. Should be using silica and make sure you have enough Ca and Mg, so it really depends on your nutrient line if you need a specific Camag product.

4: 100 plants under 8 lights in 3 gallons is dumb. What a waste of coco. 1 gallon tops per plant. dehumidification should depends on how many lights, 8 lights should have a Quest 205.

Delps8 said:

Damn, all sorts of people reading but no one replied?

Well, I'm jealous 'cause I'm in a 2' x 4' tent in ambient CO2. I do end up at with good yields (abut 700gm/sqaure meter) but the main reason is that I give my plants a lot of light.

Zero hands on experience with enhanced CO2 but Bugbee recommends 1200 and 1200. I think I've read that CO2 levels don't matter during lights out but I have to wonder about that because stomata are used to take in CO2 but also are used for transpiration.

Different CO2 levels in veg vs flower? Just asked Grok and, yes. More importantly, Grok explain why to change them.

Temps are a big deal with CO2, You can run up to 85° in veg which really boost production. The information in this video is very valuable because most research is done using CO2 so it applies directly to your environment.

The light saturation point for cannabis in ambient CO2 is 800-1000µmol, assuming that light is the limiting factor, and that's strain dependent. Apparently, indicas max out at the 800± mark, while sativas can take advantage of 1k. I routinely grow at 1k in ambient and, seeing that elevated CO2 gives a 30% to 40% increase in yield (depending on whose research you read), I'd look to run at 1200-1500. The rationale for that is simple—crop mass and quality increase directly as light levels increase. Given the opportunity to run CO2, there's no question that my PPFD's would be in the 1500 range, assuming that the plants were thriving at that level, of course.

In that past week or so, I've spent a fair amount of time with chatGPT and Grok. In both cases, I've fed them info about my grow setup and growing processes and have come up with solid recommendations about how to improve my growing processes. After, perhaps, 8 hours of working with them, I will continue to use them.

Re. silica—I always use silicon in my grows. One of the things that Grok recommended was to use it up until the 3rd week in flower because, after that, it might inhibit cell expansion in the buds. Bugbee recommends it (and provides the basis for his recommendation) so I continue to use it. It strengthens cells which acts to strengthen branches and also makes the plant more resistant to disease and infestations.

Re. CalMag - companies sell fertilizers that provide macro and micro nutrients in certain proportions. There is no magic about the ranges of proportions of the chemicals that cannabis uses and, as long as those chemicals are provided in a certain range of concentrations, cannabis will grow well.

Adding a fertilizer, whether it's a "bloom booster" or "CalMag" will tend to change those proportions. Growers seem to see CalMag as a supplement but it's just another bottle of chemicals. If it's not a component of the line of ferts you're using, I wouldn't use it. I have a bottle of CalMag. I bought it when I started growing four years ago and the only use I have a for it is to pour a little bit of it in my RO water so that I can test the pH of the RO.

Re. EC—one suggestion that Grok or chatGPT made was that I increase my EC levels. I've been at 0.8 in seedling and early veg, 1.2/1.4 in veg, and then 1.8 in flower, dropping again in late flower. Both AI bots advised me that higher EC levels would support the higher growth rates that I get from running at 1kµmol. The bot (I don't recall which one) asked me for dimensions of the buds from my last grow along with the weight. the response was that my bud density would increase by increasing EC in flower and by not dropping EC in late flower.

Click to expand...

Thanks so much for your reply. I was starting to think i should just remove the post when i saw no replys in 24h lol.

Wow 700 dry no suger or bottoms in that weight? per m2? Must be coke can size buds what strain? Total time veg + flower?

Good idea to ask chatgpt some questions i just find that i always take it with a pinch of salt. But it will definitely be 90% accurate.

I run my lights about 15-17 inches abive the canopy and get a reading of anything from 1000-1300ppfd maybe i should drop them closer because i have a mini split? Ive seen some vids of nice grows where the colas are like 2 inches from the light (id be scared of light bleaching but that didn't happen)

Ive never seen more contradicting information on this site than with c02 supplementation. It must be due to allot of people that comment have never really used it but want to say something. And don't mention the fact that they have not even used it. and that really caused allot of flase/bad information to be repeated out there.

I did use silica and calmag during late veg and pre flower

I run a Ec of 2-3 in flower depding on the stage and that was without c02 and the results were great. Now i need to figure this whole new setup out quickly...

nxsov180db said:

1: Yes you will lose co2, co2 is 50% more heavy than air but co2 also mixes with air, co2 doesnt sink like everyone like the think, it mixes. Take blue dye that is 50% heavier than water and dump it in a glass of water, it mixes up and thats it, let it sit for 10 years its still mixed up..

2: 1500ppm, late flower you can cut it back to 800-600

3: 3.0EC. Should be using silica and make sure you have enough Ca and Mg, so it really depends on your nutrient line if you need a specific Camag product.

4: 100 plants under 8 lights in 3 gallons is dumb. What a waste of coco. 1 gallon tops per plant. dehumidification should depends on how many lights, 8 lights should have a Quest 205.

Click to expand...

Good point man and my meter is about 5ft in the air and the reading is almost the same as at say 3ft. I need to get a ducting back draft damper today do you rate i put it on the intake and exhaust or will one side stop the "draft"?

Cool what would you say late flower is last 2 weeks? Or less? I find i have the best swelling from week 4-6+ and i cut at 7 maybe a bit early but i like it that way and the strain flowers fast.

Cool ive been using a 3 ec without co2 in the past and the leaf tips dont show any sighna of yellowing. so i should just leave it there? Or you rate it will take more? I use greenhouse feeding short flower powder feeding. NPK 16-6-26.
3.3% mg but no added calcium.

More roots more fruits is what i believe in and mostly because i hand water it gives me a 24h time to come back and water. Although i am in the process of converting to drippers and dosing the plant 4-5 times in the lights on stage then can i can try 1 gallon pots thanks for the advice i appreciate it.

The biggest question i have and the most conflicting information i get online is to vent or not to vent....

I have a friend that has a massive commercial grow and they say vent...
Ethylene gas buildup is not good. But not only that plants use oxygen.

Ai said,
"No, a closed CO2 environment is not ideal for plants, and they will not be able to produce enough oxygen for themselves. While plants do produce oxygen during photosynthesis, they also respire, consuming oxygen, especially at night. In a closed environment, the oxygen produced during the day would be offset by the oxygen consumed at night, potentially leading to a net oxygen depletion. Additionally, the build-up of CO2 can be detrimental to plant health and growth"

And i closed up my inlet and outlet permanently for the last week and it definitely doesn't look better than running without co2 so im really trying to cut threw all the myths quickly. Some of the pistols look damaged i suspect its a lack of oxygen or a buildup of gases or both.

I appreciate your input

should be hitting 1.5lbs to 2lbs per light without trying with co2. co2 is also cheap might as well set your low point to 1500 ppm and the high point at 1600 ppm that way it never dips below 1500.

xox said:

should be hitting 1.5lbs to 2lbs per light without trying with co2. co2 is also cheap might as well set your low point to 1500 ppm and the high point at 1600 ppm that way it never dips below 1500.

Click to expand...

I can definitely do that if I veg it longer or change strain. People love posting about gram per light or watt but nothing about veg time or flower time... Time is the most important factor its the only thing you can't buy or change. I get 7.4-8 rotations a year per tent on the cycle i was running (separate pre veg) which is allot more then most. That factor plays a big roll where others are doing 5 or less per year so just food for thought.
Thanks for the input.