How to Optimize CO2 Levels for Mushroom Cultivation

Did you know that ensuring proper ventilation is crucial for the success of your mushroom cultivation? Ventilation plays a significant role in renewing the air inside your growing space with fresh air from outside. By doing so, it helps eliminate excess CO2 and other gases like oxygen and ethylene that can adversely affect mushroom growth. Moreover, ventilation allows you to regulate temperature and humidity, which are key factors for optimal mushroom development. In this article, we will explore simple and effective ways to control CO2 levels in your grow room.

The Impact of Carbon Dioxide on Mushroom Growth

Mushrooms do not perform photosynthesis like plants, but they still require CO2 for their metabolism. However, too much CO2 can be detrimental to their growth and quality. High levels of CO2 can cause several problems, including reduced fruiting, reduced size, reduced potency, and altered flavor and aroma.

How to Control CO2 Levels in a Grow Room

how to control co2 in mushroom grow room

There are two main ways to control CO2 levels in a grow room: ventilation and supplementation.


Ventilation involves exchanging the air inside the grow room with fresh air from the outside. This process helps remove excess CO2 and other gases that can affect mushroom growth. It also helps regulate temperature and humidity in the grow room. Ventilation can be achieved using fans, ducts, filters, and vents. The frequency and duration of ventilation depend on various factors, such as the size of your growing space and specific conditions.

Passive Ventilation

Passive ventilation is a simple and cost-effective method. It involves using a fan to extract air from the growing space, creating a vacuum that draws fresh air through openings or slits.

Advantages: Simplicity and affordability.
Disadvantages: Inadequate airflow for large or crowded spaces.

Active Ventilation

Active ventilation is a more effective and accurate method. It involves using two fans: one to extract air from the growing space and another to introduce fresh air. The fans are connected by ducts with filters to prevent contamination.

Advantages: Greater effectiveness and accuracy.
Disadvantages: Requires more equipment and maintenance.

How to Properly Ventilate Your Grow Room

To ventilate your grow room effectively, follow these steps:

  1. Choose a suitable location for your grow room with access to fresh air and electricity. Avoid places that are too hot, cold, damp, or dusty.
  2. Decide whether you want to use passive or active intake based on your grow room size, mushroom quantity, and budget.
  3. Install a fan on one side of your grow room to blow air out. The fan should create negative pressure to remove stale air quickly. You can use an inline fan, exhaust fan, or box fan.
  4. Install a vent or duct on the opposite side of your grow room to allow fresh air in. The vent or duct should provide adequate airflow and prevent back pressure.
  5. If using passive intake, ensure there are no obstructions or leaks in the vent or duct.
  6. If using active intake, install another fan to blow air in. This fan should be slightly less powerful than the one blowing air out to maintain negative pressure. Additionally, install filters on both ends of the duct to prevent contaminants.
  7. Use a timer or controller to regulate your fans’ operation based on your desired schedule and CO2 levels.
  8. Regularly monitor and adjust your ventilation system to maintain optimal conditions for mushroom growth.

Tips to Ventilate Your Crop

Consider the following tips:

  • Avoid direct sunlight or strong winds as they can damage your mushrooms and cause temperature fluctuations.
  • Place your fans at an appropriate distance from your mushrooms to avoid drying them out or causing physical damage.
  • Choose fans that are not excessively noisy or prone to vibrations to prevent mushroom stress.
  • Clean your fans, filters, ducts, and vents regularly to prevent dust buildup or mold growth.
  • Replace worn-out or broken fans, filters, ducts, and vents.


Supplementation involves adding extra CO2 to enhance mushroom growth. This method can benefit certain types of mushrooms, such as oyster mushrooms, which thrive in higher CO2 levels. Various CO2 sources can be used for supplementation, including compressed gas cylinders, dry ice, fermentation, and burning fuels. However, supplementation requires careful monitoring and regulation to prevent harming both mushrooms and humans.


CO2 is essential for mushroom growth, but it must be carefully controlled in a grow room. Proper ventilation and supplementation are two methods to control CO2 levels. Ventilation helps remove excess CO2 and other gases, while supplementation adds extra CO2 to promote mushroom growth. Remember to closely monitor and regulate CO2 levels to optimize mushroom production. With these techniques, you can create the ideal environment for healthy and thriving mushrooms in your grow room.