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How to Implement CO2 to your Grow

Carbon Dioxide Supplementation in Cultivation Facilities

Every cannabis grower's dream is to harvest big, sticky buds. To increase plant yield, indoor growers pay attention to the big 3: water, nutrients and light.

However, modern growers know adding carbon dioxide to the grow space can also benefit them by increasing their crop.

Why do cannabis plants need CO2?

Like all other green plants, cannabis transforms light energy into chemical energy through a process called photosynthesis. Chlorophyll-containing organelles known as chloroplasts use sunlight to convert CO2 and H2O (water) into carbohydrates (sugars) plants use to grow.

Fortunately for us, oxygen is a by-product of the process. It is released by the plants during the day as they absorb CO2. Both gases are released and absorbed via the plants’ stomata, small openings surrounded by guard cells on the undersides of their leaves.

If a cannabis plant does not get enough CO2 they will continue to grow until their stored sugars are depleted. Once that happens, their metabolism decreases, and they will stop growing.

On the other hand, if a plant gets too much CO2 it will slow down or even stop photosynthesis. The trick is finding the right CO2 level for a grow space to maximize photosynthesis and yield.

What does adding CO2 do to cannabis?

Increasing the amount of CO2 in the air for your grow space, can help cannabis plants and promote faster growth and productivity. This is in part due to photosynthesis being directly linked to the amount of CO2 available to the plant.

If you are looking to accelerate the growth cycle of your crops its important to consider adding additional carbon dioxide to your space. Studies have shown that adding CO2 can accelerate and increase CO2 levels to around 1,500ppm. 

When to use CO2 in your grow room

When is the right time to introduce carbon dioxide in an indoor grow environment?

For those that are looking to add carbon dioxide to their grow room, the flowering stage is the most important. It is critical that when you supplement CO2 to your crops you do so within the first 2-5 weeks of flowering. Assuming your light, heat, water and nutrients are fine-tuned, his can boost overall crop size by 20-25%.

Best way of adding CO2 to grow tent

CO2 makes up about 0.04% or 400 ppm of fresh air. Double or triple that in an enclosed greenhouse and you may get sleepy sitting inside it, but your plants will thrive.

The easy way many small growers add CO2 to their grow room is by hanging slow-release CO2 bags or bottles. They constantly produce CO2 over several days. A rule of thumb for an enclosed space is one co2 bag per 4x4 area or per 4x4 grow tent.

For large-scale operations, growers use tanks of compressed CO2 or CO2 generators in order to automate delivery and send the CO2 gas down through pipes for an uninterrupted supply to your crops.

In addition to CO2 supplementation, you should use a CO2 monitor to test the  CO2 levels over time. This will let you know when you need to replace your CO2 bags and if your plants are getting the right amount of CO2.

How much CO2 Is enough?

The optimal amount of CO2 required to boost the yield of cannabis plants depends on several factors including the intensity of the light and the size of the grow space. In an indoor space with normal fresh air ventilation, the  CO2 concentration should be around 400 ppm. This leads to growth rates like what you would expect if you were growing your plants outdoors.

Growers have achieved the best success with CO2 levels between 1,200ppm and 1,500ppm. However, you cannot simply increase the CO2 level unless your plants can use it.

CO2 and Light

If you are growing your cannabis plants under low light (around 12,330 lux/1150 fc), you can increase their photosynthesis by maintaining CO2 levels at 400ppm. For additional growth you will need to increase the intensity of your grow lights.

Increasing the light intensity to somewhere around 49,310 lux/4600 fc allows you to increase the CO2 level and therefore, plant growth. The rate of photosynthesis will speed up as you raise the CO2 level to 600 ppm. Beyond that, the rate will increase more slowly. You can increase the level to as much as 1200 ppm under that lighting, although photosynthesis will be even slower.

If you can increase the light intensity to 59,201 lux/5500 fc, your cannabis plants can use increased CO2 levels of 1200-1300 ppm. You could increase the level to 1500 ppm if your light intensity increases to 80,400 lux/7500 fc. Growers who have taken it to that level recorded a 100% increase in their plants’ growth rate.

Calculating the amount of CO2 required

Before starting your grow, take the time to work out how much CO2 your space needs.

For example, to raise the CO2 level to 1,000 ppm in a room that is 4m long, 4m wide, and 3m high (4x4x3 = 48) you'll need 0.048 (48x0.001=0.048) cubic meters of CO2 gas. 

For further resources, check out our CO2 Calculator for Grow Room or Indoor Greenhouses.

Where should CO2 monitors be placed?

When using a CO2 monitor or controller, it should be placed at canopy level and moved higher as the plants grow.

When installing a CO2 safety device you should place it 12 inches (30cm) from the floor.

Best CO2 system for your grow room

The "best" system depends on your budget and requirements.

  • CO2 grow bags and a CO2 monitor are an inexpensive way to get started and can improve yield in a small grow tent. The CO2 monitor will tell you when to replace the bags.
  • CO2 generators use gas, flame and produce a lot of heat. Therefore, they really only make sense in large commercial greenhouses.
  • CO2 tanks and controllers are by far the most common used today.  While they have a high up-front cost, they not only provide precise CO2 control to maximize yields, but because they can be used in a sealed room they enable greater security for the grow space.

As a reminder, it is important to note that when using CO2 tanks and controllers, CO2 leaks can be dangerous. Although CO2 is beneficial for plants - it is hazardous for humans. You should always ensure proper CO2 safety detection for indoor grow spaces.

CO2 Safety Monitors and Controllers for Growers

Best CO2 monitor for your grow room

Indoor CO2 Controller and Sensors

When it comes to best CO2 monitoring devices for your grow room, CO2Meter specializes in carbon dioxide solutions for any indoor grow space, requirements, and production set-up.

Below are just a few of our CO2 monitors, controllers, and sensors for indoor agriculture, greenhouses, grow rooms, or hydroponic shops


Using CO2 safely and correctly in your grow space may be the final step you need to take for a healthy crop. If you are not achieving the right levels of CO2, you may well be missing out on the best possible yield.

See the below for more tips, guides, and resources for your grow space:

For more information on CO2Meter.com sensing technologies or indoor air quality devices contact us today.

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