That's good at 85*F. Probably don't want to see any hotter than that as they'll herm easier.

I have run Co2 for 11 years and 85 is the sweet spot. The room I run it in is 12x14x8 so I run at 1900ppm which gives me my 1500ppm all around the room. Here is a short read on it.



First a little Plant Science 101 - For a successful, productive garden, hydroponic, indoor and greenhouse growers must control six "essential elements" - air, light, nutrients, water, humidity and temperature. Remove or alter the ratio of only one of these elements, growth will slow, and plants could eventually die. In this article, we will review the air element, specifically carbon dioxide (CO2), it's role in the most vital plant process - photosynthesis - and how to effectively implement CO2 systems.

Photosynthesis begins when stomata, pore-like openings on the undersides of leaves, are activated by light and begin breathing in carbon dioxide (CO2) from the air. This CO2 is broken down into carbon (C) and oxygen (O). Some of the O is used for other plants processes, but most is expelled back into the air. The C is combined with water to form sugar molecules, which are then converted into carbohydrates. These carbohydrates (starches) combine with nutrients, such as nitrogen, to produce new plant tissues. CO2 is vital to plant growth and development, and yet is often the most overlooked element in indoor gardening.

Successful indoor growers implement methods to increase CO2 concentrations in their enclosure. The typical outdoor air we breathe contains 0.03 - 0.045% (300 - 450 ppm) CO2. Research demonstrates that optimum growth and production for most plants occur between 1200 - 1500 ppm CO2. These optimum CO2 levels can boost plant metabolism, growth and yield by 25 - 60%.

Plants under effective CO2 enrichment and management display thicker, lush green leaves, an abundance of fragrant fruit and flowers, and stronger, more vigorous roots. CO2 enriched plants grow rapidly and must also be supplied with the other five "essential elements" to ensure proper development and a plentiful harvest.

Commercially available CO2 generators offer the most economical, practical and consistent method of enriching indoor gardens. Using atmospheric control systems in conjunction with CO2 generators, ensure the most effective production and use of CO2.

Atmospheric control systems with automatic override or defeat, and CO2 monitoring logic, enrich and maintain optimum levels in the environment during the photo (light) periods, when most plants can absorb CO2; and they defeat CO2 production during dark periods. Automating your CO2 enrichment system pays for itself quickly with shorter crop cycles, improved quality and higher yields.

When enriching an indoor garden with CO2, proper light is essential for effective assimilation. For plants to use CO2 efficiently, light spectrum and intensity should be appropriate for the plant species in your garden. Remember - CO2 enriched plants under intensified lighting demand higher levels of nutrients, water, space and room temperatures of 80-85 F. (27 - 29 C.).

As CO2 is a critical component of growth, plants in environments with inadequate CO2 levels - below 200 ppm - will cease to grow or produce. And, growers should be cautious when experimenting with CO2 levels above 2000 ppm. CO2 is heavier than oxygen and will displace the O2 required by both plants and human to function and live. (FYI: OSHA max allowable for human exposure is 5000 PPM). So, air circulation and ventilation is critical to profitable CO2 enrichment.

Plants use all of the CO2 around their leaves within a few minutes leaving the air around them CO2 deficient. Without air circulation and ventilation, the plants' stomata are stifled and plant growth is stunted.

Proper air circulation with oscillating fans and in-line blowers, will eliminate potential stagnation problems and ensure efficient CO2 enrichment.

If you have never enriched your garden with CO2, start with 700 - 900 ppm (double the normal atmospheric levels). If yields improve, increase CO2 enrichment to 1200 - 1500 ppm. If there is no response to the CO2 enrichment, double-check your other five "essential elements" to ensure they are not limiting factors.

Stomata and how they work

Here are some images of how it all works, :party0044::party0044::party0044:

Excellent info. woodsman.

Do you reduce temp by 10F at night as well?

My room settles at 74 for the night so I just leave it there, mid 70's is good, +- a couple degrees won't make that much diff.

Smokey W

Woods is kickin good knowledge here. Thems the charts I was mentioning on ur thread Woods.

if you are new to co2 you may keep ur day temps a little cooler and co2 a little lower to start til you get a good feel for your plants. If you are having any heat stress or def issues it can progress quickly when at full speed in the sweet spot... just a thought.

Will do!

woodsmaneh said:

My room settles at 74 for the night so I just leave it there, mid 70's is good, +- a couple degrees won't make that much diff.

Click to expand...

Hey woodsman, do you raise your night temps in the first few weeks of flower to reduce stretching at all??

Cheers dude

One more chart for the newbies; vpd, out WHERE to keep your rh once you've set your temps;

how exactly do you interpret the numbers in the boxes for the VPD please dude??

bobby34 said:

how exactly do you interpret the numbers in the boxes for the VPD please dude??

Click to expand...

First, find the temperature of interest on the left side of the chart. Then, read across to the green box. At the top of that column will be the RH% that's appropriate for that temperature.

For example, 75% RH @80 F sounds insane, right? Check the chart; it actually says that's on the money, and if you get any warmer at all, 80% is even better!

GOOD LORD, WHY?! Aren't all my buds gonna rot and fall off?! NO. As it turns out, this is the climate most pot grows in naturally. Not only is this the lowest stress condition for RH relative to temperature, it also maximizes plant growth due to minimizing the energy that has to be diverted from growing towards transpiring more water to avoid wilting in a drier environment.

Moreover, at this level of humidity the plant's ability to take up atmospheric CO² is also maximized, which if it's supplemented can now finally live up to the promise of helping your plants grow bigger and faster. If your environment is too dry, CO² augmentation is useless as the plants can't take it up.

Superb,, thank you very much!!.

bobby34 said:

Superb,, thank you very much!!.

Click to expand...

This tip is really worth the 30% that everyone throws around about CO². My bill is in the mail...

HA HA roger that!. Cheers again dude

How far into flower are you running the high RH?

high temps are the only way to rock sealed rooms..

co2 as its own variable actually causes plants to close their stomata a bit so running higher heat opens them back up. I had big issues running sealed rooms at ~74-76f with low rh (because of mini-split) in veg. Turn down a/c maybe turn on a humidifier and crank temps ~10 degrees and plants go crazy.

veg-85f 60%rh
early flower through stretch-85f tapering down to 81/82 rh 50-60%
after stretch through finish-78-80f rh 40-50% ; colder night temps

CaliShark said:

How far into flower are you running the high RH?

Click to expand...

I'm only trying to bring RH down during flush- which for me only lasts 4 days or so. My idea of 'down' is 60s, though.

why risk having such high rh through flower?

You could lower feed strength or have less fan wind on plants and maintain a lower rh with the same results as high, but not as much mold risk..

pussOGbrah said:

high temps are the only way to rock sealed rooms..

co2 as its own variable actually causes plants to close their stomata a bit so running higher heat opens them back up. I had big issues running sealed rooms at ~74-76f with low rh (because of mini-split) in veg. Turn down a/c maybe turn on a humidifier and crank temps ~10 degrees and plants go crazy.

Stomata open and close depending on RH and heat, with low RH they are not running at optimum, so High RH and the right temp allows the stomata to open fully and eat all that Co2. As a rule I let RH float for the last 10 days and it goes from 60% down to 35% with lights on, does it simulate fall? Don't know but I stop Co2 for the last 14 days also.






veg-85f 60%rh
early flower through stretch-85f tapering down to 81/82 rh 50-60%
after stretch through finish-78-80f rh 40-50% ; colder night temps

Click to expand...

pussOGbrah said:

why risk having such high rh through flower?

You could lower feed strength or have less fan wind on plants and maintain a lower rh with the same results as high, but not as much mold risk..

Click to expand...

Sorry this is not correct. Low RH limits the opening on the Stomata (slows growth) as they regulate moisture loss, one reason leaves cur-up to preserve moisture. High RH allows them to open right up and go to town on all that extra Co2. Running low RH is counter productive, lots of guys skipped that Botany class in high school.

Peace