Grow Tent Ventilation - How to Ventilate a Grow Space

Grow tent ventilation is a big part of growing indoors and helping your plants by creating a healthy amount of airflow is crucial. Check out our useful graphics, and the full guide on how to ventilate a grow space below!

When growing plants indoors, the grower’s intention is to replicate the environmental elements the plants would be exposed to growing outdoors, but also to control those elements to a very high degree. In order to do so, growers play around with 4 main elements - grow mediums, light, climate, and nutrients. Those four, when combined with proper training, tend to show amazing results in terms of yields and quality.

Manipulating climate can be done in several ways - by lowering or increasing the humidity in the space where plants are growing. Another important way is by manipulating the temperature of the grow space. Certain strains perform better in cooler areas, while others with strong landrace heritage from warm countries will prefer a warmer climate. Then - there’s the major point of air circulation, CO2 and filtering.

Why is grow tent ventilation important?

Grow tent ventilation is a major step in making your plants much happier by introducing a healthy amount of airflow. The reason for creating an airflow has lots to do with biology and the gas properties of oxygen and CO2.

Here’s the crux of the issue: when plants go through photosynthesis they take in CO2 and light, and produce oxygen. Oxygen is lighter than CO2 so it goes up and stays trapped at the top of the tent, while CO2 sinks to the bottom. This can create pockets and have a negative effect on your plants, so that’s where grow tent ventilation steps in to save the day!

The three main elements of grow tent ventilation are:

  1. Carbon filters
  2. Inline fans
  3. Oscillating fans

Carbon Filters

Carbon filters act as emission controllers, as their main purpose is to eliminate unwanted smells and allergens such as pollen coming out of your tent. They are usually attached to the inline duct fan or at the tail end of the ducting on the tent. Check out the graphic below for a simple grow tent ventilation solution.

grow tent ventilation

Inline fans

Inline fans are placed together with the carbon filter and the ducting at the top of the tent. Typically they are either hung with clamps, or tied to tent poles with zip ties They are often called extractors as their main purpose is to pull air from within the tent.
This is vital to creating airflow, which prevents suboptimal humidity and temperature conditions. AC Infinity offers a great selection of inline fans, which you can see alongside other brands which you can see in our web shop.

As you can see on the image above, fresh cool air comes in through the ducting at the bottom of the tent. The fan set between two pieces of ducting draws air from the tent and filters it through the carbon (CO2) filter.
In the meantime, fans attached to the sides of the tent and often hanging from the top of the tent as well, help the air circulate. As we mentioned before - this prevents the different gasses from forming into pockets.
Not only that, but pests such as powdery mildew, mold, and lots of other types of problems won’t start occurring with good grow tent ventilation.

Best inline fan for a 4x4 grow tent

The best inline fan for your needs may not necessarily be the strongest one on the market. Depending on the size of your tent, you can calculate the amount of CFM (Cubic Feet per Minute) that the fan should be able to put out.

If you have a 4x4x8 grow tent, you might want to look into fans which can do around 200-250 CFM. You could also get an inline fan with adjustable speed settings like the AC Infinity S series and T series, which you’ll be able to use with bigger tents when you decide to scale up.

Oscillating fans

Oscillating fans are placed on various points around the grow tent, and depending on the size of the tent you might want to have more than one. They help in creating a healthy amount of airflow and artificially imitate wind.

The best way to do this is to get a couple oscillating fans which can be attached to the metal frame of the grow tent. We strongly recommend checking out our 6-inch oscillating clip-on fan if you’re looking for an easy solution to create an airflow in a small tent. It fits perfectly on all grow tent poles due to it's adaptable mechanism, and it offers a 180° movement in 2 speed settings and 2 joints for tilting in all directions. The fixed clamp feature will also make sure they stay where you put them, without any sliding down.

Growbuds clip-on fan
Seeing how grow tent ventilation is a big part of growing indoors - these items will often come as a part of full grow kit setups. You’ll be glad to hear that we offer one of the best 4x4 grow kit setups which includes both of the above mentioned products - the Growbuds 6-inch fan and an AC Infinity inline fan, and you can check it out below.

Grow room ventilation

Growing in anything bigger than a large tent requires a lot more effort, time and resources put in the setup. However, this will allow you to immensely scale up your operation, and increase the amounts you can grow and harvest in each cycle. Lets leave all other aspects of growing in a room aside, and focus on grow room ventilation.

Grow room ventilation boils down to two main factors - getting air in your room, and getting it out. This can be done by creating negative air pressure, a physical property of air which helps it circulate with a lot less effort. A powerful enough fan will create the pressure within the room, which allows fresh air to enter, but not leave the room. The air leaves the room only through the ventilation shafts and ducting.

However, creating negative air pressure can be quite hard, depending on the size of the room, and costly as well. This is why many grow rooms have a fan to pump air into the room, and a ceiling-tied ventilation setup to pump it out, as you can see on the image below.

grow room ventilation

Keep in mind that you will need somewhat larger ventilation equipment for ventilating a room compared to a tent. This again depends on the size of the room and the volume of the air within the room. You may need to get industrial inline fans and carbon filters, as well as 16 or 20-inch oscillating fans.

Do you need ventilation in a grow tent?

As a first time grower you may not need to get such complex ventilation, in fact you might not even need a tent. First time growers are often recommended to try their hand in growing without any additional help of tents, ventilation and such just to get the feel for it.

Once you have a harvest or two under your belt, you’ll be able to notice the differences in how your plants behave, and how much better your buds get.

However, we would strongly recommend that you get at least a couple oscillating fans to get the imitation of wind going. This could very likely prevent some of the issues such as mildew and mold from forming on your plants.

Remember that humidity levels also play an important role in preventing those two. If the environment is arid enough, they will most likely never even form in the first place.

How do you ventilate a grow tent?

Grow tents are ventilated by introducing a healthy amount of fresh air into the tent. This can be done passively through intakes on the bottom of the tent, or by installing inline fans on the same intakes.

On the ceiling of the tent, the main inline fan combined with the ducting and carbon filter will pull all the air from the tent and send it outwards. This way plants get a bunch of fresh air while removing all the used up air which the plants used throughout the photosynthesis process.

How do you circulate air in a grow tent?

Having air circulate in your tent might not be the best decision for your plants. Plants need CO2 to power their photosynthesis, and they release oxygen in that process.

So, once they go through all the CO2, they’ll only be left with the oxygen they just produced. This is why growers must introduce new air into the grow tent, otherwise their plants will grow at a slower rate and start drooping down.

Can I leave my grow tent open?

Yes, you can leave your grow tent open as a form of ventilation, however this won’t prevent any of the smells and allergens from leaving the tent. If you’re looking to minimize the smells and possibly hide from your landlord or whatever, then leaving your tent open wouldn’t be a very prudent decision.

What is the best grow tent temperature?

Most strains prefer the grow tent temperature to be around 80℉ but some strains may like it a bit cooler or warmer depending on their genetics.

If the genetics of your plants come from windy, mountain areas which have harsh nights and warm days, you might want to keep the temperature around 75℉. You can go even lower than that, but only for a couple hours, as keeping your plants in the cold for too long will ultimately have them freeze and stop growing altogether.

If, on the other hand, they have genetics coming from a warm area, you can push the temperature even up to 85℉, but make sure to put a dehumidifier in the tent as well to keep it mold free.

Keep in mind that adding ventilation to your grow tent may reduce the temperature within the tent, but that change won’t be too significant, maybe 1-3 degrees in total depending on how powerful is your inline fan.