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Growing weed indoors with proper ventilation
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In this blog item Good ventilation means a lot of CO2How do you ensure good ventilation in your grow tent?With good ventilation you get strong plantsPrevent odor nuisance with good ventilation and a carbon filter

Growing weed indoors with proper ventilation

In order to get the best yields from your grow tent, you need a good ventilation system. Fresh air must be sucked in and old air must be removed without weed odor. Ventilation in your grow tent ensures a healthy and good climate for the plants, with sufficient CO2 and airflow. The how and why I would like to explain to you.

Good ventilation means a lot of CO2

Many beginning growers think they can increase their yield just by hanging a stronger lamp above their cannabis plants or increasing the amount of nutrition. Partly this is true, with more light the plant gets more energy and can absorb more nutrients from the growing medium such as soil and coco. But to convert these nutrients into usable energy for the plant, the plant needs something else to do this. You can only achieve this with a good climate in the grow tent, such as airflow and ventilation. 

Fresh air, ventilation, and sufficient airflow are essential for indoor growing and will have to be provided continuously. From the fresh air, the plants get carbon dioxide, or CO2. They need this to grow and flower. The plant uses CO2 to convert light into sugars. This is called photosynthesis. As better and stronger grow lights and plant nutrition in the form of boosters come on the market, CO2 generators are being used more and more nowadays. This way of working allows you to generate higher yields. So the factors of air, light and nutrition go hand in hand. If you increase one, you will have to upgrade the other two as well. In a small-scale grow, it is usually sufficient to install a single small extractor. Sucking the air out of the grow room creates a negative pressure. This automatically draws in fresh air through the vents and creates airflow. This eliminates the need for an intake fan.

By sucking in fresh air you prevent stagnant air in the grow tent. Stagnant air in a humid space increases the chance of mold growth and of course we do not want that. The circulating air, or airflow, ensures that the moist air is removed and fresh air is constantly present around the leaves of the plant. 
Inside the leaves are all very small openings, also called stomata. These stomata can open and close and are important for the plant to regulate its processes. Stomata simply consist of two closing cells. When there is a lot of water in the closure cells, they separate and the stomata open. If there is little water in the stomata, they will slacken and close the opening. The plant can then no longer absorb substances but also no substances can leave the plant. The stomata close not only in drought, but also in the dark or if there is too much CO2 present, for example due to insufficient ventilation, they will close. Under ideal conditions, they are open to allow the absorbed water to evaporate and remove excess oxygen from the plant. At the same time, CO2, which is needed for the photosynthesis process, flows in through the stomata. 
You can see that a CO2 generator can have the opposite effect on the development of your plants. In small-scale growing cannabis for personal use, this is therefore not necessary and that is also the reason why they are not available in the Growshop of If you ensure sufficient ventilation, there is never too much but always enough CO2 in the grow space. The same goes for the importance of watering, make sure you don't give too much but prevent dryness.

Ambient Q120+

How do you ensure good ventilation in your grow tent?

Whether your ventilation in your grow tent is up to par can be easily calculated. When growing indoor weed with flowering plants and a strong lamp, it is advisable to refresh the total air content of your grow tent or cannabis coop at least three times a minute.

An example is the HOMEbox Homelab 100 with a growing area of 1 by 1 meter and two Sanlight EVO 3-100 lamps. This grow tent has a capacity of 2 m³ 
(1 x 1 x 2 meters). To refresh the entire contents three times, you need at least an extractor that can extract 3 x 2 m3 = 6 m³ in a minute. The extraction capacity, or flow rate of an extraction fan, is always given in the number of cubic meters per hour. This is converted to 6 m³ x 60 minutes = 346 m³/h. 
For this setup, the Ventilution RVK Tube fan, 365 m³/h, is an ideal exhaust fan.

Another example is a setup with a HOMEbox Homelab 80 with one Sanlight EVO 4-80 lamp. With a capacity of 1.15m³(0.8 x 0.8 x 1.8 meters), you have 3 x 1.15 m³ = 3.45 m³ of air to move in a minute and 207.36 m³/h. The Ventilution Mixed In-Line is therefore very suitable for smaller tents. It can also run at two speeds. For example, it can run at the lowest speed during the growth phase, because the plants will then have enough if the contents are changed twice a minute. And it also saves energy.

In a grow setup with HPS lights like the LUMii Black 600W Kit, it is always advisable to get an exhaust fan with a larger capacity. These HPS lamps produce more heat than an LED lamp. As a result, the temperature in the room may increase and more air and heat must be extracted through the exhaust fan.

With good ventilation you get strong plants

Ventilation and extraction are not only necessary for sufficient CO2 and preventing the development of mold and bad bacteria. Good ventilation also brings an air circulation around the plant that sets the plant in motion, in the same way that wind moves a plant or tree. The movement will make the stem of the plant firmer and thicker, making it stronger and able to support more weight. To add to the wind and make the plants nice and sturdy, place an extra (swing) fan in the grow room in the form of a clip fan or a tower fan. These take up little space or are easy to hang in a grow tent. Because ventilation systems such as these extra fans may suggest that we are supplying equipment used for professional growing, we do not sell these fans. We supply only to hobbyists and patients who grow for their own consumption.

Active Carbon Filter 125mm

Prevent odor nuisance with good ventilation and a carbon filter

Unfortunately, growing cannabis, even on a small scale for personal consumption, is still not legal. But with our tested and certified equipment, it is safer, cleaner and cheaper to grow four cannabis plants yourself. Because only then do you know what you're putting in your joint or vaporizer

It’s important not to bother anyone when you grow! If you are just starting to grow, keep in mind that when the plants are in their flowering phase, they also give off a weed odor. And when I mean weed odor, I really mean weed odor! You yourself will get used to that and as a grower you will find that a nice weed smell, but I can assure you that your neighbors and even their neighbors cannot appreciate the weed odor. Make sure your grow tent does not bother anyone and prevent odor nuisance by using a carbon filter, like the Active Carbon Filter 125mm. When buying this, make sure that you take the matching size that matches the flow rate of the extractor. The complete sets in our webshop are matched and you can easily assemble an installation. You connect the various parts such as extractor and filter with a flexible tube, like the Ventilution Alu Flexible Tubing, 127mm, to each other at the desired size. It does not matter whether the carbon filter is mounted inside or outside the room, as long as the extracted air passes the carbon filter. Keep the outside of the carbon filter clean, this way you will maintain an optimal airflow and the extractor will not be slowed down causing it to use unnecessary power. The carbon in the carbon filter eventually becomes saturated and then no longer absorbs odors. Therefore, replace the carbon filter every year for optimal operation.

If you have any questions about ventilation and extraction, or the equipment, please contact us or drop into one of our physical stores in Roermond or Maastricht for your questions and to get advice. You can read more about the various cultivation methods, ventilation,  and growing weed on our blog page and in our encyclopedia. In the webshop you will find several weed growing books
Sirius does not want to encourage you to grow cannabis, this content is for informational purposes only.

Keep it green,



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