Air exchange, co2 and monitors

I'm experimenting with minimal air exchange to keep humidity and temperature up in the winter. No one seems to know how much air exchange is needed, the answers are all over the place and there are always variables. I know from experience that I can use much less ventilation than many/most people say, but I'd like to know what my co2 levels are. I'm thinking about an Autopilot APCEM2, APCEMDL, or possibly the new InkBird ICC-500T.

Does anyone now if cheap monitors like these are any good?

Depends on biomass. More plant = faster CO2 consumption. If you have things dialed and the plants are growing fast your CO2 levels will drop according to the biomass, so in the beginning it may take 3 hours to drop 100 PPM and during peak mid flower it may only take 10 minutes. So the more biomass there is within the fixed volume of grow space the faster the CO2 levels will drop.

I have several of the Autopilot Desktop loggers and I love them.

You could step it up a notch if you wanted to control your fan with a CO2 PPM controller then you can have it kick on when the CO2 levels drop. Just have to make sure the controller will support the lower PPM setting and small dead band. Using a timer to maintain CO2 is going to require adjustment as the biomass increases.

Renfro said:

Depends on biomass. More plant = faster CO2 consumption. If you have things dialed and the plants are growing fast your CO2 levels will drop according to the biomass, so in the beginning it may take 3 hours to drop 100 PPM and during peak mid flower it may only take 10 minutes. So the more biomass there is within the fixed volume of grow space the faster the CO2 levels will drop.

I have several of the Autopilot Desktop loggers and I love them.

You could step it up a notch if you wanted to control your fan with a CO2 PPM controller then you can have it kick on when the CO2 levels drop. Just have to make sure the controller will support the lower PPM setting and small dead band. Using a timer to maintain CO2 is going to require adjustment as the biomass increases.

Click to expand...

I like toys and hadn't bought myself a Christmas present yet so I ordered the Autopilot APCEMDL for it's logging capability. (I'm more of an experimenter than grower.) I hope to collect some good data to share on the air exchange needed for sufficient CO2. Who knows, maybe I'll even get an airflow meter, but I think whatever fan(s) I use should give a good idea of the situation.

I already have a 2 week old started in my high tech sealed and insulated grow cabinet....... a 36 quart cooler stood on end.
An Inkbird controller maintains 82F air temp and another monitors humidity. Light is 4k COB for now. It's doing fine with no real ventilation, but it gets some air when the door's opened. That, and I cheat! I blow in through a hose and raise the humidity to 70% after the doors been opened and closed. We'll see what that does to CO2 levels.

I'll go as far as I can in the cooler and the data should help guide me to the next setup. It could be the tent, my original cardboard cabinet or my new insulated grow chamber design.... with a couple secret innovations.

Renfro said:

Depends on biomass. More plant = faster CO2 consumption. If you have things dialed and the plants are growing fast your CO2 levels will drop according to the biomass, so in the beginning it may take 3 hours to drop 100 PPM and during peak mid flower it may only take 10 minutes. So the more biomass there is within the fixed volume of grow space the faster the CO2 levels will drop.

I have several of the Autopilot Desktop loggers and I love them.

You could step it up a notch if you wanted to control your fan with a CO2 PPM controller then you can have it kick on when the CO2 levels drop. Just have to make sure the controller will support the lower PPM setting and small dead band. Using a timer to maintain CO2 is going to require adjustment as the biomass increases.

Click to expand...

Of course Renfro has the info! Can you please tell us for non CO2 supplemental growers how often we should exchange air in full flower assuming we have filled up the room reasonably as far as volume. When does the CO2 level begin to drop if we dont move air faster?

ComfortCreator said:

When does the CO2 level begin to drop if we dont move air faster?

Click to expand...

Thats such a big variable, it doesn't take a ton of air exchange to keep ambient CO2 levels but how much exactly will change as the plants grow. Biomass is a huge factor and if things are dialed and the stomata are open then plants can really use CO2. So when you start small plants in a big room the biomass is almost not a factor but when the plants have filled the space and are in mid flower peak growth they can really consume some CO2. The only way to really know whats going on in your environment is to grab a CO2 meter like the Autopilot Desktop CO2 monitor. This will let you log the data and see exactly what is going on in your room as the plants grow.

Thx there are 500 choices for CO2 monitors. I will get the Autopilot for next run and start a thread.

ComfortCreator said:

Thx there are 500 choices for CO2 monitors. I will get the Autopilot for next run and start a thread.

Click to expand...

If all you intend to do is monitor CO2 levels then that model works great. They make a model that will accept a memory card so you can put the data in your PC, it's like $20 more. I have three of the ones that don't take a memory card. I like being able to hang one anywhere and get numbers. Makes it easier to detect a micro climate, at least before I got the IR camera, that really makes it easy to look at a room and see areas where the temperature varies, areas that may lack circulation.

A quick update....

Good news, been using the Autopilot C02 logger and haven't seen any significant C02 depletion from minimal ventilation.
An Inkbird IHC-200 humidity controller runs a small exhaust fan to maintain 68% RH.

An Inkbird ITC-308 temp controller powers a heat mat or USB humidifier (in the tent) to hold a steady 28C/82F during lights on. The young plant doesn't transpire much and the little USB humidifier works like a charm, no more running the big one to humidity the whole room.