Do I need an Intake Fan for my Grow Tent?

When it comes to growing cannabis indoors, air intake fans are usually what many growers tend to leave out of the equation, as you can usually do just fine with passive ventilation and many growers are left wondering, do I really need an intake fan for my grow tent? However, you still need to know why they’re useful and the benefits you can obtain from installing one.

What is an air intake fan for a grow tent?

An indoor air intake fan is a device used to bring fresh air into your grow room from outside or from a different room in your house. It’s done to cool down the air in the room and replenish the amount of oxygen and carbon dioxide in the air.

Differences between air intake and extractor fans

An indoor intake fan is essentially the same thing as an extractor fan – they can be reversed as needed and used interchangeable. However, in order to do this correctly you need to keep the strength of the air flow in mind. When installing a ventilation system in your grow room, keep in mind that the air intake fan should only have one quarter of the strength of your extractor fan. This is done to keep a balanced pressure in the room so that the CO2 and O2 levels don’t get out of whack.

Types of Air Intake | Active & Passive

You can increase the air intake to your grow room or tent in various different ways; you can do it actively by using an intake fan or passively if you have a strong extractor fan and passive filtration grids.

When growing in tents indoors you’ll always want to have slight passive ventilation, which can help any extra aromas to stay in the tent rather than leak outside. Passive ventilation also improves any carbon filters you might have set up to your extractor fan.

Passive Indoor Air Intake

When intaking air passively rather than actively you’ll be saving money and time when it comes to buying an intake fan and setting it up. Without one, your grow room should be much quieter too, as it won’t be adding its vibrations to the mix. However, when using passive air intake you don’t know the exact airflow and it’s easier for insects or fungi to get in. We recommend placing some netting over your intake grids if you have them, and you’ll also need to make sure that no light is getting through.

intake fan for grow tent

Passive intraction is usually something that doesn’t need to be set up, especially when working with stronger extractor fans – even if you don’t think your grow tent is capable of passive intraction, if your extractor is strong enough you should notice the walls of your grow tent bending inwards slightly, as the air is sucked back in through any holes in the corners etc.

Active Indoor Air Intake

When setting up an active indoor air intake using an intake fan or a reversed extractor fan, you’ll need to set it up near the bottom of the grow tent or grow room in order to intake the freshest air possible.

intake fan for grow tent

The perfect way to set up an air intake system is to use a section of aluminum tubing that allows you to direct the flow of fresh air in around your plants. You should also attach an anti-pollen filter that can keep insects and pathogens out of your grow room. If necessary you can also install a chimney hat on the outside if you’re worried about animals getting in.

Also, we highly recommend placing a spinning fan near your air intake, whether it’s passive or active, and have it facing your plants. This is done to make sure that the fresh air doesn’t end up stagnating in the corner and actually reaches your plants.

How long should you have your air intake fan on?

A general rule of thumb is to have intake fans on for 15 minutes and off for 45 minutes in an hourly pattern. However, if you have a bit more experience you can adjust the air flow and the amount of time it’s on depending on the needs in your grow room. You’ll need to keep in mind various parameters such as humidity, temperature, CO2, O2 and the phase that your plants are in. You can do this manually by playing around with the timer of your intake fan, the strength of your extraction fan and by using a thermos-hygrometer. However, you can simplify this process by using a thermostat and a climate controller.

How strong should your intake fan be?

In order to figure out the square meterage of air flow needed from your intake fan, you’ll need to figure out how strong your extractor fan is, which you should be able to find in the instructions or on the box. You’ll need to divide the strength by four and the resulting number is the required strength of your intake fan.

If you don’t have your extractor fan yet and you can’t do the math, you can also use another method; you’ll need to multiply the width, length and height of your grow tent or grow room and then multiply the result by 60 (minutes per hour) and then divide the resulting amount by 4.

Grow room example:

  • 2 x 2.5 x 2.1m (width, length and height)
  • Multiply all of these numbers and you get 10.5
  • Now, multiply this by 60 and you get 630

630 is the m3/h strength your extractor fan will need, and when divided by 4 you get your air intake results.

  • The end result would be 630 / 4 = 157.5

157.5m3/h is how strong your intake fan will need to be to keep up with your extractor Intake Fans

sunon intake fan

Sunon Intake Fan for Grow Tent

These types of smaller intake fans are the most used kind by cannabis growers that tend to make their own homemade tents and need small, weaker devices; it’s affordable and does what it’s supposed to. However, you’ll need to add some meshing to it as plenty of light can get in through the gaps in the blades.


inline intake fanInline Intake Fan for Grow Tent

This is another intake fan that cannabis growers tend to use in grow tents or in smaller grow rooms. These round extractor fans can easily be turned and used as an intake fan or as a little extra boost halfway through the piping for your normal extractor fan. This particular model does not compress air, it simply absorbs it and pushes it out gently.


2 speed intake fanTwo Speed Intake Fan for Grow Tent

The two speed intake fan is also perfect for indoor growing. It looks quite different from the inline intractor fan; this is because it comes with two reducers for setting it up and it also allows you to choose between two different speeds; versatile and functional.

These are just a few of the usual intake fans used in grow rooms with just a few lights and in classic 1.2×1.2m grow tents. However, like we mentioned before, you can use pretty much any extractor fan as an intake fan too; just make sure to use devices that are strong enough for your grow room. If you’re working in a large grow room with 10 lights or more, for example, you’ll need to get a powerful enough extractor fan and its corresponding intake fan.