Best Inline Fans for Grow Rooms & Tents

An inline fan is a critical tool for indoor growers using a grow room, grow tent, or indoor garden. Whereas oscillating fans disperse air around the area, this type of fan also does a great job of moving or extracting air through a growing system.

When you are in the market, you will come across three major types of inline duct fans: axial, centrifugal, and mixed flow.

Each type has strengths and trade-offs. Below are five popular inline fans for grow rooms, followed by buying tips.

This guide is for adults 21+ growing where it is legal.

PRODUCT	DUCT SIZE	AIRFLOW
AC Infinity Cloudline T6 Inline Duct Fan	6-Inch	425 CFM (maker spec)
Hydrofarm ACDF6 Active Air Inline Fan	6-Inch	400 CFM (maker spec)
TerraBloom 6-Inch Inline Duct Fan	6-Inch	Check listing
Vortex S-600 Inline Fan	6-Inch	Check listing
iPower GLFANXINLINE4 Inline Fan	4-Inch	Check listing

Rated CFM is measured with no ducting or filter attached, so real airflow in your setup will be lower.

A Selection of Popular In-Line Fans Among Growers:

AC Infinity Cloudline T6 Quiet Inline Duct Fan

The AC Infinity Cloudline T6 is a mixed flow inline fan with a built-in smart controller.

AC Infinity lists 425 CFM, 30 dBA and a 6-inch duct size, which does a good job of ventilating grow rooms and tents. The model has been updated over the years, so older listings show different numbers.

Its controller reads temperature and humidity and adjusts fan speed to match your settings.

It uses a PWM-controlled EC motor, which runs quietly and efficiently across speed settings.

The maker rates it IP44, meaning it resists dust and splashing water.

Things We Like:

• Mixed flow design is more energy efficient and quieter
• Controller adjusts speed by temperature and humidity (it does not dehumidify on its own)
• Programmable alarms and modes
• PWM-controlled EC motor
• Mixed flow design holds airflow better against ducting and filters

Things We Don’t Like:

• Controller screen may malfunction
• May receive defective inline fan

Hydrofarm ACDF6 Active Air Inline Fan

The ACDF6 Active Air Inline Fan from Hydrofarm is rated at about 400 CFM, per Hydrofarm's product page.

It has a durable ceramic-coated metal housing.

It uses a brushless, thermally protected AC motor with sealed bearings, and Hydrofarm says its components are UL-recognized.

It generates a great volume of airflow, but with a significant amount of noise. However, the noise level won’t be an issue, if your grow room is strategically positioned in the house.

The box comes with mounting hardware along with an eight-feet, 120-volt, pre-wired power cord. You can mount the brackets perpendicular or parallel to the fan.

Things We Like:

• UL-recognized components
• Ceramic-coated metal housing
• Thermally protected AC motor shuts off if it overheats
• Molded impeller
• 120V, pre-wired, eight-foot cord

Things We Don’t Like:

• May receive a unit with bent exhaust fan port
• Maybe a little bit noisy than usual

TerraBloom 6-Inch Inline Duct Fan

Do you want to boost airflow in your indoor grow room or garden? Look no further than the TerraBloom 6-Inch Inline Duct Fan.

It uses an EC motor, which typically draws less power than an AC motor at the same airflow. Check the current listing for rated CFM and wattage.

Speed is fully adjustable, and EC motors usually run without the hum that AC fans make on dimmer-style controllers.

It has a steel housing suited to grow rooms, grow tents and indoor gardens.

The unit comes with a variable speed controller, which is connected to the fan through the provided cable. If disconnected, the fan will function at maximum capacity.

Things We Like:

• Brushless EC motor is highly energy saving
• Fully adjustable controller allows you to effectively increase or decrease airflow
• Steel housing
• Compact design is suitable for grow rooms with minimal space

Things We Don’t Like:

• May end up being noisy after some time

Vortex 347 CFM S Line S-600 Fan, 6″

Have you been searching for a high-performance inline fan that is aesthetically pleasing? Look no further than the Vortex S-600 Inline Fan for grow room.

Its mixed flow impeller makes the fan efficient and quiet.

The speed can be controlled, and it uses permanently lubricated bearings.

The polycarbonate shell cannot rust and helps dampen sound.

It comes with unique mounting brackets on the side of the fan for quick installation. The plastic mounting frame is easily removable.

The rubber gasket that is on the fan actually ensures a tight as well as vibration free duct assembly. This reduces the noise level significantly.

If your fan is not always running, a back-draft damper keeps outside air from flowing back in through the duct. Check the current listing to confirm one is included.

Things We Like:

• Polycarbonate housing is rust resistant and highly durable
• Rubber gasket for a tight, quieter duct connection
• Mixed flow impeller

Things We Don’t Like:

• It’s a bit noisy than usual

iPower 4″ Inline Duct Ventilation Fan HVAC Exhaust Blower for Grow Tent

The iPower GLFANXINLINE4 is a budget 4-inch fan for small tents.

It has a coated metal housing and a permanently lubricated bearing.

You can mount it inside or outside the tent, with the carbon filter inside or outside.

iPower sells the same design in several sizes, so pick the duct size that matches your tent ports.

Things We Like:

• Flexible installation options available
• Moves fresh air powerfully through your target location
• Low-maintenance lubricated bearing
• Flanged ends make duct connection easy

Things We Don’t Like:

• A 4-inch fan is too small for most larger tents

Things You Should Know Before Buying

Types of Inline fans

Inline fans are classified by their impeller design: axial, centrifugal or mixed flow.

• Axial Inline Fan

This is one of the most common forms of inline fan used in grow rooms. A short length of the rigid round duct at least the same diameter as the fan outlet is suitable.

These fans move a lot of air at low pressure. They may not be ideal for long duct length.

An inline axial fan should be installed with the shortest possible duct length to the discharge terminal. You should always refer to the manufacturer’s manual.

• Centrifugal Inline Fan

Unlike axial inline fans, centrifugal inline fans are engineered to create greater pressure, allowing you to use longer lengths of ducting.

This type of fans can be installed in more than one way, including vertical and horizontal installation.

They are the usual choice when you add a carbon filter, which adds a lot of resistance.

• Mixed Flow Inline Fans

Mixed flow inline fans can fill the gap between the axial and centrifugal inline fans, balancing the best of both worlds. They’re basically hybrids with mixed characteristics.

Mixed flow units have unique designs that consume less power to achieve the same performance.

The inclined shroud cover of mixed flow inline fans can direct as well as guide airflow direction into the wheel efficiently. This helps to increase pressure while reducing power consumption.

They strike a balance between power use, air pressure and noise.

Duct Size

Usually, velocity and cubic feet per minute are used to determine the duct size. All inline fans are rated for a particular duct size, such as 4-inch or 6-inch.

Match the duct to the fan's inlet and outlet size. Undersized ducting chokes airflow, and every bend and extra foot of duct cuts it further.

Cubic Feet and Airflow

There are different sized fans for different growing areas, depending on your total cubic feet.

To calculate the cubic feet of your grow room multiply the length by the width, and the height of your grow area.

For example, a tent that measures four by two by five feet holds 40 cubic feet. A common rule of thumb is a fan that can exchange the full volume about once a minute, so at least 40 CFM.

Carbon filters, ducting and hot lights all raise the need, so growers usually size up well beyond that minimum. A 4-inch fan is plenty for this tent, and a speed controller lets you dial it back.

Choosing the right size inline fan is important if you want to optimize your grow space.

Durable Construction

You want to invest in a unit that will serve your grow room long-term. As such, you should choose a fan with durable construction.

Choose a well-balanced unit that minimizes vibration, with sealed or permanently lubricated bearings.

For superior duct connection, we advise you to choose a unit that has a rubber gasket, which not only helps with eliminating vibration but also dampens sound.

Don’t just choose a durable construction. Also, make sure it is easy to install. The unit you select must come complete with mounting hardware.

Unlocking the mounting bracket should not be hard. Installing the ducting system on the mounting bracket should be simple.

Most growers exhaust slightly more air than comes in, which creates gentle negative pressure. The tent walls pull in a little, and odors stay inside to pass through the carbon filter.

If the walls suck in hard, open more passive intake vents. Starving a fan of intake air cuts airflow and makes it work harder.

Final Words

Like proper grow lights, hydroponics, and soil, good ventilation is crucial for a successful grow operation. An inline fan is the main tool for removing heat and humidity from a grow room, and moving air helps limit mold such as Botrytis, according to a review of cannabis diseases.

The five fans above are popular, proven choices.

However, if you choose to extend your search beyond what we have covered in this guide, remember to use our buying tips.

Of the three types of inline duct fans, we strongly recommend mixed flow designs because they offer the best of both worlds in terms of power consumption and air pressure. Also, go for a versatile inline fan that comes with flexible mounting options.

Sources

• Cloudline T6 Quiet Inline Fan, AC Infinity
• Active Air 6" Inline Duct Fan, 400 CFM, Hydrofarm
• Emerging diseases of Cannabis sativa and sustainable management, Pest Management Science (via NIH PMC)