How much CO2 do plants put out while they sleep???

This is the first run I divided up an enclosed room and swapped out plants between 12/12 shifts in the same room. Normal co2 ppms in my house are 550 - 800. I'm finding PPMs in the grow room running 1000 - < 1300 ppm most of the time... is it possible the co2 is coming from the sleeping plants? I remember hearing something about them putting it out during night shift... or should I look for another source?

how are you measuring, because 550- 800 ppms is really high for just average with no supplement. 3-400 is normal levels. plus, when you go in there to check, you are raising the levels just being in there breathing.
I would start by calibrating your reader

plants use CO2 and put out oxygen. i have read that they photosynthesize all day, using CO2 and water to produce sugars which the plant then uses at night to grow. i also read that 1500 ~ 2000 ppm is ideal for cannabis.

Thanks Chuck -- but all that diagram did was prove my question was valid. Plants give off co2 at night -- my question is, in a room with around 10 plants sleeping, is that going to substantially raise the ppm in the room.

A) The accuracy of the meter is somewhat irrelevant -- even if the calibration is off, the relative change is still the same -- the room is going up by 400-1000ppm above normal levels when nothing would otherwise be in it.
B) I know me being in the room raises it - these are fresh checks as I'm walking into the room before the meter has adjusted to my presence.
C) I'll have to check the brand, but it's a meter that's only a couple of months old and came factory calibrated and not a cheap meter (includes a hygrometer) -- so far it has matched when my controller turns the co2 on (co2 tank has been off for over a week and is empty), so pretty sure the calibration is pretty on. Either way the ppms go up in the room even if the calibration is not on 100%. There was actually a reading of almost 2k ppm at one point when I came in the room yesterday.

I don't really need a bunch of comments that are not to the point of the question. Yes or no -- is it possible that a bunch of plants in dark phase can raise the ppms that much in a room. If the answer is no possible way, it must be something else and I'm fine with that. It just seems very coincidental as this was not going on in the room before I divided it into two chambers and I actually had to run supplemental co2 at that point to get it to these levels.

i have nothing to add and im not subscribing so ill never hear your reply, I just hate it when people try to limit the posts in "their" thread so I thought I would post something. muahahahaha

Too bad this site doesn't have a Dislike button... is it too really too much to ask a question and expect a response to that actual question instead of a bunch of side issues you weren't asking about? I actually thought I was in the advanced cultivation thread and might get a more advanced than usual response

Plants do leach carbon dioxide during dark periods when they are not actively photosynthesising, but it will always be a net-negative amount. So the answer to your question is no. I also have to agree with Chuck, something seems way off with your readings.

ReefBongwell said:

Too bad this site doesn't have a Dislike button... is it too really too much to ask a question and expect a response to that actual question instead of a bunch of side issues you weren't asking about? I actually thought I was in the advanced cultivation thread and might get a more advanced than usual response

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Ya, it is too bad.

akula said:

Plants do leach carbon dioxide during dark periods when they are not actively photosynthesising, but it will always be a net-negative amount. So the answer to your question is no. I also have to agree with Chuck, something seems way off with your readings.

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Thanks I'm not sure that I buy the meter being off still, but appreciate the stateforward answer that it should be a net negative.

Plants only need co2 when the lights are on...

I'll say what others did (not that you are really listening). Your meter seems kinda phucked. 800!! Ummm no.

I have 14 monsters in a sealed room. The ppm of co2 goes up about 50 ppm during lights out. You must live next to a major freeway or something to have ambient readings above 400

I have ~1000 ambient in my grow room from my gas furnace and water heater.
down to about 800 now with temps rising and the heat running less.

do you have gas or electric?

ReefBongwell said:

Thanks Chuck -- but all that diagram did was prove my question was valid. Plants give off co2 at night -- my question is, in a room with around 10 plants sleeping, is that going to substantially raise the ppm in the room.

I don't really need a bunch of comments that are not to the point of the question. Yes or no -- is it possible that a bunch of plants in dark phase can raise the ppms that much in a room. If the answer is no possible way, it must be something else and I'm fine with that. It just seems very coincidental as this was not going on in the room before I divided it into two chambers and I actually had to run supplemental co2 at that point to get it to these levels.

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The simple answer to your question is YES the plants can produce a significant amount of CO2, especially if they are in a fast growth stage. All those extra sugars produced when the lights are on are being burned, That also means they are consuming an equivalent amount of O2. Its a good idea to have some fresh air intake and circulation in a crowded grow room during the dark period.

It was the meter Although the ppm in that room with the plants is higher than a normal room.

Yeah I actually put a fan on in there in the dark tonight it's getting pretty humid in there and i'm catching an ammonia smell... not sure if that's from the plants or it's humid and my cat pissed in there at some point in the past... he has been locked in that room 2 or 3 times this week (fucker is always sneaking in and then i leave and shut him in without knowing). He probably pissed in there. Fucker.

Circulation, definitely. Fresh air, not necessary. There is PLENTY of o2 in the air to enable respiration.

And not to get too far off topic but more of an FYI: cannabis is a C3 plant which means that it can use (through respiration) sugars throughout the day and night. C3 plants don't magically switch from fixing sugar to breaking it them apart and using them once the lights go out. Which is why you can grow under 24 hr lights on with no detrimental affects. The literature I have read stres that respiration is slightly higher during lights off, but it is pretty insignificant increase.

Soooo. Plants are absorbing AND expelling co2 and o2 all the time. The reason growers add co2 is that c3 plants can take advantage of greater than average percentages of co2 and therefore, fix sugars at a higher rate. From my understanding, the required o2 levels for respiration to occur are soo low that if it ever got to that level you would basically suffocate when you entered your room.

The down side of this...for you desert growers, is that with high heat AND low humidity, your plant will be respiring faster than it can uptake water. It will close its stomata to reduce water loss..and bam. No more co2 is absorbed for production. What the plant then does is a very wasteful process of using rubisco to creat sugars by combining o2 with Rubp instead of co2. This is half as effecting and also creates a toxic C molecule that has to be broken down. I can't remember the specifics but it makes some sort of glypholate? Acid that then has to be evbtually broken down into glycine I think it is?

At any rate, don't let your room get hot and dry! 80-85 and around 20% humidity would start creating problems.

ReefBongwell said:

It was the meter Although the ppm in that room with the plants is higher than a normal room.

Yeah I actually put a fan on in there in the dark tonight it's getting pretty humid in there and i'm catching an ammonia smell... not sure if that's from the plants or it's humid and my cat pissed in there at some point in the past... he has been locked in that room 2 or 3 times this week (fucker is always sneaking in and then i leave and shut him in without knowing). He probably pissed in there. Fucker.

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My fucking cat does the same thing! Crazy.

ReefBongwell said:

i'm catching an ammonia smell... not sure if that's from the plants

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I thought that once too with blueberry, it was the plants lol

i run my co2 all the time in my sealed room... sometimes in the nigh the leaves will be downward alittle like normally would without 1500ppm an normal air.

but i can tell when co2 is makinf a difference. i have a couple hundred tops in one big ass scrog and every single leaf is up and spread out an just look awesome... night and day they will be like this as long as co2 burner is on an ppms at 1400-1500. so they must like the extra co2 at night also.

Huel Perkins said:

Plants only need co2 when the lights are on...

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yeah i'm pretty sure the whole point of co2 supplementation is to speed up your plant's photosynthesis process which allows them to uptake more water, nutrients, light etc. so why would you be worried about the ppm levels at night?