CO2 dark period toxic?

Hey everyone.

I have seen this topic discussed some on this forum and I was reading Spurr's post about CO2 and really couldn't come to a definite conclusion so I thought I would start a small discussion about it.

Here is my issue:

Vegged for 3-4 weeks in my sealed room at 74 degrees, 50% RH, 12 K metal halide adjusta-wings. 3 gallon pots, all plants perfect, not one deficiency, stress sign or unhappy girl in the bunch of 90. CO2 was not supplemented in veg, so ambient was 400-500 constant with the monitor.

This past week we transplanted into 10 gallon containers. About a pallet of fresh soil was put in the room. Inoculated with a strong tea and off to the races! I started supplementing with CO2 to about 900 ppms. They seemed to take the transplant pretty well. Today, about a week later, I notice some heavy drooping in about 10-15 of the plants. Check for watering, not dry at all. Seem to not have eaten since the last watering. Check my nighttime CO2, keep in mind I only supplement to 900, and ppms are 1300-1400...

I shut off the CO2 today. They are lights on back down to their 400 range. I hope this corrects the problem, or what I think the problem is.

CO2 toxicity, basically drowning the plants roots at night time. I have read up on soil respiration and plant gas exchange. Plants give off CO2 at night, and soil constantly gives off CO2, especially soil dominated by healthy bacteria. Bacteria produce CO2 as a by product.

So I ask, are CO2 levels above 500ppm, hindering my plants from thriving and ultimately dying? Should I dump the room when lights go off? 1 time? full time? Any input is appreciated.

PS: The room down the hall has a huge undercurrent system in it. Same type of issue with high CO2 at dark time but the plants are fine. Only reason I can think of is because they have a air stone supplementing air to the roots 24/7...

Update.

Installed a filter/fan combo, 8inch with can 100.

Put the fan on during dark periods, emptied the room down to 490 ppm co2. Plants turned up, praying, less than 6 hours.

It was def. either a issue of too much co2, or just not enough fresh air at all for the root zone. Everything is feeding heavy again and luckily didn't have an effect except a couple plants with some mag issues. Foliar feed and back to watering.

So in a totally sealed room I have to dump air during lights off. This was done by cracking the AC just enough to create some negative pressure. Boom co2 ppm dove down, and plants loved it.

T

dont you have a CO2 monitor?

there's no need to supplement at night, though 1200 ppm isn't going to do anything bad. CO2 will hurt you before it hurts plants, I'd imagine. Get a CO2 monitor to switch your tank or gen. on, make sure it has a photosensor to you can select the option to have it auto shutoff at night.

i have often said that the air pump to the rez should be keep out side the room when running a sealed room and hydro ,this helps me belive i am right ,thanks for posting this up very helpful

co2 at nite?never,
lites "ON " only

all kind of air movement at nite but no co2

wantaknow said:

i have often said that the air pump to the rez should be keep out side the room when running a sealed room and hydro ,this helps me belive i am right ,thanks for posting this up very helpful

Click to expand...

dont think so

multilpe air pumps 10 or so with a 20 lb tank ,tank last 10-14 daze,for 22 bucksrunnin at 1100ppm


so without any facts I call bs

air pumps will cause co2 problems? heres a couple more for shits and giggles

gram a watt on that one

should we keep going
1 + grams a watt and every pump was in a sealed room your talking a bunch of bull

myth busted

sorry jm ,my room only 5x 9 x7 tall ,not a wherehouse like yours .lol,no controles just a timer ,and like i say to the others like you ,better safe than sorry ,what harm could possable be done by putting the pump outside the room ?but i see your point with a large set up like you have

I don't think anyone is supplementing co2 at night.

The plants naturally expel the co2 that they took in during the day. As soon as the lights come on they suck it all back up.

My co2 climbs from the minute the lights turn off until the lights come back on.

Did you use a burner or bottled co2 to increase ppm value?

In the first case, to produce co2 you're lowering O2 level as the oxygen is used to form O2 (from air) + C (from gas) = CO2.

Said this if you have a sealed room, at the end of the plants day the O2 level in the room will be probably low.

And take in consideration that oxygen is needed 24/7 but the most important time it should never miss is in the night, when photosynthesis stops and cellular respiration rate increase to produce chemical energy to spend the day after.

So if you're using a generator I think this could be the issue. If you're using bottled co2 this lowering in O2 is not noticeable as you're not going to use it to produce co2 and the issue is something else.
I said this because I used co2 in the past, and even with high value at night I din't see any trouble, and I used bottled co2.

However, I suggest you to do a couple or even three complete air-changes during the night. It will help to keep O2 at high level and if you're using an hydro setup...some H2O2 could be a good supplement during the night.

Hope it helps

Hey there,

I am using bottled CO2. Sorry it was confusing in that post, I don't supplement at night, but the room was trapped so it just climbed to 1300-1500.

After installing the fan combo and dumping the room at night, girls immediately stood back up. crazy...

There was no O2 at all left for them to breathe in the room after it being sealed for days with just CO2 supplementation.

On another note, I have also not seen any problems with running air pumps in a sealed room with 1000ppms of CO2. We have about 96 trees in a sealed room with 1 air stone in each pot, runs fine

The conclusion is:
Don't trap air in rooms at night, you must dump the air. I dump all night, seems to lower humidity and clears the room.

T

anferneybra said:

After installing the fan combo and dumping the room at night, girls immediately stood back up. crazy...

There was no O2 at all left for them to breathe in the room after it being sealed for days with just CO2 supplementation.

Click to expand...

If you're supplementing bottled co2 it's pretty impossible there was no oxygen in the room. Bottles contains CO2 wich is C (used by plants) and O2 depleted by leaves and then used by roots. However the quantity of O2 obtained from the CO2 is not enough for the crop, especially during long periods.

On another note, I have also not seen any problems with running air pumps in a sealed room with 1000ppms of CO2. We have about 96 trees in a sealed room with 1 air stone in each pot, runs fine

Click to expand...

Because it's not a CO2 issue. It's a lack of oxygen. They are different things.

The conclusion is:
Don't trap air in rooms at night, you must dump the air. I dump all night, seems to lower humidity and clears the room.

Click to expand...

Easy and effective

One major advantage to running a sealed room is the you bring in no outside air, thus no mold spores, mildew, fungus ect.

Running an exhaust fan would completely remove that advantage.

My sealed room seems to run just fine for what's it's worth.

I think when people think of a sealed room they think its sealed so they don't lose CO2.

At least that is what I think, and that's what I am going for. There was obviously a problem that I quickly diagnosed, and corrected, and the plants showed it. Drooping hard, not eating, start of chlorosis. All signs of over watering precipitated by a lack of O2 in the root zone. The sheer fact my meter read 1300-1500 ppms of CO2 just gave me a early warning that there was a problem at night.

I dumped the room, and one night later they are standing tall. Now I have been dumping the room every night, eating is where it should be and the girls are stretching hard in their first week of flower.

As far as night time goes, I could care less if the room is sealed since I am exchanging air. I am not talking about some small room, I am talking 90, 5 foot trees in 10 gallon pots, upped to 20k watts in flower from 12k in veg. This is a 22x22 room with 11 foot ceilings. I have a carbon filter on the intake and a carbon on the out, nothing in or out with air exchange

Not saying sealed doesn't work, but for organic soil, root zone health is paramount. The two 20k hydro rooms have no problems with no air exchange because they supplement O2 to the root zone via stones in each bucket. Soil relies on the air around which needs to be O2 rich just as much as CO2.

Just my learning process, and something not a lot of people have run into from what I take. Talked to 3 or 4 growers with more commercial runs than I, and they thought I was on the right track but had never run so much in such a sealed room. They had always exchanged air, and now we know

T

You can do both--sealed room (little to zero air escaping) and bring in fresh air from outside (which includes naturally produced CO2 and oxygen).

BTW...in nature, is there a "CO2 God" that turns off the valve at night--and then during daytime, the CO2 valve is turned on? LOL...but during daytime plants will exchange greater quantities of CO2...than they do at night.

I have electric dampeners that open and close at the appropriate times to exhaust the stale air from my "closed environment" and replace it with fresh air several times during "nighttime"...and the dampeners remain closed during the "daytime" to provide me with a "closed environment".

Also...supplementing outside air into the closed environment 24/7 will cause a slight positive air pressure (harder to close the door), but you gain bonus points since the air is cooler--provided you run flower "daytime" during the real world nighttime. I flower 9PM to 9AM, and bring in the cooler night/early morning air. Although the outside air does have fair levels of CO2...it is not enuf for me. So when lights are on, I supplement the CO2 with bottled gas...which allows me to combine "free CO2" (outside air) with "purcha$ed CO2"...and I pocket the $aving$ (since use less bottled gas to achieve the desire levels of CO2 ppms).

Cheers!