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What is CO2 Enrichment?

greenhouse co2 enrichment

CO2 enrichment is the process of increasing the amount of carbon dioxide to a level higher than what is normally in fresh air.

Higher levels of CO2 than normal in air can be caused by human or animal respiration in an enclosed area, by natural off-gassing of CO2 from the ground, or by combustion or compressed CO2 gas.

What makes CO2 enrichment unique is that it is purposely done by indoor growers or in greenhouses to increase plant growth, flowering and to speed the time to harvest.

What is meant by CO2 enrichment?

Fresh air typically contains approximately 400-450 ppm (parts per million) or 0.04% carbon dioxide by volume. Raising the CO2 level to anything above this is considered CO2 enrichment.

How do you enrich CO2?

Air can be enriched with CO2 naturally or artificially.


Humans and animal respiration is the process of taking in oxygen and breathing out CO2. If they are in an enclosed area like a car or a room, after a few minutes the CO2 in their breath will cause the carbon dioxide levels to rise relative to the oxygen level.


When CO2 from the soil leaves the ground, it naturally mixes with the air. Because CO2 is heavier than air, in extreme circumstances the CO2 can pool in a tunnel, hole or valley and create a pocket of potentially dangerous levels of CO2.

Artificial Enrichment

Plant growers can artificially increase the CO2 level in indoor greenhouses or grow rooms by adding CO2 from compressed tanks or cylinders of the gas. In small grow rooms, this can be accomplished by adding bags of organic matter or fermenting buckets that continuously off-gas CO2. Large commercial greenhouses may use CO2 generators or natural gas burners that give off CO2 as a byproduct of combustion.

Can CO2 enrichment be beneficial to plant growth?

All other factors being the same, plants will grow faster as the CO2 level increases. Plants grow naturally at 400ppm (0.04% by volume) of CO2. Research shows that doubling or tripling the amount of CO2 (800-1,200ppm) available to plants during the daylight growing cycle will increase growth 40-100% depending on the plant species.

However, as additional CO2 is added beyond about 1,200ppm the benefits decrease. Increasing the CO2 level to 4x or 5x normal will result in little to no change. At 2,000ppm and above, too much CO2 may cause plant damage.

How do I increase CO2 in my grow tent?

The three most common methods of increasing the level of CO2 in a grow tent are

  • Fermentation buckets
  • CO2 bags
  • Piping in CO2 from compressed gas cylinders.

The advantages of fermentation buckets, decomposing organic matter or CO2 bags is that they are inexpensive. The disadvantage is that over time they lose effectiveness and must be replaced or replenished. In addition, you cannot regulate the exact amount of CO2 being delivered to your plants beyond adding more bags or buckets. However, given their low cost many new growers start with CO2 bags or buckets and a low-cost CO2 monitor.

For many modern growers, tanks of compressed CO2 gas are a preferred option. While the initial start-up cost can be a few hundred dollars for the CO2 controller, tank, regulator, and distribution tubes.

Does adding CO2 increase yield?

There are many benefits to increasing CO2 beyond yield.

  • Increased growth and plant size.
  • Plants mature faster resulting in faster harvests.
  • Faster maturity saves energy and fertilization costs per harvest.
  • Increase in the number and size of flowers.
  • Reduction in transpiration and increases water use efficiency.

For more information, see all our CO2 meters and monitors for agricultural use.

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