co2 ppm for cannabis

How to increase the carbon dioxide concentration for cannabis?

Growpackage Eco Farm
Nov 28, 2019 · 6 min read

How to use CO2 in cannabis grows is one of the many questions that we’re frequently asked. CO2 is essential for cannabis plants and every other plant, as to them CO2 is like oxygen and they need it to survive. Cannabis plants can deal with CO2 levels of up to 600% the amount that there naturally is in the air around us. Basically, it makes their cells multiply much faster, so if you use extra CO2 during the flowering period you’ll get buds that are much thicker than usual which, if done correctly, makes for a much bigger yield.

I f you don’t use CO2 in the right way you could end up with yellowing plants, or long stretched out plants with hardly any buds. You’re going to need to know what you’re doing to implement CO2 correctly. There are many systems that can be used to get more CO2 into your crop; beginner systems that are used as a little extra boost and don’t require much care, and then professional systems that measure the PPM of CO2 that there is in the atmosphere. Professional systems are obviously much more effective and efficient than beginner ones, but they also require more work and attention.

You can use any way of dispensing CO2, connected to a CO2 controller that will shut off the flow of CO2 once it reaches a certain level, and open it again once it gets too low. If all you have is a normal CO2 meter, you can still control the CO2 levels by opening and closing a solenoid valve using a timer. (Solenoid valves are valves that are opened and closed with an electromagnetic charge). Whichever kind of system you use, you must know the exact PPM (parts per million) of CO2 in your grow room.

CO2 needs to be introduced into your room through a silicone tube, with one outlet per plant near the bottom of the trunk. You can also use a 2m tube to go around the grow area with holes facing the center, towards the plants.

Once everything’s installed and ready to go, you’ll need to know exactly how to use CO2. Well, it’s used in the flowering period from the 21st day onwards, once the buds start to take shape and are slowly popping up at the tips of all of the branches. You’ll need to change your air filtration so that the extractor only works for around 15 minutes an hour because if it’s left on it will get rid of all of the CO2 and all of the effort will have been for nothing. You can use another timer to program the CO2 controller so that it doesn’t turn on when the extractor is on. CO2 should only be administered when the lights are on, as the extraction should be on constantly when the lights are off.

CO2 increases your plants cell walls and multiplies them rapidly, but make sure that you fertilize them also as they’ll end up light and pretty down looking if they get a lot of CO2 but not any nutrition. They’ll also need a slightly higher heat than usual, around 28–32ºC so that the water in the leaves can evaporate slightly faster and the plants can absorb the nutrients straight away. Basically, we want the plants to absorb the nutrients but get rid of the water fast. You’ll need a dehumidifier to lower the ambient humidity to normal levels, because once the temp is raised and your plants begin evaporating water, humidity levels will raise a lot.

Pros and Cons of Using CO2 for Growing Cannabis

Benefits of Adding Extra CO2

  • Bigger Yields, Faster Growth — If you’ve maxed out the other limiting factors (especially light), CO2 can make your plants grow up to 20% faster, produce bigger plants, and enhance your yields.
  • Higher Temperature is Okay — Maintaining 1200–1500 PPM of CO2 in the grow area allows growers to keep temperatures much higher than normal, up to 95°F (30°C). For growers with hot bright lights, this can make it easier to keep temps at a range their plants will like.
  • Security — CO2 enrichment can be beneficial for security if you seal your grow room since you’re not venting out smelly air. Certain methods of adding CO2 like using a CO2 generator will also create natural smells that help cover up the smell of cannabis directly.

Disadvantages of Adding Extra CO2

  • Not As Effective If You Don’t Have Bright Grow Lights — As far as light intensity is concerned, you probably need either MH/HPS grow light or strong LED grow lights to produce bright enough light for your plant to be able to use the extra CO2. CFLs and T5s probably aren’t bright enough to get great results with CO2.
  • May Need to Seal the Grow Area — Although adding just a little CO2 doesn’t require a sealed room, when trying to maintain very high levels of CO2 (like 1200–1500 PPM) you probably need to seal up grow area so it’s airtight in order to prevent CO2 from leaking out.
  • Cost of Adding Extra CO2 — It can be expensive to get started if you want to inject a whole lot of CO2 into your grow area, for example in big grow operations. The cheapest ways to add CO2 are actually not very good at providing a lot of CO2 over time, but can be a great way to “dip your feet” and try CO2 out. The best CO2 setups in the long run are a bit more pricey to get started with, though they become a lot cheaper once you’ve got your initial supplies.


Once you’re confident you have decent grow experience and a professional set up, you’re ready to try increasing your yields with added CO₂.

Remember, for best results you’ll want to invest in a quality kit that allows you to measure the ppm (parts per million) of the CO₂ in your grow space. Without an exact idea of how much CO₂ is in the atmosphere, it is virtually impossible to measure whether your plants are getting the right amount of exposure.

CO₂ levels in our atmosphere average around 400ppm. The ideal CO₂ levels to increase the yield of cannabis plants is roughly 1,200 to 2,000ppm. Studies show that CO₂ levels of up to 10,000ppm can still significantly increase plant growth. However, managing a grow space with such high concentrations of CO₂ is difficult as CO₂ levels over 3,000ppm are dangerous to humans, and concentrations of roughly 5,000ppm are considered lethal.

The two most popular ways of introducing extra CO₂ to your cannabis grow include using CO₂ generators or tanks (which we will explore in a bit more detail later).

Ideally, extra CO₂ should enter your garden from above. The gas is heavier than oxygen, so it will naturally sink to the floor. You should also use fans or a ventilation system to ensure the CO₂ is spread evenly across the room.

Remember to introduce your extra CO₂ gradually and to keep a close eye on how your plants respond. You’ll also want to increase your light sources and temperatures (to roughly 29–32°C or 85–90°F) or your plants will get damaged.

Excess CO₂ should always be added to your garden when the lights are on and your plants are photosynthesizing.

The two most popular ways to add extra CO₂ to your cannabis grow area rely on CO₂ generators or tanks.

CO₂ Generators: CO₂ Generators look similar to patio heaters and burn propane or other natural gases in order to produce carbon dioxide. It’s important to note that they produce extra heat, which can be hard to regulate, especially in small areas.

CO₂ Tanks: CO₂ tanks contain compressed carbon dioxide that can be readily released into the atmosphere. They are ideal for smaller grow ops or for growers who don’t want the extra hassle of producing their own CO₂ with a generator.

To ensure you get the best results from your CO₂, you’ll want to make sure you’re able to easily and accurately measure the carbon dioxide levels in your grow area.

The easiest way to do this is to invest in a CO₂ meter. The most basic models start at about €110.

Indoor growing is becoming more and more popular for a variety of reasons, including legal issues and space constraints. Whatever the reason, if you’re looking to max out the potential of your indoor plants, we highly suggest experimenting with CO₂ levels.

How to use CO2 in cannabis grows is one of the many questions that we’re frequently asked. CO2 is essential for cannabis plants and every other plant, as to them CO2 is like oxygen and they need it…