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Easy DIY Carbon Filter for A Grow Room

DIY Carbon Filter for A Grow Room

There are plenty of reasons why one chooses to grow various plants inside a grow room. A major advantage of this is the ability to cultivate under a more controlled condition. The regulation of environmental circumstances such as temperature, amount of light, hydration, among many others allows the growers to develop healthier end produce.

One of the fundamental elements in establishing a grow room is air purification. This is where the use of a carbon filter comes into play. Its main function is to provide decontamination and neutralization of any unwanted odor from the inside of the room.

Today, pre-made filter kits are readily available in the market. Nevertheless, a good quality unit may easily cost you around $100 a pop. So if budget is of concern, making your own carbon filter is also a great and viable alternative. It is simple to make and costs way cheaper than the commercial ones sold.

There are actually two kinds of carbon filters, one intended for water purification and the other for air. In this article, we will particularly focus on the carbon filters made especially for air purification. This sort of 101 guide will provide you with valuable knowledge of what a carbon filter is, the different types, how it works, and as well as a step-by-step procedure in making a DIY carbon filter for your grow room.

What is a carbon filter?

The best way to start the body of this article is to understand what a carbon filter really is. 

Also called a “scrubber”, it is a piece of equipment duly attached to the exhaust system of an isolated room such as a grow tent or room, or a greenhouse. It is specially designed to remove impurities from the air thus helps to promote optimal growth environment and at the same time, odor management.

The carbon filter is chiefly composed of activated carbon material. For ages, carbon or charcoal is widely known for its superior detoxification properties. It is capable of eliminating or filtering out the odor, dust, mold spores, pollens, volatile organic compounds, airborne pathogens and other contaminants that linger around the atmosphere. 

How does carbon filter work?

So how does a carbon filter technically work?

From the word itself, carbon is the superstar on this device. To be precise, it is the activated carbon type that is utilized for this air purification project. What differs this from the regular carbon is that it has been appropriately treated with oxygen.

The said process increases the carbon’s porosity hence results in the expansion of the surface area. Given the larger space, the carbon is now more capable of adsorbing airborne contaminants. This feature is what makes the activated carbon a highly efficient type to use for filtration processes.

Now that we know why activated carbon is the ideal material to use, let us now understand its mechanism of filtration.

The carbon filter simply works by drawing in the unclean air and passing it through the pre-filter first to remove dust and larger particulates. After the pre-filtration, the air is coursed next towards a layer of activated carbon for the elimination of odor, pathogens, moisture, and other contaminants floating in the atmosphere. In the end, the processed air then comes out of the room purified and subdued from any smell.

Having a carbon filter in your own grow room is essentially important. It allows you to eliminate anything that interrupts with the health and safety of the plants you are growing. In that effect, it will help you secure a more conducive environment for your cultivars. 

Furthermore, carbon filtering enables you to eradicate the release of unwanted indoor smell. This is specifically a popular solution for growers cultivating regulated or prohibited plants that comes with a distinct aroma such as marijuana in particular. Neutralizing the emitted odor allows them to stay discreet and ward off unwanted attention from outsiders.

Read Also: King LED Grow Light Review: Is This Grow Light Worthy?

What are the types of carbon filters?

Generally, carbon filters can be classified according to its filtering medium, filter-fan combination, or simply based on the diameter. The various categories will help you easily sort out and come up with the most suitable version according to the needs of your grow room.

Types based on Filtering Medium:

1. Carbon Air Filter

Needless to say, this type is the most common, convenient, and efficient among all the carbon filter types. 

This air filter is basically made of beds of activated carbon. The porosity of the material causes the expansion of the surface area to as much as 2,000 up to 4,000m2per one gram of activated carbon. The smell, moisture, and contaminants are effectively sucked into the formed pores. 

2. Non-Carbon Air Filter

There are also filters that are not necessarily made up of carbon. 

Alternatives like the Particulate Cabin Air Filters are also available in the market. However, this type is limited to removing dust particles only. That being said, they are known to be less efficient and even pricier than its carbon-based counterparts.

Types based on Filter-Fan Combination

This basically refers to the use of a carbon filter with or without the assistance of a fan.

Using a carbon filter solely is ideal to use as a replacement from the old and existing air filter. Should you decide to use this in your set-up, make sure to consider the size, the dimension, and CFM (cubic feet per minute) rating to ensure the adequacy, and also check the flange or the rim itself for proper fitting.

On the other hand, using a carbon filter together with an extraction fan further increases the efficiency of purification. The fan helps by forcing the unclean air in the environment to pass through the activated carbon bed. In this manner, more air can be filtered out leaving the facility less and less contaminated.

Given the advantages of the carbon filter and fan combo, a great majority of the growers favor this option more than using a solo carbon filter. Furthermore, the filter-fan duo also provides more flexibility as certain models of the device may include an option to control the fan speed according to preference.

Types based on the Diameter

Depending on the size of the grow room, the diameter of a suitable carbon filter also varies. The usual size ranges from 4 inches up to 12 inches in diameter and it comes with a CFM rating between 150 up to more than 1,400.  

On a side note, a CFM rating or cubic feet per minute rating basically pertains to the capacity of the fan to induce air movement. This measurement determines the sufficiency of airflow usually within a confined space. In that sense, it is expected that the larger the room, the higher the CFM rating will be required in order to achieve the desired level of ventilation. 

Back to the discussion about diameter, the table below shows the comparison between different sizes of carbon filters.

Size 4-inch 6-inch 8-inch 10-inch 12-inch
CFM Rating 150 – 250 400 600 – 700 1,100 – 1,200 More than 1,400
Grow Room Size (in Feet) 4 x 4

4 x 7

4 x 8

8 x 8

10 x 8

12 x 12 More than 12 x 12 More than 12 x 12

What are the fundamental parts of the carbon filter?

Before proceeding with the how-tos in making your own carbon filter, let us first familiarize ourselves with the three basic parts of the device we are going to work with.

  1. Pre-filter

As the “pre” implies, the pre-filter is the front line of this air purification system. It is a breathable and usually semi-transparent medium with minimal air resistance to easily allow air to pass through. The main task of the pre-filter is to trap bigger size particles such as dust and debris.

2. Activated Carbon Bed

In the activated carbon bed is where all the magic happens. 

The pre-filtered air is further purified in this layer of treated charcoal. The pathogens, chemical fumes, and other contaminants are efficiently drawn into countless pores of the activated carbon. As a result, the impurities and odor from the air are thoroughly eliminated.

3. Air Passage

The air passage is the cylindrical space in the middle of the filter’s two flanges. These said flanges or openings must have precisely exact diameter with the ducting or the inline fan to be able to have a tightly-sealed fitting. 

What are the materials needed to make a carbon filter?

Below is the list of supplies that will be used in making your own carbon filter. And since this is somewhat a DIY project, the items we included here are those that are common and can be readily found in the local stores. Better yet, check if you might already have them in your household.


Common Supplies for DIY Carbon Filter
Pre-Filter Polyester filter media

Knee-high socks

Body (Outer Mesh) Mesh wastebasket

Mesh pencil holder (4.75 inches)

Body (Inner Mesh) PVC drain pipe

Mesh pencil holder (4 inches)

Activated Carbon Bed Activated carbon 
Other supplies Measuring tape


Zip ties

Drill machine

Drill bit (Preferably 5/32)

How to make your own carbon filter?

Now onto the very highlight of this article. 

Here is the step-by-step guide in building a do-it-yourself version of the carbon air filter for your grow room. For reference, the setup below is intended for a 4-inch ducting system. If you plan to make a bigger carbon filter, the nature of supplies and as well as the procedure is still relatively similar, just opt for a bigger diameter of the materials instead.

  1. Ensure the size of the inner and outer mesh complement each other.

The mesh pencil holders basically stand as the skeletal frame of your entire filter. Thus, it is imperative that the size of the two meshes fit accordingly one over the other.  The important factors to consider are as follow:


  • Height – The smaller holder must ideally be around 3/4 of the height of the bigger holder.
  • Diameter – The diameter of the smaller holder must be precisely equivalent to the diameter of the ducting to ensure tight-fitting.
  • Distance – The space between the bigger holder and the smaller holder inside must be at least 12-24mm.

     2.Establish permeability of the inner and outer meshes.

It is given that both of the pencil holders used in this project are already permeable because of its mesh construction. Its bottom parts, however, may not yet be. In that case, you may need to drill holes into them to ensure that air can easily pass through on all sides of the holder. 

Most often, these mesh pencil holders are made of thin metal material. They tend to be not as hard so be extra careful when drilling holes into them. Drill bits as small as 5/32 might work best for this.

3. Insert both of the meshes in separate socks.

You have to use one sock per pencil holder. Stretch out the sock opening and insert the cup, bottom part first. Pull the socks up to fully cover all sides. Do the same with the other pencil holder.

4. Fill the outer mesh with activated carbon.

Carefully pour in activated carbon inside the outer mesh or the larger pencil holder. Fill it only up to half of its length. Make sure to use finely ground activated charcoal especially for smaller carbon filter projects to warrant the efficiency of filtration. 

5. Secure the activated carbon between the meshes.

To ensure that the carbon will not spill over and get wasted, we put the inner mesh or the smaller pencil holder on top of the layer of carbon inside the larger cup. Pull the sock of the larger cup all the way up to include the coverage of the smaller cup.

Now that the activated carbon is all sealed in, carefully turn the setup upside down to evenly distribute the carbon all over the gap between the two meshes. Nonetheless, you also have to leave an equally even layer of carbon between the bottom areas of the cup.

Once the even distribution of carbon is accomplished, carefully turn the setup back to an upright position. Next, you have to ensure that the rim of the inner mesh is aligned with the level of the rim of the outer mesh. Make appropriate adjustments if necessary.

  1. Position the inner mesh socks.

Once both of the meshes are in its proper places, secure now the positioning of the smaller cup’s sock. To do this, carefully stretch out the opening and bring it all the way over to the exterior of the larger cup. Adjust accordingly to keep things completely equal on all sides.

2. Attachment to the ducting or inline fan.

After the carbon filter setup is finished, you may now attach it to the ducting, a 4-inch inline fan in this case. Once you are sure that the filter is snugly fitted into the ducting, that means it cannot be further twisted and is already locked in place, fasten it securely with a zip tip. Double-check the connection again.

How often should you change your DIY carbon filter?

Of course, just like any other air filtration systems, carbon filters are also bound to lose its effectivity over time. Most often, it is expected to last 12 up to 18 months on average. Though, depending on how heavy is the demand for filtration within your grow room, you may need to change it earlier than usual to maintain optimum air purification.

So there you go, those are the basic steps in creating a do-it-yourself carbon filter for your grow room. A simple project that offers tons of benefits especially for the health of the cultivars among many others. It is relatively inexpensive and very easy to make even for the amateur growers out there.

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