Coltivazione: Aspirazione e ventilazione indoor, come scegliere e posizionare. -

Air treatment, extraction, ventilation, temperature and humidity.

The three fundamental elements for life are air, water and light.

This article delves into the role of air in cultivation, a critical element for obtaining good results in terms of quality and quantity.

The right exchange of air is necessary to complete your work and manage ideal conditions for your plants. Let's see how and why.

What does a plant breathe and how does it breathe?

Just as humans and plants breathe, understanding the functioning and dynamics of plant respiration will help you avoid making mistakes when managing your grow room.

Plants cannot develop in environments with poor ventilation, especially intended as air exchange. The means by which plants carry out this important process are their leaves, stems and roots. Aerobic respiration in plants is defined as the process in which oxygen acts as an oxidant.

There are two distinct phases of plant respiration:

Photorespiration in the presence of light

Breathing in the dark regardless of light

Like human beings, plants breathe constantly, however distinguishing 2 different phases, the first which generates photosynthesis and the second which occurs while this process is interrupted.

During the day or inside the cultivation chambers during the light phase, plants have a higher respiratory capacity due to the amount of processes carried out. The temperature of the grow room should always be lower during the night (dark) hours than during the day. It is necessary that the exchange surfaces, such as the roots, have the possibility of constant oxygenation, which is why a substrate that allows good transpiration is important. When using an organic substrate, its oxygenation is even more important in order to allow the fauna present to survive. The substrate must be light and porous in order to allow adequate oxygenation, an excellent method is to add elements such as coconut fibre, perlite or expanded clay to the substrate.

The respiration of plants occurs through the stomata, the nostrils of the plants, through which carbon dioxide is absorbed and oxygen is released.

To prevent the stomata from becoming clogged, an effective method is to spray water at 20-25° above and below the leaves in order to eliminate dust and microdebris that can accumulate; this operation should be carried out 1 or 2 times a month.

In outdoor cultivation this process is carried out by rain.

As is known, plants absorb carbon dioxide and release oxygen during the light phase, reversing the process at night (dark phase). In fact, it is good practice to never place plants in places where you sleep as they could cause harm to humans by releasing carbon dioxide.

Given these simple premises, it is necessary to understand how to manage the ventilation inside the cultivation rooms. How to position fans and air extractors to allow perfect and homogeneous distribution as well as concentration of essential elements.

Why is it necessary to change the air in grow rooms?

Inside a cultivation room it is necessary to create an environment that can guarantee correct air exchange and maintain ideal conditions constant in every area of ​​the available space

In this equation the elements to take into account are temperature, humidity, CO2/oxygen concentration.

By correctly positioning the tools available you will obtain a better result, simple rules that allow your cultivation room to be a perfect and high-performance machine.

Starting from basic assumptions, such as that hot air tends to rise and cold air tends to fall, the ideal position for air extraction is at the top just as the entry of fresh air must be positioned at the bottom, the fans should allow the air to be mixed and made homogeneous, therefore they should be positioned in specific areas with respect to the dynamics of the air flow of the cultivation chamber. By way of example, if we had the extractor and aspirator positioned opposite each other on the side of the room, creating an exiting air corridor only in that area, the fan would have to be positioned so as to push the flow towards the other wall, breaking the corridor and forming different flows inside the grow room which will help make the air more homogeneous.

These measures will avoid the formation of mold and parasites with consequent weakening of the plants, instead guaranteeing a perfect environment and an excellent result.

Which tools to use for air exchange?

Tools needed for air management are:

In addition or replacement and for caution

  • Soundproof extractor and aspirator or soundproof box
  • Odor filter
  • Soundproof ducts


Necessary to ensure the exit of stale air from the cultivation chamber, it is positioned high up and must have an adequate flow rate for the available space. It is possible to use soundproof boxes to avoid the constant noise of the extractor or alternatively purchase soundproof extractors.


An indispensable tool especially in larger cultivation chambers, in fact it supports the extractor by introducing fresh, clean air into the cultivation chamber, it is positioned low and must have an adequate flow rate for the extractor, according to a rule common to all growers, the extraction chamber cultivation must be in depression, therefore the air coming out must always be greater than the air entering. As with extractors, it is possible to reduce the noise of the appliance by using soundproofed boxes or by using already soundproofed aspirators.

Odor filter:

The best odor filters are those with activated carbon and they allow your cultivation room not to let odors escape outside, they can be positioned both inside the grow room and outside, always connected to the extractor, directly or via duct .

Ventilation duct:

The ventilation duct is necessary as a connection between extractors and air filters, but is also useful for bringing the outgoing air flow to different areas. It is also used in suction to draw air from the outside or distributed along the cultivation chambers for homogeneous distribution of the air. The ventilation ducts can be soundproofed and insulated to attenuate noise and avoid temperature variations.


Fans are necessary for air distribution in the cultivation room, depending on the size different types of fans with adequate power will be needed. In larger cultivation chambers the following are used:

Wall or ceiling fans, used to manage the mass of hot air that accumulates above

Floor fans, used to avoid pockets of stagnant air on the floor

Oscillating pedestal fans mix the air and allow the movement of the plants

Clip-on fans, small fans usually used in grow tents.


Measure the air temperature


Measures the relative humidity of the air


It allows you to adjust an adequate humidity parameter inside the grow room


Prevents humidity in the grow room from going beyond optimal parameters.

How to set up a growbox?

This is a cabinet model that you can use as a reference.

When the growbox is small, the extractor is not necessary because the air enters passively.

How to set up a perfect grow room?

Starting from the assumption that each large cultivation chamber must be designed specifically, below we propose a generic positioning and instrumentation scheme which, if applied, will certainly give excellent results.

What is the inlet and outlet air flow rate in the grow room?

The formula commonly used for calculating the air flow rate and therefore for choosing extractors and aspirators is the following:

Extraction capacity = cultivation chamber volume x air exchange time x system loss

As an example but valid for any grow room:

Having a 120cm x 240cm x 200cm box 5.76 cubic meters

with 2 600w HPS lighting systems

with activated carbon filter.

The minimum calculation would be: 5.76 x 1.25 (loss of effectiveness caused by the filter) per minute

Therefore, considering that the flow rate of extractors and aspirators is measured in cubic metres/hour, the measurement will be:

5.76x60(minutes)x1.25= 432 m3/h

The advice is to use instruments with a flow rate higher than the minimum recommended by at least 30%, so even if in this case a vacuum cleaner with a flow rate of 432 m3/h might be sufficient, it would be better to use a 560 m3/h aspirator.

These indications refer to systems that work with close or direct outlets and duct diameters equal to those of the extractors. In cases where these values ​​are not those considered, it will be advisable to increase the air flow.

All information contained is for informational and educational purposes only. We urge all users not to make any practical use of this information in connection with cannabis seeds. In fact, let us remember that:

In Italy the cultivation of cannabis seeds is prohibited (Art. 28 and 73 of Presidential Decree 309/90) if you do not have a specific authorization (Art. 17 Presidential Decree 309/90)

Therefore, cannabis seeds may be used exclusively for collecting purposes and for genetic preservation and are marketed with the reservation that they are not used by third parties in conflict with the law. Cannabis seeds are excluded from Presidential Decree 309/90, which means that they are not to be considered narcotic substances (L. 412 of 1974, Art. 1, Paragraph 1, Letter B; New York single convention on narcotics of 1961 and table 1 Ministry of Health decree 11 April 2006).

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