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Proper CO2 Handling For Indoor Cultivation

June 25, 2019

  • Using Carbon Dioxide for Cultivation
  • Compressed Gas Cylinders
  • Residential Cultivation Using CO2
  • Commercial Cultivation with Green CO2

Using Carbon Dioxide for Cultivation

Carbon dioxide (CO2) is a colorless, odorless, non-flammable gas that is required by plants in order to grow. When CO2 levels dip below a certain amount in the environment, growth begins to slow down. By adding supplemental CO2 to your grow rooms, you can stimulate optimal rates of growth. Plants will be able to grow faster by being able to uptake more light, water, and nutrients. Cannabis plants will produce more foliage in less time, but not necessarily aiding in producing more potent cannabis buds. However, many individuals have observed that the cannabis nodes in flower become more densely packed and that the first set of flowers are more likely to set early if supplemental CO2 is applied. This is why it is important to apply additional CO2 during the vegetative and early flower growth stage. Cannabis plants thrive on about 1200-1500ppm of CO2, but it can be toxic to humans at 5000ppm or more which is why it is important to use a sensor (Virtra, 2014). Carbon dioxide enrichment is widely used in commercial cannabis indoor facilities today and have been in use in commercial greenhouses for decades although it is important to note that plants need other critical elements for life in order to benefit from supplemental CO2 otherwise it may be wasted.

Indoor CO2 storage

Image of CO2 cylinders located inside a cultivation facility.

Compressed Gas Cylinder

There are many ways to raise the CO2 levels in an indoor grow room. The most popular method is to disperse CO2 from a cylinder or tank. Compressed CO2 systems are almost risk-free because they do not produce any toxic byproducts, heat, or water. The CO2 is measured out of a cylinder using a system comprised of: a regulator, flow meter, solenoid valve, and short-range timer in residential and commercial settings. Metal carbon dioxide cylinders can be purchased from a welding, hydroponic store or beverage supply store for residential use. They commonly come in three sizes in the United States: 20lbs, 35lbs, and 50lb tanks for personal use and anywhere from 80lbs-300lbs per tank for commercial use (Airgas, 2019). When full, CO2 cylinders can be heavy and require additional precautions to maneuver. For example, a 20lb tank weighs about 50lbs when full, a 35lb tank weighs about 75lbs when full, and a 50lb steel tank can weigh roughly 150lbs which may be difficult to move safely. In commercial cultivation facilities these tanks are usually large and numerous therefore moving them is not an easy task. The average cost can range between $150 - $200 per cylinder for personal use with refills costing approximately $25 every time. Tanks must be inspected annually and registered with a nationwide safety agency so you might have to show some identification when you purchase a CO2 cylinder from a supplier. When you go to refill your tank, most suppliers will exchange your tank and refill them. Commercial gas suppliers often refill tanks without having to exchange cylinders and in some instances certain companies can handle refill without entering the facility. These extremely large compressed gas cylinders are usually secured with a chain in a secure area away from high traffic and are rarely moved.

Outdoor CO2 Storage

Image of CO2 cylinders located outside of a cultivation facility.

Residential Cultivation Using CO2

It is important to know and understand the properties, uses, and safety precautions before using any gas. Knowing how to store and secure CO2 cylinders will help keep individuals safe from accidents. CO2 cylinders should be stored in a well ventilated area less than 125°F and standing upright (EWU, 2015). In the state of Colorado it is common to see cylinders stored both outside or inside depending on the commercial facility and the preference of the individual in residential settings. CO2 cylinders should also be secured to a wall, preferably with a chain to secure them into place and prevent tipping or falling. In both residential and commercial settings, cylinder caps are commonly used. Cylinder caps perform two functions. First, they protect the valve on the top of the cylinder from damage if it is knocked over. Second, if gas is accidentally released through the valve, the cap will vent the gas out of both sides, minimizing the likelihood that the cylinder will topple. Cylinder caps should not be removed until the cylinder is secured in place and ready for use. In place of Cylinder caps are valve guards which offer the same protection to valves while making the cylinders easier to handle. Plastic guard valves are common on smaller CO2 cylinders weighing less than 100lbs (American Cap Company, 2019).

CO2 Gas Cylinder

Small compressed CO2 gas cylinder with a plastic protective collar, valve, regulator, and flow meter. Including a sensor, this would be an adequate setup for most home growers. Image taken by RMK.

When transporting compressed gas cylinders you should never store a charged cylinder in a passenger vehicle or in the cab of any vehicle as changes in temperature and minor impacts can cause the cylinder valve to rupture. Cylinders should be transported standing on their base or lying on their side in the bed of a truck (Catalina Cylinders, 2015). Never drag or roll a cylinder whether it is empty or not as this can damage the cylinder shell. If a cylinder is too heavy to move, then use a dolly and secure the tank to the dolly and do not try to lift the cylinder by the cap or collar. It is possible for a leak to occur from a compressed gas cylinder. Leaks can occur at the valve, regulator, cylinder stem and at the hose connection so check them regularly and if the cylinder is leaking just set it outside.

Compressed gas cylinders generally require the installation of a valve which is considered the most vulnerable part of a compressed gas cylinder. The valve allows the cylinder to contain gases and allows gas to be filled into or emptied from the cylinder. Open valves slowly by hand to avoid any potential dangers and leave the valve in a position so that the flow of gas can be stopped immediately in an emergency. Using a controller or sensor to monitor CO2 levels and control the flow of CO2 is crucial to accurately apply additional CO2 to your garden without risk. If a controller or sensor is not used, then you have to calculate the volume of your grow space and multiply that number by the amount of CO2 needed in cubic feet. From there you can determine how you will setup your timer settings. There are online CO2 flow rate calculators that will do this work for you and one great example that I use is Hydrofarm’s CO2 Flow Rate Calculator which works great and is simple to use all that you have to do is find out the volume of your grow space in feet.

Flow Rate Calculator

Hydrofarm’s online CO2 Flow Rate Calculator is great and simple to use. It makes it easier to calculate the flow rate and time duration for timer settings. Most importantly is that it is accurate. I personally use this calculator because I use CO2 in my grow tent at home.

Commercial Cultivation with Green CO2

It is imperative that commercial cultivation facilities mark grow rooms and the storage area with proper precautionary signs, such as flammable, oxidizer, or toxic to provide a caution sign for individuals who may enter the facility. Many small commercial grows opt out of purchasing and setting up their own CO2 equipment because of the lack of expertise and disposable revenue at their disposal. Instead, these small commercial cannabis grows choose to have these sorts of services handled through a third-party which is quite common. Green CO2 is one of the most popular companies for indoor cannabis cultivators in the state of Colorado because of their high level of service. They will handle equipment setup and will refill tanks without having to enter any facility. Their proprietary system is great for both small and large cultivation facilities alike and is leased for a fee which can be a more financially appealing option as buying the equipment can be quite expensive for cultivation companies. I have personally seen Green CO2 systems in a majority of commercial cannabis grows that I have worked at or visited and you might have or will see this system if you are ever inside a commercial cultivation facility.

Greenphlow Controller

Greenphlow Controller
Green CO2 will install the emergency monitor device, a high cycle solenoid valve, and a high flow rated regulator all attached to their “greenphlow” controller within commercial grow buildings. Their system is easily expandable if more gas is required and the equipment does not require much a footprint on the wall because it occupies less than three cubic feet for small indoor cultivation facilities. Image by RMK.

Emergency Monitor Device

Emergency Monitor Device (EMD)
The EMD is a sensor that measures and displays the amount of CO2 in the room in parts per million (ppm). If levels of CO2 exceed the safe threshold, then the system can shut off and sound an audible alarm and yellow strobe light to alert individuals of a potential toxic levels of CO2. The regulator is often paired with the emergency monitor device to accurately monitor the level of CO2 which is crucial in cannabis cultivation. Image taken by RMK.

Photo Cell Unit

Photo Cell Unit
The photo cell unit is a light sensor unit that pairs with the EMD and DS6000 differential diverter valve system to turn stop or start the flow of CO2 in order to maximize the use of carbon dioxide in commercial grows.


Using compressed gas cylinders is generally safe, but it is important that they are stored properly, handled correctly, and used with the correct equipment. For residential growers, the purchasing of the proper equipment and knowledge of its proper use is crucial because the onus is on you to handle it safely in your own home. Commercial growers can rent equipment and pay for gas from reputable industrial CO2 providers that handle most of the setup and maintenance of equipment as well as refilling for a fee. Knowledge of the gas contained in the cylinder is important and information can be provided through a Material Safety Data Sheet (MSDS) for individuals who work in an environment where supplemental carbon dioxide is used. You can find an MSDS for carbon dioxide from the University of Maryland’s Division of Information Technology, but you can always get an MSDS directly from the supplier as well.


  1. Catalina Cylinders. (2015). “Storing of CO2 Cylinders”. Catalina Cylinders.

  2. EWU. (2015). “Standard Operating Procedure (SOP) Compressed Gas Cylinders”. Revision 2. Eastern Washington University.

  3. Green CO2. (2015). “Indoor Cultivation Facilities”. Green CO2 Systems.

  4. Virtra. (2014). “CO2 Safety And Operations Manual: Guidelines For Safely Handling CO2 Based VirTra Products”. VirTra.

  5. American Cap Company (2019). “Valve Protection”. American Cap Company.

  6. Airgas (2019). “Industrial Grade Carbon Dioxide Cylinders”. Airgas.

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