CO2 1000 cu ft room

Hello to everyone. I am looking to turn a 10x10x10 room into a closed growing enviroment. I have already installed a 12,000 BTU mini split a/c in the room. I want to run 6x315 CMH in there.

For co2 supplementation I am planning on buying a 0,75kw CO2 generator:https://www.greenspirit-hydroponics.com/hotbox-co2-generator-0-75kw. It can run on propane and on natural gas. My house has a natural gas supply that goes to that room as well. Other than that, considering co2 supplementation I would need a co2 controller and that's all? Do you believe temps would be ok with 6x315w CMH and this model of co2 burner?

I want to grow 12 plants in 15 gallon pots with organic soil. For dehumidifying I would use a 65 pint dehumidifier. How does my plan look? Thank you

weedlover_89 said:

Hello to everyone. I am looking to turn a 10x10x10 room into a closed growing enviroment. I have already installed a 12,000 BTU mini split a/c in the room. I want to run 6x315 CMH in there.

For co2 supplementation I am planning on buying a 0,75kw CO2 generator:https://www.greenspirit-hydroponics.com/hotbox-co2-generator-0-75kw. It can run on propane and on natural gas. My house has a natural gas supply that goes to that room as well. Other than that, considering co2 supplementation I would need a co2 controller and that's all? Do you believe temps would be ok with 6x315w CMH and this model of co2 burner?

I want to grow 12 plants in 15 gallon pots with organic soil. For dehumidifying I would use a 65 pint dehumidifier. How does my plan look? Thank you

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Sounds ok bud. I just ordered a trolmaster co2 generator. It’s has a built in controller. I ll get it in this week and let you know how it works. Good luck

Thank you for the reply, wishing you the same . Please let us know how it goes. I will do the same with my setup when I have it up and running. Some more questions that come to mind.

1)Should I have an active exhaust system turning on for a few minutes for every 2-3 hours? I was advised this would be the best, especially with a co2 burner. Could I have a succesful harvest without opening a hole in the wall of my room? That would be so convenient.

2)Considering control of humidity especially during the dark hours. The simplest approach would be to get a unit with its own % setting and just let it run day and night?

3)Supposing I don't open a hole in the wall for exhast, for the last two weeks of flowering I would be ok simply by adjusting to ~400 ppm of co2 and making my best to reduce RH to 45-50 for a trouble free harvest? And what about drying? Just dry under the same conditions with optimal temperatures? I wouldn't be able to dry my harvest in ambient temps of summer 95F air.

Any suggestions are more than welcome...

Your 65 pint dehumidifer might not be enough.

I have a smaller room (8x8x7ish), and I have to empty my 90 pint twice a day during the summer. And it barely keeps my humidity in check. In winter I have to run a humidifier.

I am in the midwest however. This might change depending on your locale.

Thanks for the heads up . Summer is dry in my locale, usually 30-40%. I could buy a 90 pint dehumidifier after all. The dehumidifier will be connected to sewer drainage and all water will be draining there so I won't have to empty it all the time. Same with my A/C, this has been done already. I got a sonoff in order to connect the humidifier as well in case I need it.

I would like to go by VPD "suggestions" so this would require to be able to regulate temps and RH as best as I can. Higher RH would be welcome until 2 weeks before harvest. I could get a second sonoff for the A/C or that wouldn't be nescessary? Models I found are suitable for up to 16A-240v.

Other than that, I still don't know if a hole in the wall would be appropriate given the fact that I will be running a burner, trying to avoid potential toxic concentrations of CO and such. Any growers out there who are running burners and haven't opened any holes for exhaust in their rooms? Trying to avoid it for many reasons.

weedlover_89 said:

Thank you for the reply, wishing you the same . Please let us know how it goes. I will do the same with my setup when I have it up and running. Some more questions that come to mind.

1)Should I have an active exhaust system turning on for a few minutes for every 2-3 hours? I was advised this would be the best, especially with a co2 burner. Could I have a succesful harvest without opening a hole in the wall of my room? That would be so convenient.

2)Considering control of humidity especially during the dark hours. The simplest approach would be to get a unit with its own % setting and just let it run day and night?

3)Supposing I don't open a hole in the wall for exhast, for the last two weeks of flowering I would be ok simply by adjusting to ~400 ppm of co2 and making my best to reduce RH to 45-50 for a trouble free harvest? And what about drying? Just dry under the same conditions with optimal temperatures? I wouldn't be able to dry my harvest in ambient temps of summer 95F air.

Any suggestions are more than welcome...

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I wouldn’t worry about an active exhaust system unless you have issues with plant health. I run my rooms totally sealed. At one location I had major issues with my co2 burners and had to turn them off and run unsealed. Everyplace is different. Definitely don’t wanna dry in high heat bud. I like to decrease humidity once the buds get good sized, usually start decreasing around weeks 5-6. Hope this helps!

eric2028 said:

I wouldn’t worry about an active exhaust system unless you have issues with plant health. I run my rooms totally sealed. At one location I had major issues with my co2 burners and had to turn them off and run unsealed. Everyplace is different. Definitely don’t wanna dry in high heat bud. I like to decrease humidity once the buds get good sized, usually start decreasing around weeks 5-6. Hope this helps!

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Poisoning the plants is what concerns me the most. I read some threads here in the forum that troubled me and pointed towards having a ventilation hole running a burner. Yes, I learned early in my growing years not to dry bud in high heat.... If you don't mind sharing could you please let me know which were these major issues you had with your burners?

Other than that I was wondering if I could add 2 of those:https://www.todogrowled.com/gb/hlg-quantum-boards/58-hlg-260w-quantum-board-kit.html

plus 1 DIY Cree CXB 3590B 350W along with the 6x315W CMH and not face problems with heat. That would be perfect and would cover most of the 10x10 room. If I decide to go only with the 6x315 I will have to use about 10x5 realistically to make CO2 efficient.

weedlover_89 said:

Poisoning the plants is what concerns me the most. I read some threads here in the forum that troubled me and pointed towards having a ventilation hole running a burner. Yes, I learned early in my growing years not to dry bud in high heat.... If you don't mind sharing could you please let me know which were these major issues you had with your burners?

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Co2 burners are made to create optimal conditions for plant health. I don’t think it’s common for them to cause issues. I had completely healthy plants go from unsealed veg rooms to 800 ppm bloom rooms that were sealed. Plant health declined rapidly. Droopy, yellowing leaves, and stopped drinking. This is across 4 separate rooms. Co2 lowered to 500 and not much different. Rooms unsealed and co2 turned off. Plant health improved over Afew weeks. 3 of 4 burners were brand new. The flames were tight and blue. That was a bad experience for sure.

weedlover_89 said:

Other than that I was wondering if I could add 2 of those:https://www.todogrowled.com/gb/hlg-quantum-boards/58-hlg-260w-quantum-board-kit.html

plus 1 DIY Cree CXB 3590B 350W along with the 6x315W CMH and not face problems with heat. That would be perfect and would cover most of the 10x10 room. If I decide to go only with the 6x315 I will have to use about 10x5 realistically to make CO2 efficient.

Click to expand...

I personally don’t have experience with those lights. You can get a ballpark idea of cooling requirements from watts x 4 btus=_
12,000 btus=1 ton(you probably know that). I wouldn’t over complicate things tho friend, keep it simple you can always add more later. Hope this helps.

I gave up on propane C02 generators. The off gassing of ethylene is what is causing harm to the plants. Go with bottles for the win.

Rule #1 - Shit happens.
Because of that, every sealed room needs an exhaust system with a carbon filter to scrub the air before it gets out (assuming outlaw conditions.)
Use an electric damper on the exhaust to keep things sealed when they are supposed to be. Have the plug for the exhaust fan on the same circuit as the damper so it only opens when exhaust is needed.

I have also had problems with propane CO2 burners. Moved to tanks and smooth sailing.


BTW, not sure how many plants you'll have in that room, or better, how much actual canopy you will have, but those 315s each cover 3ft x 3 ft area. 6 won't cover your 10x10. You need 3 more of them to cover that room, but with the 10 ft ceiling, I don't know why you wouldn't run four 1000 watt HID's instead.

eric2028 said:

Co2 burners are made to create optimal conditions for plant health. I don’t think it’s common for them to cause issues. I had completely healthy plants go from unsealed veg rooms to 800 ppm bloom rooms that were sealed. Plant health declined rapidly. Droopy, yellowing leaves, and stopped drinking. This is across 4 separate rooms. Co2 lowered to 500 and not much different. Rooms unsealed and co2 turned off. Plant health improved over Afew weeks. 3 of 4 burners were brand new. The flames were tight and blue. That was a bad experience for sure.

And you never knew why this happened? Bad experience for sure.Especially with the generator doing seemingly proper burning.

I personally don’t have experience with those lights. You can get a ballpark idea of cooling requirements from watts x 4 btus=_
12,000 btus=1 ton(you probably know that). I wouldn’t over complicate things tho friend, keep it simple you can always add more later. Hope this helps.

Click to expand...

And you never knew why this happened? Bad experience for sure.Especially with the generator doing seemingly proper burning

What seems to create confusion is the fact that "a watr is a watt" in terms of heat.So,400 watts of heat are the same whether using hps or Led,same amount of heat in a sealed room?Just wondering because the first converts ~30% of its energy to light,the second one ~55%.

QUOTE=digging;8550322]I gave up on propane C02 generators. The off gassing of ethylene is what is causing harm to the plants. Go with bottles for the win.[/QUOTE]

Finally decided to go with bottles after finding out I could refill them in my local growshop for 2,5$/kg!

Raho said:

Rule #1 - Shit happens.
Because of that, every sealed room needs an exhaust system with a carbon filter to scrub the air before it gets out (assuming outlaw conditions.)
Use an electric damper on the exhaust to keep things sealed when they are supposed to be. Have the plug for the exhaust fan on the same circuit as the damper so it only opens when exhaust is needed.

I have also had problems with propane CO2 burners. Moved to tanks and smooth sailing.


BTW, not sure how many plants you'll have in that room, or better, how much actual canopy you will have, but those 315s each cover 3ft x 3 ft area. 6 won't cover your 10x10. You need 3 more of them to cover that room, but with the 10 ft ceiling, I don't know why you wouldn't run four 1000 watt HID's instead.

Click to expand...

Decided to go with bottled co2 after all! Refilling was a problem in my mind, seems it is solved.

Not having an exhaust seems so convenient but I am working on implementing it in the growroom.Opening a 150mm hole minimum is not my best.I was advised by a knowledgeable friend that I should not exceed 500 ppm of Co2 if I can't vent at night.He said it would be better to simulate concentrations of unsealed room and just tweak temp/humidity according to VPD with lower temps.
He is not a fan of higher co2 dosages.Said that higher temps that must accompany them destroy terpenes.
Considering light, that's another reason I can't implement high co2 concentrations.Would need about 750w/m2 of hps light or 630w/m2 cmh to take advantage of the higher co2 , correct? My a/c cannot keep up with those amounts of energy.I have never used 1000w HPS.I have those CMH and Leds at hand,they are quality lights. Going to play with 6x315 CMH and 2x300w COB and 1x 300w Quantum Board Led.

weedlover_89 said:

And you never knew why this happened? Bad experience for sure.Especially with the generator doing seemingly proper burning

Never figured out the issue. Rooms stayed unsealed and are great still. The burner that was used functioned fine at a different location with no issues. Common denominator is gas issue at this location but who knows.

What seems to create confusion is the fact that "a watr is a watt" in terms of heat.So,400 watts of heat are the same whether using hps or Led,same amount of heat in a sealed room?Just wondering because the first converts ~30% of its energy to light,the second one ~55%.

Click to expand...

I ve found this to be a ballpark with hps and fluence led lights. For fluence they advise 3.56 btu per watt if my memory is right.

weedlover_89 said:

QUOTE=digging;8550322]I gave up on propane C02 generators. The off gassing of ethylene is what is causing harm to the plants. Go with bottles for the win.

Click to expand...

Finally decided to go with bottles after finding out I could refill them in my local growshop for 2,5$/kg!




Decided to go with bottled co2 after all! Refilling was a problem in my mind, seems it is solved.

Not having an exhaust seems so convenient but I am working on implementing it in the growroom.Opening a 150mm hole minimum is not my best.I was advised by a knowledgeable friend that I should not exceed 500 ppm of Co2 if I can't vent at night.He said it would be better to simulate concentrations of unsealed room and just tweak temp/humidity according to VPD with lower temps.
He is not a fan of higher co2 dosages.Said that higher temps that must accompany them destroy terpenes.
Considering light, that's another reason I can't implement high co2 concentrations.Would need about 750w/m2 of hps light or 630w/m2 cmh to take advantage of the higher co2 , correct? My a/c cannot keep up with those amounts of energy.I have never used 1000w HPS.I have those CMH and Leds at hand,they are quality lights. Going to play with 6x315 CMH and 2x300w COB and 1x 300w Quantum Board Led.[/QUOTE]

You can’t go wrong with bottled but it’s a commitment lol. Good luck bud!

Quotes were screwed up sorry

I think with bottles you are better off. The added heat and humidity would not have worked in your favour.

Is this a 1t mini split, window banger or a two hose household? Makes a big difference especially with summer around the corner.

One thing I see a lot of people do is build themselves into a corner. Fire up the room at operating conditions well before you plan to load plants if possible. You never know where the first fire to put out starts. Metaphorically but not always..

weedlover_89 said:

QUOTE=digging;8550322]I gave up on propane C02 generators. The off gassing of ethylene is what is causing harm to the plants. Go with bottles for the win.

Finally decided to go with bottles after finding out I could refill them in my local growshop for 2,5$/kg!
Decided to go with bottled co2 after all! Refilling was a problem in my mind, seems it is solved.

Not having an exhaust seems so convenient but I am working on implementing it in the growroom.Opening a 150mm hole minimum is not my best.I was advised by a knowledgeable friend that I should not exceed 500 ppm of Co2 if I can't vent at night.He said it would be better to simulate concentrations of unsealed room and just tweak temp/humidity according to VPD with lower temps.
He is not a fan of higher co2 dosages.Said that higher temps that must accompany them destroy terpenes.
Considering light, that's another reason I can't implement high co2 concentrations.Would need about 750w/m2 of hps light or 630w/m2 cmh to take advantage of the higher co2 , correct? My a/c cannot keep up with those amounts of energy.I have never used 1000w HPS.I have those CMH and Leds at hand,they are quality lights. Going to play with 6x315 CMH and 2x300w COB and 1x 300w Quantum Board Led.

Click to expand...

Commercial sealed grows don't vent at night and you don't need to either.

My room gets high levels of Co2 during lights out when I'm heating another area of the building with propane space heaters, I'm at 12-1300 sometimes and it has no bad effects on my plants, just use the bottle slower...

I have a 12" fan filter to vent with if my AC fails though and would love to have a controller and solenoid dampers to use it to scrub the room or switch to vent, basically it's a big expense for the fan and filter if it is only used in the event of AC failure.

eric2028 said:

I ve found this to be a ballpark with hps and fluence led lights. For fluence they advise 3.56 btu per watt if my memory is right.

Thanks for the info, good to know! Quantum Boards are supposed to be really efficient considering heat!

Click to expand...

You can’t go wrong with bottled but it’s a commitment lol. Good luck bud![/QUOTE]

Yeah, I already understood it's a commitment carrying 2x20 lb tanks to my place today, lol! Thank you bro, wishing you the best, I wish I have the chance to get you to try my goodies in the future for your good vibe!

Raho said:

Rule #1 - Shit happens.
Because of that, every sealed room needs an exhaust system with a carbon filter to scrub the air before it gets out (assuming outlaw conditions.)
Use an electric damper on the exhaust to keep things sealed when they are supposed to be. Have the plug for the exhaust fan on the same circuit as the damper so it only opens when exhaust is needed.

I have also had problems with propane CO2 burners. Moved to tanks and smooth sailing.


BTW, not sure how many plants you'll have in that room, or better, how much actual canopy you will have, but those 315s each cover 3ft x 3 ft area. 6 won't cover your 10x10. You need 3 more of them to cover that room, but with the 10 ft ceiling, I don't know why you wouldn't run four 1000 watt HID's instead.

Click to expand...

After much thought I am contemplating on opening a 150 mm hole with an exhaust fan at 500cfm for the 1000 cuft room. Perhaps I would do it in the window glass after all.

Mikell said:

I think with bottles you are better off. The added heat and humidity would not have worked in your favour.

Is this a 1t mini split, window banger or a two hose household? Makes a big difference especially with summer around the corner.

One thing I see a lot of people do is build themselves into a corner. Fire up the room at operating conditions well before you plan to load plants if possible. You never know where the first fire to put out starts. Metaphorically but not always..

Click to expand...

Thank for the heads up my friend. That is a 1t mini split. Would not put anything else besides a mini split, especially with hot summer approaching. I have tried everything in the past without a/c for indoor growing with no success. Luckily I was always growing with organic soil and quantity was not totally f*cked up,even with high heat. Of course I will make sure to test the room for 1 day without any plants in it. Just getting my feet wet, I have many parameters to take care of.

Chunkypigs said:

Commercial sealed grows don't vent at night and you don't need to either.

My room gets high levels of Co2 during lights out when I'm heating another area of the building with propane space heaters, I'm at 12-1300 sometimes and it has no bad effects on my plants, just use the bottle slower...

I have a 12" fan filter to vent with if my AC fails though and would love to have a controller and solenoid dampers to use it to scrub the room or switch to vent, basically it's a big expense for the fan and filter if it is only used in the event of AC failure.

Click to expand...

Exhaust fan could be a plan B in case co2 runs out, operating it for 15 minutes/hour or something like that, even with a/c on.And vent in any case at night. Anecdotally I have seen reports by growers mentioning it is a better practice than no venting. And my knowledgeable friend swears by it. He even said there would be no meaning in operating the system without any exaust at all for very high ppms, 1100-1500.

I am looking for research on terpenes creation and correlation with high temperatures during first weeks of flower. I know that our lovely plants boost the terpenes during the last 3 weeks, that's why in the 2 remaining weeks mark we halve co2 dosages and reduce temperatures among other things. Wondering how counterproductive in terms of quality higher temps with high PPMs of co2 (1000+) are before the last 3 weeks.

Other than that, contemplating on an auto watering system. I will have 12x15 gallons pots with organic soil and 8x6 gallon pots. Was looking into Autopots, putting 15 gallon pots into large trays with aqua valves (autopot accessory) and such via easy2grow kits. Don't know how well it would work, still searching...

And one more question, regarding the damper for the exhaust system in case I decide to install it. Does it have to be motorized? A simple backdraft damper connected inline with the fan wouldn't do? For example for my TD 800/200 fan there is a suitable damper: Would this be ok or I would have to run a motorized damper? Thanks for all the help guys!

when your plants are small they don't consume much CO2. You will find that just you working in the room and exhaling CO2 can raise the level above the ability of the plants to handle it. Just an example of an unexpected CO2 issue you will probably have to deal with at some point where having a carbon filtered exhaust will be very nice.


You have a secret 1000 cu ft room, not a legal licensed warehouse. Behavior/strategies will be different for those 2 situations. Sounds like you are adding the equivalent watts in other lights (LEDs) to handle where the 315s come up short. Should be fine.