How to ventilate a mushroom grow room?

The choice of ventilation system depends, first of all, on the climate in your region and the method of arranging bags or briquettes with the substrate.

The oyster mushroom growing system also has a significant influence.

To some extent, the choice of ventilation system may also be influenced by the composition of the substrate. I will describe the details in this article.

The content of the article:

  1. How much fresh air for oyster mushrooms?
  2.  Air exchange using an exhaust fan is passive-active ventilation.
  3. The blower fan is used with different types of exhaust ventilation.
  4. When a ventilation system with recirculation is required.

How much fresh air for oyster mushrooms?

The amount of fresh air directly depends on the number of growing mushrooms in the growing room.

Do oyster mushrooms need fresh air?

Many mushroom growers misunderstand the reason for the need for outside air. Oyster mushrooms have enough oxygen to breathe.

Fresh air is needed to replace the air inside the grow room, mainly to remove excess levels of carbon dioxide.

That is why it is not so much the quantity of air that is important to us, but rather the correct air exchange at a certain flow rate. The air flow carries carbon dioxide away from the growing oyster mushroom clusters. Therefore, this flow must be constant, that is, ventilation must work 24 hours a day.
Read also my articles:
- about CO2 levels
- about air exchange

Air exchange using an exhaust fan

Passive-active ventilation is such ventilation when air passively, that is, by itself, enters the room for the reason that the exhaust fan forcibly (that is, actively) removes air from the room.

Passive-active ventilation

In what cases can this type of ventilation be used?

mushroom blocks on the floor1. When mushroom blocks stand only on the floor, or rectangular briquettes with substrate stand on top of each other in height, no more than 1.2-1.3 meters.
The height of the room must be at least 3 meters.

See here for placement without shelving.

Such a system is called Tornado - axial fans are placed under the ceiling in the premises, which accelerate and mix the flows, perfectly removing CO2.
One or more axial fans are placed below to provide exhaust.

During the warm season, evaporative panels are inserted into the air holes to cool and humidify the air.

2. When the climate in your region is warm enough, and during the cold period the temperature does not drop below 3-5 degrees below zero at night.

3. When there are hot and dry(usual humidity does not exceed 50-55%, and often even lower) periods of the year as additional ventilation for these periods.

The distance from the holes in the wall to the exhaust fans should not exceed 8-10 meters, otherwise the flow speed will drop significantly.

Disadvantages of passive-active ventilation:

1. The air flow is often uneven, so there are places in the room where the mushrooms have an unsightly shape.
How to fix? Additional axial fans are located under the ceiling in some places in the room.

2. Difficulties arise with heating and humidifying the incoming outdoor air.

How to fix?

Units for heating and humidifying the air are located near the holes. However, this may lead to losses in flow rate. Therefore, additional fans may be needed.

Another way to heat and humidity the air is to build a long corridor near a wall with holes. Then a large hole is made in the corridor, near which a heat exchanger is installed and a humidifier is located further along the corridor. Accordingly, warmed and humidified air from the corridor enters the room.

Active type of ventilation

Forced air intake into the oyster mushroom growing room using a fan is used much more often.

Air removal can be either active, using exhaust fans, or passive, using gravity shutters.

The active-passive type of ventilation is also used in the production of button mushrooms.

You can read more about this type of ventilation in my article.

This type of ventilation is the most unified - you can buy a ready-made unit with heating and humidification of the driving air, which is designed for a certain number of tons of substrate, or you can make such a unit yourself, using a blower fan, a heat exchanger and a humidifier.

Also, automated climate control systems in mushroom rooms have been developed for this type of ventilation.

Many devices that control temperature and humidity in poultry incubators are also suitable for controlling the microclimate system in an oyster mushroom room.

If the climate in your area is warm enough and does not have sharp changes in night and day temperatures, only fresh air can be supplied to the growing room.

In all other cases, a ventilation system with air recirculation from the growing room is used.

When a ventilation system with recirculation is required


1. If you have a single zone growing system, no incubators.

In this case, you need a recirculation system no matter what your climate is.

You can read more about the single-zone system here. You bring the mushroom blocks you just made into the room and set the incubation mode.

recirculation system

The ventilation system can be turned off for the first 4-5 days. When the blocks begin to warm up, you turn on the ventilation to 100% recirculation mode.

If the heating is higher than 33 degrees Celsius in the center of the block, you connect the cooler or turn on the split system. And the ventilation system continues to operate in the same mode.

As the mycelium grows, you introduce some fresh air, maintaining the carbon dioxide level according to the incubation schedule.

At the moment of the most intense fruiting of mushrooms on the first flush, you use from 60 to 80% of fresh air, and on the second harvest, you can open the fresh air damper by only 40-50%.

2. If the climate in your region has sharp changes in day/night temperature and humidity, and also if you have a long period of frost and/or heat.

In this case, you need a recirculation system regardless of what kind of oyster mushroom growing system you have - with or without incubators.

You mix room air, which has the required humidity and temperature, with fresh air that needs to be humidified and warmed (or cooled). This way you save electricity and prevent sudden changes in microclimatic parameters in the growing room.

Oyster mushroom can grow at temperatures and humidity that are not very comfortable for it, but it really does not like sudden changes in a short period of time.


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