A Deep Dive into Growroom Intakes

By Kent Gruetzmacher
Published: September 8, 2021
Presented by AC Infinity Inc.
Key Takeaways

When it comes to setting up an indoor cannabis garden, every grower has certain pieces of equipment they consider essential. Growroom intakes hold a unique place within this spectrum of necessity. Namely because, some growers consider intakes an absolute requirement, while others don’t use them at all.

Our motivations for using intakes are largely shaped by our experiences. While all cannabis plants do best with temperatures below 80°F and humidity levels below 50 percent, every growroom achieves this equilibrium in its own unique way. If you are a tent grower living in a cool climate, you have probably never had to install a dedicated intake. Conversely, if you run a 10,000-watt garden in a warmer region of the world, you probably can’t get by without an intake.


To help you better assess the need for an intake, we put together this definitive guide on the topic. Ideally, this deep dive will give you a more well-rounded understanding of these pieces of cultivation equipment.

Passive and Active Intakes

A passive intake is an opening in the wall of your growroom or tent that is designed specifically to let fresh air pass into the garden. These systems work through your inline fan exhaust system as it pulls fresh air from outside, while expelling stale air. If you wish to use a passive setup, you will need to purchase an inline fan that has a CFM rating far greater than the square footage of your room.


Active intakes utilize fans to pull fresh air from outside the grow room and move it directly into the garden. They key difference here is that active intakes are powered by dedicated pieces of equipment, while passive intakes rely on your exhaust fan to “do the heavy work” in moving fresh air.

Cannabis growing inside a large grow tent.

How Large of Intake Do I Need for My Indoor Garden?

When it comes to intakes and exhausts, negative air pressure is the key to maintaining an ideal environment for plant growth. In turn, the size of your chosen exhaust fan will dictate the intensity of negative air pressure in your garden. This notion applies to both passive and active intakes.


Negative air pressure simply means that more air is exiting than is entering your growroom. When you find a solid balance with negative air pressure, you have strong control over environmental factors like temperature and humidity.

Passive Intake Sizes

Passive intakes work best when air from outside the growroom can pass into the garden relatively unobstructed. Inline fan manufacturer AC Infinity tells us that passive intake openings must be “three to four times larger than the exhaust opening.” As such, if you have an 8-inch exhaust fan, your passive intake opening should be at least 24-inches wide.


Active Intake Sizes

Because active intakes utilize additional fan power, you must be careful not to outsize your exhaust setup. Imbalances between the two fan systems can wreak havoc on negative air pressure. While there is no clean equation that will guide you on sizing an intake fan, you should always choose smaller than the exhaust fan. To illustrate, a 4-inch inline fan is likely a well-matched intake option for a room with a 12-inch exhaust fan.

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Fan Options for Active Intakes

If you decide to go the active intake route, you have a choice between simple booster fans and more powerful inline fans. Again, your choice should be directed by balancing optimal plant growing conditions with negative air pressure constraints.

Booster Fans

Booster fans are relatively inexpensive options for active intake setups. They are especially effective for small grow rooms that need a slight boost with controlling heat and humidity. Booster fans are helpful in getting air moving without unbalancing negative air pressure.

Inline Fans

Inline fans are the most popular choice for active intakes. Companies like AC Infinity have developed environmental controls for inline fans that automatically alter settings according to changes in garden climate. This automation is especially helpful in regions where temperatures fluctuate greatly between day and night, as well as with seasons.

AC Infinity's Air Filter BoxAC Infinity's Air Filter Box

Intake Filter Options

Whether you opt for a passive or active intake, you will need to add a filter to keep harmful pathogens from entering your cannabis garden.

Air Filter Boxes

Products such as the AC Infinity Air Filter Box are designed specifically for intake applications. When used in conjunction with an inline fan, air filter boxes seamlessly trap contaminants down to 0.3 micron-sized dust particles, while also circulating fresh air.

HEPA Filters

Hydroponics product manufacturers have also developed HEPA filters that integrate directly with inline fans and ducting. HEPA stands for “high-efficiency particulate air” and refers only to those filters that can trap particles down to 0.3 microns. HEPA filters are some of the finest filters available and are used to clean air within hospitals and other sensitive environments.

Dust & Bug Filters

Dust and bug filters integrate with inline fans to keep larger particles and bugs from entering your garden. Often referred to as “mushrooms,” these simple pieces of equipment aren’t as effective as HEPA filters, but will do the job in many cases - especially for small gardens.


Every indoor garden achieves an environmental equilibrium according to its own rules. While cannabis plants require specific climactic conditions to thrive, growers find this balance through their own mix of equipment and methodology. If you are unsure if you need an intake for your garden, just keep a careful eye on temperature and humidity levels.

In the end, even small tent gardens can benefit from a dedicated passive intake. Namely because, directing air through a filter and into your garden is a far better way to control pathogens than letting it enter through cracks, zippers, and random openings. Looking at larger indoor gardens, the need for active intakes grows dramatically. Once you begin adding more grow lights and equipment to an operation, it becomes much more difficult to maintain an optimal cultivation environment without an active intake.

AC Infinity logo

AC Infinity is the foremost name in air delivery systems, designing and developing the latest innovations in cooling and ventilation technology. They offer a suite of quiet inline fans that automate the growing progress and track key metrics. Visit or contact [email protected] to learn more.


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Presented By

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Written by Kent Gruetzmacher | Writer, Owner of KCG Content

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Kent Gruetzmacher MFA is a Colorado-based writer and owner of the writing and marketing firm KCG Content. Kent has been working in the cannabis and hydroponics space for over a decade. Beginning in California in 2009, he has held positions in cultivation, operations, marketing, and business development. Looking specifically to writing, Kent has worked with many of the leading publications and marketing agencies in the cannabis space. His writing has been recognized by such icons as Steve D’Angelo and Rick Simpson.

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