How to Set up Ventilation in Grow Tent

Ventilation is an essential component of your indoor grow tent, and it helps in many ways. This will be a complete guide on how to set up ventilation in grow tent. Stagnant air can cause a lot of problems inside a grow tent. Mold, mildew and bugs can occur if the air is stagnant or too humid. Using a ventilation system ensures proper airflow within the tent and constantly provides fresh air for the plants to breathe. Another very important reason is smell. During the flowering stage marijuana plants can have a very strong odour. Using a ventilation system with a carbon filter will reduce almost all the smell in the exhaust air leaving your tent. 

What you need to get started

Before you can start building your ventilation system you will need to make sure you have everything you need to get started. These items can be bought independently or you can buy it as a complete kit. Heres the 4 main components of any ventilation system.

  1. Inline fan 
  2. Carbon filter 
  3. Ducting
  4. Clamps

Inline fans for grow tents

The inline fan is what creates the suction and pulls the air out of your tent. When the fan is powered on it will create a negative air pressure inside your grow tent. This will ensure all the stale air will be vented out through the exhaust and a constant supply of fresh will be pumped in. You must make sure you correctly size your fan to fit your grow tent.

Carbon filters for grow tents

In the final stages of flowering your buds will be very potent and have a strong odour (which is a good thing). However if you are trying to keep your grow tent stealth, or just don’t want your entire house to smell then a carbon filter is a must! Carbon filters are the first step in your ventilation system. All the air in your grow tent will pass through the carbon filter which then removes all the odour. 

Ducting for grow tents

In order to connect all your components together you will need to use ductwork and duct clamps. The ducting will provide a path for the air to travel throughout the system and eventually exhaust outside your tent. 

Duct Clamps

Duct clamps are simply used to secure your ductwork to your components and help create an air tight connection. Make sure they your ductwork is attached flush and then put on the clamp and tighten.

How to Set up Ventilation in a Grow Tent

How to Set up Ventilation in a Grow Tent

  1. Install Fan

    First you will need to pick a good location for your fan. I like to keep mine outside of the tent to save space.

  2. Install carbon filter

    The next step is to install the carbon filter. Most carbon filters will come with a set of straps. You can attached these to the frame of the tent and hang the carbon filter. Make sure you are far enough away from your lights and plants.

  3. Install Ductwork

    The Ducting is what connects all your components together. Once you have installed the fan, carbon filter, and light you are ready to attach them together using ducting. See the picture below to see which order to connect everything.

Ventilation Flow Chart
Correct order of installing ventilation in a grow tent

How Many CFM Do I Need for a Grow Tent?

Now that you know how to set up the ventilation system, you might be asking “What size fan do I need for a grow tent?” Well that is a very important question, and it really depends on what size of tent you have. Obviously the larger the tent, the more air it will contain therefore requiring a large fan. You must also considering which grow lights you are using. MH/HPS will produce much more heat compared to LED. This means you will want a more powerful fan to help remove heat and control the temperature. Every component you add, and every bend you make in the ducting will require more CFM to draw the air through the system.

How much CFM for a 4×4 Grow tent?

One of the most popular choices of grow tents is the 4×4. In order to find the required CFM there is a fairly simple equation you can do.

First we will calculate the base CFM for the tent.

Length x Width x Height - 4ft x 4ft x 7ft = 112 Cubic Feet

This means 112 CFM is the base amount required. 

Next we need to add on any other components using these multipliers:
- 25% for ducting with a single bend
- 60% for a standard carbon filter
- 50% for lighting ( can vary depending on grow light type and wattage)


Base CFM x 25% x 60% x 50%

112 x 1.25 x 1.6 x 1.5
= 336 CFM

Now we know the minimum CFM required for a 4x4 grow tent is 336 CFM. 

One thing to keep in mind is that inline fans will generally come in standard sizes. The best practice is to calculate your required CFM, and then round up to the next highest size. For my 4×4 grow tent I went with a 6 Inch 440 CFM inline fan.

For any other sized grow tent see the chart below!

How Many CFM for 3×3, 5×5 or Other Size Grow Tent?

2′ x 2′ x 7′60 CFM
3′ x 3′ x 7′110 CFM
4′ x 4′ x 7′215 CFM
5′ x 5′ x 7′340 CFM
4′ x 6′ x 7′320 CFM
8′ x 8′ x 7′850 CFM
10′ x 10′ x 7′1350 CFM
12′ x 12′ x 7′1950 CFM
Note: These are general guidelines. Round up to the nearest size fan you can find. For larger tents you may need to use multiple inline fans for intake and exhaust.

Oscillating Fans for Grow Tents

In addition to your ventilation system, its always a good idea to have at least 1 or 2 oscillating fans in your grow tent. The inline fan will do a great job of exhausting the old stale air, and bring in fresh air, but its the oscillating fans that help create the air flow within the tent. The fans also imitate the wind and help strengthen the stalk and branches of your marijuana plants. Don’t go to big, generally the best practice is to have two small fans. One on the top corner, and one in the opposite bottom corner. To make things easy you can purchase fans that will clamp right on to the frame of your tent allowing you to place it almost anywhere and making it very easy to move if needed.


Now that you have made it to the end of this guide you should be prepared to set up your own ventilation system. If you have any questions about the process head over to the contact page and feel free to email me! I will always do my best to respond to every question.

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