What is activated carbon filtration?

Activated carbon is one of the most widely used technologies in the air and water purification industries. What is activated carbon? Why does it undergo activation? How can an activated carbon filter improve your indoor air quality? Read on to learn more.

A photo of carbon

Carbon: natural air filtration and water treatment

What is carbon or charcoal?

The terms ‘carbon’ and ‘charcoal’ are used to describe the substance that remains after incomplete combustion occurs. The first examples of using carbon for filtration purposes can be traced all the way back to ancient Egypt.

Nowadays, we use carbon filters in many applications including aquariums, cigarette filters, and, of course, filters for air and water treatment.

What is activated carbon?

Activated carbon is a carbonaceous material that has been specially treated to enhance its ability to attract and remove other compounds from air and water. The goal of carbon activation is to increase its surface area (also referred to as a ‘bed’) to allow it to combat a greater number of air pollutants. This results in the removal of these pollutants from your breathing air. Its bed structure is porous, making it capable of fixing itself to pollution particles and gases. In an area of 400 to 2,500 m2, one gram of carbon that has undergone activation can single-handedly absorb the pollutants present

Activated carbon (also known as ‘activated charcoal’) is just one technology (out of 8!) employed by Eoleaf’s air purification devices. It is commonly used in the removal of contaminants from both air filters and water filters. In fact, it is one of the most common filtration compounds in the industrial world. Carbon that has undergone activation is an incredibly versatile substance and can filter both gaseous and aqueous pollutants. It can often be found in water treatment technologies like drinking water filters, cigarette filters, aquariums, and fallout shelters. 

How does activated carbon work?

Activated carbon works by using a process called adsorption. This is when pollution particles stick to the outside of the carbon molecule. Carbon’s increased surface area (‘bed’) as a result of the activation process provides more space to which pollutants can adhere. Thanks to activation, this newly enhanced surface area allows the activated carbon to trap more pollutants in its bed. The adsorption process only concerns the surface of the solid.

The process of adsorption

This process should not be confused with the process of absorption. This is when gas or liquid molecules become incorporated into the whole volume of a solid.

Which types of pollution are targeted by activated carbon?

In Eoleaf products, following the pre-filter (which is used to capture large particles like hair and dust), the activated carbon filter is next in line in the air purification process.

The activated carbon filters used in our products have a high density and high adsorption capacity. This enables them to clean the air of many chemical pollutant molecules and volatile organic compounds (VOCs).

Volatile organic compounds (VOCs) and chemical pollutants

VOCs are harmful volatile gases and are result of polluting activities in both the domestic and industrial sectors. Some of their most common sources are sprays (including air fresheners and fragrances), organic solvents, cleaning products, synthetic agents, and more, and they are directly responsible for degrading air quality.

Certain VOCs are carcinogenic to human health, especially formaldehyde and benzene. These VOCs are often found in many industrial processes. However, you find them often in new furniture. Furniture releases these harmful, volatile gases and molecules into your space for up to two years! Formaldehyde and benzene are also found in building materials, cigarette smoke, beauty products, disinfectants, pesticides, and adhesives.

The VOCs that are most easily absorbed by the activated carbon filter are nitrogen oxides, CO2 and CO, formaldehyde, acetone, benzene, ethanol, butane, and toluene.

Activated carbon's mode of action

Unpleasant odours

Activated carbon filters also work effectively in removing bad odours. Unpleasant odours are common in indoor spaces and may be generated from cooking, mould, waste, bathrooms, plumbing, and more. This is why some storage boxes for cheese and vacuum cleaners use activated carbon.

Smoke and second-hand smoking

Another great application for activated carbon filters is its action in the removal of all types of smoke from the air. Activated carbon filtration is an excellent way to protect your health and the health of your loved ones from the chemical fumes and dangerous molecules produced by first-hand, second-hand, and third-hand cigarette smoke.

A burning cigarette releasing smoke

Activated carbon’s effectiveness in air purification

The effectiveness of an activated carbon filter depends upon many factors: some, for example, are the material with which it is made, its shape and density, and its contact surface, among others.

Materials used to make activated carbon

Various materials are used as a base of the process of making activated carbon including wood, bark, coal, corncobs, coffee shells, wheat straw, and coconut shells. Here at Eoleaf, we use coconut shells, an eco-friendly method to create charcoal! Since coconut shells are typically a wasted material following coconut processing, repurposing them for activated carbon is a great way to turn waste into a high-value product. Using coconut shells for activated carbon also produces less dust and fine particles compared to wood or coal.

When activated, coconut shells achieve an increased porosity with pores of < 2 nanometres in size (micropores). Pores measuring 1 to 2 nanometres are ideal, compared to wood which produces pores of 50 nanometres.

Shape and exchanging surface between activated carbon and airflow

Our activated carbon filter is cylindrical in shape. This increases its contact surface and volume as it comes into contact with airflow.


Since the purpose of carbon activation is to act on both gaseous and liquid pollutants, it is worth noting that the relative humidity level (concentration of water molecules) of the ambient air also impacts its performance. For example, in a room that is too humid, the activated carbon will act like a sponge and absorb the water present in the air. This is one of the reasons why we recommend our customers to reduce humidity in their indoor spaces, only using our devices in an environment that does not exceed a humidity level of 65%. If the humidity level exceeds 65%, it is recommended that you supplement your air purifier with a dehumidifier to reduce humidity levels to keep the activated carbon filter from absorbing too many water molecules.

The number of filtration technologies

Eoleaf’s devices come equipped with 8 different filtration technologies with each technology targeting a specific type of air pollution. These technologies not only remove the three main types of air pollutants found in indoor spaces (chemical pollution like VOCs, biological pollution like germs and allergens, and fine particle pollution or PM) and protect your health, but they protect the longevity of your activated carbon filter, too.  The presence of other filters allows the activated carbon filter to focus on the particles it removes best: chemical pollution like VOCs and unpleasant odours. In our devices, you will find the following air filtration and depollution technologies:

Eoleaf's 8-step air purification method

Grain size and density

There are two main types of activated carbon filters used to reduce airborne pollutant concentrations and improve air quality:

  1. Granular activated carbon (GAC) – GAC filters contain granular particles up to 3 mm in diameter; GAC filters are lighter, more efficient, and more durable than other types of granular activated carbon filters
  2. Fibre activated carbon (FAC) – contain much smaller grain sizes (10 to 50 microns) and have faster adsorption than GAC filters; they are usually cheaper and are, thus, a preferred technology by manufacturers

Eoleaf uses a combination of granular activated carbon (GAC) and fibre activated carbon (FAC) technologies in our activated carbon filters. This gives our customers the best of both worlds.

The Eoleaf difference

The benefits of carbon that has undergone activation speak for themselves and explain why activated carbon is such a popular filtration material. It is a very versatile material with a comprehensive method of action and long service life. This is why we have chosen to include this technology in all of our air purifier devices. To read more about activated carbon, refer to our article here.

Our air purification experts are here to answer any and all of your questions regarding activated carbon and air purification in general: reach out any time. Also, feel free to refer to our in-depth Buying Guide to read more about our products and learn which device is right for your needs. Start protecting your health and improve your air quality today with Eoleaf.

Eoleaf's AEROPRO 100 air purifier

Frequently asked questions

Can activated carbon filters remove VOCs (volatile organic compounds) from indoor air?

Yes! VOCs are one of the main pollutant types targeted by activated carbon filters. Before purchasing an air purifier with an activated carbon filter, ask your manufacturer how much activated carbon is contained within the activated carbon filter. The heavier the filter is, the better! This is due to the fact that with devices containing more activated carbon, there is more carbon surface area, making it possible to absorb more chemical pollution like VOCs. For example, the activated carbon filter in Eoleaf’s AEROPRO 150 contains an impressive 1.2 kg of activated carbon!

How often should activated carbon filters be replaced for optimal performance?

This is an answer that will vary depending upon your model of air purifier. Lower-quality activated carbon filters will need to be changed more often, sometimes every three or six months. Also, certain devices have multiple filters that may have different changing intervals and must be changed separately (for example, separated HEPA filters and activated carbon filters). Many Dyson air purifiers have this, for example, requiring a great deal of organisation for the end user. High-quality filters, like those found in Eoleaf’s devices, only need replacing once a year. In fact, Eoleaf’s filter blocks contain 8 different filtration technologies, including an activated carbon filter, but since all layers are found within one filter block, filter changes are made easy and can be done once annually.

Can activated carbon filters capture particulate matter like dust and pollen?

No. Activated carbon filters do not target particulate matter (like PM10, PM2.5, and PM0.1). Activated carbon filters specialise in the removal of chemical pollution (like VOCs) and unpleasant odours. In order to combat fine particles like PM, it is important to purchase a device that also contains a HEPA-certified filter. These filters are third-party tested and guaranteed to remove 99.97% of all air pollutants down to 0.01 microns in a single pass.

Are there any health benefits to using activated carbon air filtration in homes?

Absolutely! Activated carbon has been used for centuries for its filtration capabilities. The first traces of using carbon for filtration go back to the ancient Egyptians! Activated carbon is an extremely efficient method to remove chemical pollution (like VOCs) and bad odours from the air. Chemical pollution has been linked to many different negative health effects, and bad odours may have a harmful impact on your overall well-being.

How can I tell when an activated carbon filter needs to be replaced?

It is not always possible to know when an activated carbon filter needs to be replaced just by using your senses alone. This is why Eoleaf recommends following a strict schedule of replacing your air purifier’s filter once every year. This is the best way to ensure that you are not using a device with an oversaturated filter.

Can activated carbon air filters help reduce allergy and asthma symptoms?

Allergy and asthma symptoms are not usually caused by chemical pollution or odours, the two types of air pollution targeted by activated carbon. Allergies and asthma symptoms are often triggered by the presence of allergens and fine particle pollution. In order to rid your indoor air of these pollutants, it is important to purchase a device that contains a HEPA-certified filter in addition to an activated carbon filter. Both filters working together will ensure the removal of all types of air pollution. Or, even better – purchase a device like Eoleaf’s that contains 8 different air filtration technologies!

Are activated carbon filters effective in smoke removal from indoor air?

Activated carbon filters help combat the chemical pollution that is found in cigarette smoke, for example. Cigarette smoke contains over 250 harmful chemicals, many of them carcinogenic, which are released into the air in the form of second-hand smoke. Second-hand smoke is a complex mixture of fine particles, VOCs, and heavy metals. Activated carbon filters will combat VOCs, but in order to fight fine particles and heavy metals, a HEPA-certified filter is also required.

How do temperature and humidity affect the performance of activated carbon filters?

Most air purifier filters should not be exposed to drastic temperature or humidity changes. This may cause damage to the filter’s delicate fibres. This is why Eoleaf never recommends installing an air purifier in rooms that are particularly humid like bathrooms or laundry rooms.

What size of activated carbon filter do I need for my room or house?

Before purchasing an air purifier, it is important to ensure that it is properly sized to your space. If you have a small space, you will require a smaller air purifier. The same goes for a larger space: you will require a larger air purifier. Eoleaf offers three different models, meaning that our devices are capable of accommodating rooms of any size:

Eoleaf's range of air purifiers

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