CO2 Made Simple

By Glen Babcock
Published: November 1, 2014 | Last updated: April 21, 2021 07:17:58
Key Takeaways

Carbon dioxide may be invisible and odorless, but to a plant it’s the best thing ever. To make the most of it in your growroom, just follow these simple guidelines.

Source: Sofiaworld/

Carbon dioxide is one of the driving forces behind photosynthesis. When it is combined with water and light, plants are able to create the energy they need to grow and stay healthy. One of the by-products of photosynthesis is chlorophyll, which is what gives plants their green color. Another by-product is the oxygen humans breathe in. Without plants, living on planet Earth would be a mighty tough challenge.


The importance of providing indoor gardens with supplemental CO2 has been known for a long time now, but the process was often thought to be cost-prohibitive. Fortunately, there are a number of affordable methods of supplementing CO2 now available. No longer can a grower say boosting CO2 levels indoors is too expensive—the benefits growers see in their yields and plant quality far exceeds the costs associated with adding CO2 to their garden. Let’s take a closer look at CO2CO2, starting with some tips on how to use it efficiently, no matter your growroom configuration.

In a sealed growing environment, it is best to think from the top down. Carbon dioxide is made up of one carbon molecule and two oxygen molecules. This configuration of molecules makes the gas heavier than oxygen, which causes it to drop to the bottom of the grow area. When plants are present, this falling CO2 is trapped by the stomata on their leaves, where it is converted to oxygen, chlorophyll and energy. Simply put, whatever your preferred dispersal method of supplemental CO2, it is best to place it above the plant canopy if your growroom is sealed.


Some growers need to ventilate their grow space, most often because of heat and or humidity issues. The most common way of doing so is to bring fresh air into the growing space down low and force the exhausted air out higher up in the space. In this situation, having your CO2 source up high is of little benefit to your garden. Most of the gas is exhausted before the plants can even use it. It is a much better idea in this scenario to place the CO2 source down low, close to the fresh air intake. From this location, CO2 is pulled up through the canopy by the force of the air being drawn in. The CO2 rises and the stomata are able to make use of it.

Also keep in mind that air temperatures affect plant growth, and the effects of extremely warm temperatures, which stresses plants out, can often be alleviated with adequate CO2 levels. With enough added carbon dioxide, plants are better able to tolerate extreme temperatures. In growrooms without supplemental carbon dioxide, plants just simply can’t tolerate the heat. They begin to wilt and will subsequently die.

Next, it’s time to think about the various plant stages of growth and how CO2 helps during these different phases of life. Clones or cuttings will root much quicker when in the presence of low-to-medium levels of CO2, typically around 800-1,000 ppm. Not only do they root faster, but they will grow up to become overall healthier plants than clones or cuttings grown without CO2.


During the vegetative stage, CO2 makes for much more vigorous growth, which leads to more flowering or budding sites, and ultimately increases yields. CO2 levels of 1,200-1,500 ppm are ideal during the vegetative stage. Finally, during the flowering stage, CO2 acts as a flowering booster. It will increase flower size and also makes for a much better finished product. As with the veg stage, CO2 levels of 1,200-1,500 ppm are perfect for growing great flowers.

In a nutshell, CO2 is extremely important to plants. Without it, your plants cannot reach their maximum potential. With the many affordable options available, growers should consider providing extra CO2 for their gardens. The healthier plants and increased yields that come as a result make this move a no-brainer.


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Written by Glen Babcock

Profile Picture of Glen Babcock
Glen Babcock is the owner of Garden City Fungi and the founder of ExHale Homegrown CO2. Glen has been involved in Agriculture his entire life. Glen graduated from the University of Montana with a degree in Forestry and has been a mycologist for over 23 years. His research has been published in scientific journals worldwide.

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