The Ultimate CO2 Guide for Indoor Growing

CO2 Management for Indoor Cultivation

CO2 plays a key role in plant photosynthesis, nutrient uptake, and overall plant health. Maintaining appropriate CO2 levels in your grow space can boost your yield significantly and help you avoid many pest and environmental issues.

Gaining expertise in CO2 management can make you the master of your growing environment, significantly improving your outcomes.

Quick Summary

  • Successful CO2 management can boost yield and prevent pest and environmental issues in the grow space.
  • The photosynthesis process requires a careful balance of CO2 with light, temperature, humidity, and Vapor Pressure Deficit (VPD).
  • Different supplementation techniques include CO2 burners, tanks, bags, fermentation, and CO2 pads, each with unique pros and cons.
  • Safety measures must be in place when dealing with CO2, especially in larger grow rooms, as excessive levels can be harmful.
  • Optimal CO2 levels vary across different plant growth stages: 600-1200 PPM for seedlings, 800-1500 PPM for vegetative and flowering/blooming stages, and 400-800 PPM during the final weeks of flowering.
  • CO2 supplementation is unnecessary during night hours as photosynthesis ceases and plant metabolism is dominated by respiration.


Ready to implement CO2 supplementation? Here's a step-by-step guide.

Take the guesswork out of CO2

Table of Contents


Indoor cultivation has become increasingly popular due to its numerous benefits, such as controlled growing conditions, year-round harvests, and the ability to produce high-quality, potent plants.

In this article, we will explore the role of CO2 in indoor cultivation, its benefits and risks, methods for CO2 supplementation, and how to determine the ideal CO2 concentration for your plants.

Why is CO2 Important?

Photosynthesis Cycle Diagram
Photosynthesis Cycle Diagram


To appreciate the significance of CO2 in indoor cannabis cultivation, it's crucial to understand the process of photosynthesis and how it relates to plant growth. Photosynthesis is the process through which plants convert light energy into chemical energy to fuel their growth. During photosynthesis, plants absorb CO2 from the air and combine it with water and light energy to produce glucose (sugar) and oxygen. Glucose provides energy for growth and development, while oxygen is released back into the atmosphere.

CO2 is a critical component in the photosynthesis process. It is the primary source of carbon used by plants to synthesize organic compounds needed for growth and development. Inadequate (and excessive) CO2 levels can limit photosynthesis and reduce overall plant growth.

Getting the CO2 Balance Right

Managing CO2 in an indoor garden is not just about adding more of it. It requires careful balancing with other environmental factors like light, temperature, humidity, and VPD.

  • Light: The relationship between CO2 and light is relatively direct; more CO2 allows for more intensive photosynthesis under higher light conditions. So when you add CO2, make sure your plants get enough light.

Interactions of Light, CO2 and Temperature on Photosynthesis

  • Temperature: Higher levels of CO2 increase the ideal temperature for photosynthesis
  • Humidity: Humidity levels can impact VPD, and thus how efficiently plants absorb CO2. Both low and high humidity can interfere with CO2 intake, so use VPD as a guide and aim for a balanced humidity level.
Impact of ideal VPD on Tomato Plant Dry Weight
Impact of ideal VPD on Tomato Plant Dry Weight (doi:10.1038/s41598-019-45232-w)
  • VPD: Vapor Pressure Deficit (VPD) and Carbon Dioxide (CO2) work in synergy to optimize plant growth: CO2 fuels the photosynthesis process while VPD regulates the plant's transpiration rates, balancing water loss with CO2 absorption.

CO2 Supplementation Techniques

1. CO2 Burners:

co2 burnerCO2 Burner

CO2 burners, also known as generators, are machines that burn propane or natural gas to produce CO2.


  • They can produce a high quantity of CO2, making them suitable for larger operations.
  • Burners can be regulated, providing more control over CO2 levels.


  • They can increase heat and humidity, which could harm plants if not carefully controlled.
  • They can be expensive to run, depending on the cost of propane or natural gas.
  • They require adequate ventilation to avoid the accumulation of harmful by-products such as nitrogen oxides.

2. CO2 Tanks:


co2 tankCO2 Tank


CO2 tanks, often used in beverage dispensing or paintball, store CO2 under high pressure.


  • They provide a clean and pure source of CO2.
  • They are portable and do not increase heat or humidity.


  • They can be expensive and require regular refills.
  • Regulating the output can be a bit more complicated, often requiring a regulator, solenoid, and timer.

3. CO2 Bags:


co2 bag

CO2 Bag


CO2 bags contain fungi or other microbes that produce CO2 as a byproduct of their metabolism.


  • They are simple to use, needing only to be opened and placed in the growing area.
  • They are relatively cheap and require no electricity.


  • They produce a relatively small amount of CO2, so are only suitable for small-scale operations.
  • The rate of CO2 production cannot be regulated, and it depends on the metabolism of the microbes, which can vary based on temperature and other factors.

4. Fermentation:


yeast fermentation

Yeast Fermentation


Some growers use natural fermentation processes (sugar and yeast) to produce CO2.


  • It's an inexpensive method and easy to set up.
  • This process does not require electricity.


  • Similar to CO2 bags, the amount of CO2 produced cannot be precisely controlled.
  • It can produce unpleasant odors and requires regular maintenance.
  • Like bags, this method is typically suitable for smaller grow spaces.

5. CO2 Pads:

 co2 pads

CO2 Pads

CO2 pads are similar to bags, but they are soaked with a solution that releases CO2 when water is added.


  • They're quite easy to use.
  • CO2 pads are relatively inexpensive and don't need electricity.


  • It's challenging to control the rate of CO2 release.
  • Like bags and fermentation, pads are only ideal for smaller areas.

Remember, the suitable method for your specific situation will depend on the size of your grow area, your budget, and your ability to control the growing environment (temperature, humidity, etc.). It's crucial to remember that while CO2 is beneficial for plants, excessive levels can be harmful to humans and pets. Therefore, having adequate ventilation and CO2 monitors with alarms in larger grow rooms is crucial for safety.

Safety Measures When Dealing with CO2


co2 alarm

CO2 Alarm


While CO2 is essential for plant health, concentrations above 5000ppm are considered to be harmful to humans and animals. Always ensure adequate ventilation in your indoor gardening area. CO2 monitors with alarms and automated ventilation are also recommended for larger grow rooms to alert you when CO2 levels exceed safe limits.

Ideal CO2 levels for different plant growth stages


CO2 Monitoring With Pulse Pro

CO2 Monitoring With Pulse Pro



  • Seedling Stage: It may not be common knowledge, but even seedlings benefit from CO2 supplementation. Maintaining CO2 levels between 600-1200 PPM can increase root growth and plant development, especially with higher light levels. [source]
  • Vegetative Stage: As the plant matures and the photosynthesis process becomes more robust, raising CO2 levels to around 800-1500 PPM can support faster and healthier growth.
  • Flowering/Blooming Stage: CO2 levels can be maintained at the same range as the vegetative stage, i.e., around 800-1500 PPM. However, careful monitoring is needed as higher CO2 levels can sometimes lead to higher temperatures which can be detrimental for the flowering process.
  • Final Weeks of Flowering: During the last couple of weeks of the flowering phase, it's usually recommended to lower CO2 levels back down to around 400-800 PPM. This helps to ensure the plant isn't taking in too much CO2, which could potentially affect the quality of the flowers or fruit.

Remember, these are general guidelines and optimal CO2 levels may vary depending on the specific plant species, overall health of the plants, and other environmental conditions such as light, temperature, and humidity.

How Much CO2 is Needed For Your Grow Space

The amount of CO2 needed for supplementation depends on several factors, including the size of the grow space, the desired concentration of CO2, and the ventilation rate. Here is a general process to estimate the amount of CO2 needed for supplementation:

  • Calculate the volume of your grow space:
  • The volume of a room can be calculated using the formula:

    Volume = length x width x height

    Make sure all measurements are in the same units, typically meters or feet.

  • Choose the desired CO2 concentration:
  • For most plants, a CO2 concentration of around 1200-1500 parts per million (ppm) is beneficial. Be sure to adjust based on the specific needs of your plants.

  • Convert the desired concentration to a proportion of the air volume:
  • CO2 concentration is often given in ppm, but for this calculation, it's helpful to convert it to a proportion of the total air volume. There are a million parts in a total, so a concentration of 1200 ppm is 1200/1,000,000 = 0.0012.

  • Calculate the amount of CO2 needed to achieve the desired concentration:
  • Multiply the volume of your grow room by the desired CO2 proportion to get the volume of CO2 needed:

    Volume of CO2 needed = Volume of the room x desired CO2 proportion

    This gives you the amount of CO2 needed to reach your desired concentration, assuming a completely sealed room.

  • Adjust for ventilation:
  • If your grow room is ventilated, then CO2 will be lost and needs to be replaced. You can estimate the amount of air exchanged per hour based on your ventilation system and multiply this by the desired CO2 proportion to get the amount of CO2 to add per hour.

    Please note that this calculation assumes perfect mixing of CO2 in the air, which may not be the case in reality. It's a good idea to monitor CO2 levels regularly with a CO2 meter to ensure you're hitting your desired concentration.

    Grow Room CO2 Supplementation Calculator

    Enter the dimensions of your grow space, the current and desired CO2 concentration, and your air exchange rate:

    Current CO2 concentration (ppm):
    Desired CO2 concentration (ppm):
    Air exchange rate (minutes):

    Unit of measurement:



    Monitoring CO2

    Dual Channel NDIR CO2 Sensor in the Pulse Pro
    Dual Channel NDIR CO2 Sensor in the Pulse Pro


    Achieving reliable and accurate CO2 measurements is crucial for optimal plant growth, leading to improved results and cost savings. By utilizing advanced sensor types and leveraging connectivity options, CO2 monitors like the Pulse Pro offer the most effective way to monitor and control CO2 levels.

    • Sensor Types:

      • Non-dispersive infrared (NDIR) sensors: Most common and accurate type, measure CO2 levels based on light absorption.
      • Chemical sensors: Use a chemical reaction to detect CO2 levels, suitable for portable or low-cost applications.
      • Solid-state sensors: Utilize a solid material that reacts to CO2, offering durability and low power consumption.
    • Connectivity Options:

      • Wireless connectivity: Enables real-time monitoring and remote access to CO2 data.
      • Data logging: Stores historical CO2 measurements for analysis and trend identification.
      • Alerts and notifications: Sends notifications when CO2 levels deviate from the desired range.
      • Integration with control systems: Seamless coordination with ventilation or CO2 supplementation systems.

    Reliable and accurate measurement of CO2 levels is essential for optimal plant growth. CO2 monitors equipped with advanced sensor types, such as non-dispersive infrared (NDIR) sensors, provide the most reliable and accurate readings. By leveraging connectivity options, growers can access real-time data, analyze historical trends, and receive alerts when CO2 levels fluctuate. This leads to better results and cost savings by enabling precise CO2 adjustments and ensuring a healthy and productive indoor environment for plants.


    Step by Step: How to Implement CO2 Supplementation For Your Grow

          1. Plan:

            1. Determine the CO2 requirements: Research the CO2 requirements of the plants you are growing and determine the optimal CO2 level for their growth stage.

            2. Calculate the room volume: Measure the dimensions of your grow room and calculate its total volume.

            3. Assess ventilation: Evaluate the current ventilation system in your grow room to ensure efficient distribution of CO2.

          2. Prepare:

            1. Choose a CO2 supplementation method: Decide on the CO2 supplementation method based on your budget, room size, and personal preferences. Common methods include CO2 generators, compressed CO2 tanks, or CO2 bags.

            2. Seal the grow room: Ensure the room is properly sealed to minimize the loss of CO2. Check for any gaps, leaks, or openings where CO2 can escape. Use weather stripping, caulk, or other suitable materials to seal doors, windows, vents, and any other potential areas of air leakage.

            3. Set up equipment: Install the CO2 supplementation equipment in a suitable location within the grow room, following the manufacturer's instructions.

            4. Establish safety measures: Familiarize yourself with safety guidelines related to CO2 supplementation, such as proper ventilation, monitoring equipment, and emergency procedures.

          3. Implement:

            1. Monitor CO2 levels: Use a CO2 monitor or controller to regularly measure and maintain the desired CO2 level in the grow room. Set the controller to the appropriate CO2 concentration.

            2. Set timers: Program timers or controllers to regulate the CO2 supplementation schedule, ensuring plants receive CO2 during daylight hours when photosynthesis is most active.

            3. Adjust ventilation: Fine-tune the ventilation system to maintain an optimal CO2 concentration. Ensure the fresh air intake does not dilute the CO2 levels too much.

          4. Monitor:

            1. Regularly check equipment: Periodically inspect the CO2 supplementation equipment to ensure proper functioning, adequate gas supply (if applicable), and no leaks or malfunctions.

            2. Monitor plant health: Observe plant growth, development, and overall health to assess the effectiveness of CO2 supplementation. Look for signs of improved growth, increased yields, or any adverse effects.

            3. Track CO2 levels: Continuously monitor CO2 levels using a monitor or controller to ensure they remain within the desired range.

            4. Stay accurate: Make sure to calibrate your sensors intermittently to maintain accurate measurements.

          5. Adjust and optimize:

            1. Fine-tune CO2 levels: Based on plant response and monitoring data, adjust the CO2 supplementation levels if necessary. Some plants may require higher or lower concentrations during different growth stages.

            2. Optimize timing: Experiment with different timing schedules to find the most effective CO2 supplementation period for your plants.

            3. Seek expert advice: If you encounter challenges or want to optimize your CO2 supplementation further, consult experienced growers or horticultural specialists for advice and guidance.

    CO2 at Night

    At night, photosynthesis ceases since there is no more light and plants' metabolism is dominated by respiration. Respiration converts oxygen (O2) to CO2. Hence, CO2 supplementation is not necessary during these hours. To conserve CO2 and energy, it is recommended to stop CO2 supplementation during the dark periods.


    CO2 management is a pivotal aspect of indoor gardening success. By understanding and balancing CO2's role with other vital factors like light, temperature, and humidity, indoor gardeners can achieve remarkable growth and yield. This is not without challenges, but the right knowledge and equipment can make all the difference. The future of indoor gardening looks bright with the promise of CO2 optimization.

    Further Reading

            1. Taiz, L., Zeiger, E., Møller, I. M., & Murphy, A. (2015). Plant Physiology and Development (6th ed.). Sinauer Associates. Chapter 7: Photosynthesis: Using Light to Make Food

            2. Idso, S. B., & Kimball, B. A. (2002). CO2 enrichment of sour orange trees: 13 years and counting. Environmental and Experimental Botany, 48(2), 97-109.

            3. Körner, C., Asshoff, R., Bignucolo, O., Hättenschwiler, S., Keel, S. G., Peláez-Riedl, S., ... & Zimmermann, S. (2005). Carbon flux and growth in mature deciduous forest trees exposed to elevated CO2. Science, 309(5739), 1360-1362. DOI: 10.1126/science.1113977

            4. Bloom, A. J., Asensio, J. S., Randall, L., & Rachmilevitch, S. (2012). Carbon dioxide enrichment inhibits nitrate assimilation in wheat and Arabidopsis. Science, 328(5980), 899-903. DOI: 10.1126/science.1186440

            5. USDA National Agricultural Library. (2021). CO2 and Plants: The Impact of Carbon Dioxide on Plant Growth.

            6. "The Future of Greening the Earth's Biosphere." CO2 Science, Web.



    Take the guesswork out of CO2

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