I know… so that’s what we’re trying to figure out… what is actually damaging and detrimental to a plant
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Iv often read not to use co2 in veg
It’s even stated in this thread
Environment is everything so I think all other major points need to be checked off the list before adding o2
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@ReikoX is the man. I’m like @Papalag on the veg thing. You need some. Like Reiko said in a sealed room is a big deal. I don’t add any but from out side. It scared me once.( I had a bottle get away from me perforated my skin)(fked me up almost killed me) But better than putting oil in a oxygen regulator. Don’t ever put any oil in those things. Always read where the old timers would put a camping lantern in the area. I know they would do that if the lights went out.
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That stuff you see in movies with those high pressure bottles it can happen. I was trying to be slick and roll it with my foot didn’t have the top on the bottle and open the valve. I have done that many times before never had a problem. That bottle almost killed me. Took off like a rocket.
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I’ve seen that in veg though that lower like in 800s is still ok … but no point to go to 1500 until about a week into flower
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The effects of excess co2 on plants is incredibly species dependant, and we’re unfortunately wildly behind on cannabis specific scientific studies due to obvious reasons. You aren’t going to find a specific ppm where major detriment happens, because we’ve already figured out that 1200-1500 is the maximum (stage dependant) that we see benefits, so outside of a scientific study there isn’t any good reason to go above that right? We also just simply can’t fully understand what internal effects are happening until cannabis specific studies are done.
As for harm its doing, based on studies of other c3 plants (the photosynthesis type of cannabis) we can reasonably assume that a few things are at play. Excess co2 causes stomata to open less, resulting in decreased transpiration. This will affect their ability to manage heat and reduce water uptake, which will both reduce nutrient uptake and leave excess moisture in the medium which obviously isn’t necessarily ideal for root health in potted plants. We also know that excess co2 causes leaves to thicken, and that affects basic plant functions (photosynthesis, respiration, etc), but I can’t even pretend to fully understand or explain what actual effects that has. What ppm will these things happen in cannabis? No idea.
Most studies on this are done with food crops, and though excess co2 causes increased yield in many of the tested crops, it also reduces nutrient production to a notable degree. How does this translate to cannabis? Fuck if I know, I just search shit I don’t fully understand and pretend I’m not a dummy 
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So is the 10% gain due to thicker sugar leafs etc so with co2 there’s just more thicker plant material ie illusion : )
The thicker leafs will that reduce light penitration also and why an increase in lighting intensity needed : )
I’ll stick with fresh air
It’s in abundance , easy to get and free plus plants love it : )
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Perhaps some of it is, but the majority of it has to do with the RuBisCo enzyme having an affinity for both CO2 and O2. When it reacts with CO2 it produces organic compounds used in photosynthesis. More CO2 increases the chance that RuBisCo will bind with CO2 instead of O2. This increases photosynthesis, which increases the amount of light the plant can process.
As far as too much CO2, the plant does need the organic compounds produced when RuBisCo reacts with O2 for other processes. What that actual limit is for cannabis is unknown.
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Agreed… speculation without real results is NOT a real test… remember @ifish … my co2 levels are naturally always above 800 to 900… no costs… that’s free… my valves are off on my co2 so I am just going to be a high co2 grower… at least double the co2 as the rest of people who use 400 ppm air (normal fresh air) I think too much I veg causes the stomata to stay open etc… if avoided high levels during veg that wont happen I think… not know… think… I read it somewhere I cant remember …but I’ll say this… in veg I’d think 800 ppm is okay and allowing the o2 to have its main function in the plant as well as co2… but again no document that I can show because I read this all months ago… I’ll have to look again and see … 1 thing I know… I have never seen a co2 user revert back to not using co2… maybe adjust… but never toss aside
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Definitely a bonus been running a sealed room with a c02 burner for years . Bottles are a hassle especially when it’s time to refill .
In the long run a burner is the cheaper less hassle way to go . Only down side it does increase the room temps quite a bit till it reaches the set limit.
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I have 2 - 20 pounders and the co2 regulator… plus meters to tell ppms… I bought it all thinking I’d need it alot… not so much lol… only winter time using a open window to cool basement will it be used… and that’s if I happen to be in flowering 
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Also I believe that 10 percent gain is bud yield alone … I could be wrong but I doubt it on that
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I agree you can also push the plants a lot harder more nutes higher temps .
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You can also grow mushrooms in the same room, they shed CO2 as well.
Way more fun than getting a tank.
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I had my room sealed with co2 in a basement and I found my energy consumption was higher with an AC and dehumidifier running. Swapped out that AC and started pulling in fresh air and had some great harvests with less power usage. I was still using the tanks in the winter as heat and humidity were well managed and didnt pull in that much fresh air. I have a grow going this summer and the intake is on a lot so I left the tanks empty and the nugs are still nice and compact, actually I am starting to think thats more of a genetic quality than anything. Long story short I think I am going to sell off my tanks its just one other thing to deal with and im not convinced it has that much of a benefit for me personally. I have enough herb so the 10% isnt worth the time and money and the whole bringing tanks in and out of the house and the guys at the welding supply always asking questions about what im doing with the co2. If I could go back and start all over I would keep things so simple and just focus on environment and soil health.
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That sounds like great advice. I need toby a quality co2 meter I also grow in a basement and I feel like the CO2 probably higher than normal. Early 1950s therea gas furnace gas water heater. So I maybe already on the high side of normal.thanks I think I’m going to keep it simple
You could get those big fungus blocks at one time. I’m probably sure you still can.
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I would say in a sealed room you will need to add CO2 if you do not have fresh air coming in from outside. It is a must. If you’re in a house and you’re grown in one room and the door is open pretty regular during the day I would not worry about it. With me all I do is open the vent on my air conditioner. It does leak smells. It is what it is.
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Yeah I think I’m going to just seal everything up best I can except for the exhaust and intake vents and maybe on the future I can cover those ports. Thank you for the advice. I will have a small lung room that does have a air duct running to a bedroom I could possibly add a vent
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Ive seed yield increase from 10-15% if not even more. The buds swell more and they feel alot more dense. The thc levels remain the same. My levels where around 1500-1600 and It was not a sealed room. This was my main flowering room and I also had multiple tents at another location without CO2 and so i did many experiments with different setup with and without CO2 to find what worked best for me. My conclution was CO2 with 6000w full spec leds with rdwc system and ph buffering nutes, organic water filter with added bacteria culture gave the absolute highest yields. Ive tried every light/grow system on the market. Also without CO2 i found that Organic soil grow gave the highest yields, but it was finicky when you got around 100 plants flowering at the same time. So i tried to get it to work with auto watering systems. But they never really got the same results as hand watering.
When i reflect on it some more, i wouldnt say that CO2 is for home growers. Its more of something for commercial grows where the 10-15% extra is tied to money. Its probably cheaper and easier to get a extra small tent to get that extra 10%. When most home growers pull 100-500g of dry bud that extra 10% is quite small compared to what i means to run everything correct. I mean when you pull 15-20 kg that 10% is over 1kg extra of buds.
Just some thoughts of mine.
Pz my growmies 
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