Activated carbon and its role in air filtration

Humans have been using charcoal to purify water for thousands of years, but it has a multitude of other filtration benefits including a high capacity to filter impurities from the air. What is charcoal (or carbon) and how does it work? Read on to learn more.

Photo of carbon, the remains of burned wood

What is charcoal or carbon?

These terms are interchangeable and refer to the remains of incomplete combustion. When wood is burned, the readily combustible material inside the wood burns away, and if there is insufficient oxygen or heat, black char will be left behind. This is what we all know as charcoal or carbon. Bark, coconut shells, and coal can also be used to make carbon1. Here at Eoleaf, we do not use coal or wood to create our activated charcoal filters: we use coconut shells, an eco-friendly method to create charcoal!

History tells us that carbon was likely first used for filtration purposes by the ancient Egyptians around 1500 BC who used it as a method of removing odours caused by infection in medical settings. Later on, in the 16th through 18th centuries, sailors were known to have stored drinking water in barrels that were charred on the inside to protect it from impurities. Another example of historical use of carbon was during World War I: gas masks were lined with carbon filters to avoid soldiers’ inhalation of deadly gases used by opposing forces. Finding that these filters were only used by some, but not all, of the toxins, the process of activation was applied and utilised in World War II, ultimately leading to the development of modern activated carbon filters for air and water2. Nowadays, activated carbon filters are commonly found in tap water filters, cigarette filters, aquariums, and fallout shelters, to name a few.

What is activated carbon and how does it work?

The goal of activating carbon is to increase its surface area, thus enhancing its filtration properties and its ability to trap gas molecules. This process is done physically or chemically, often by injecting hot air, carbon dioxide, or steam. Since carbon is a carbonaceous material with an already porous structure, activation creates a lattice of tiny pores inside the carbon, and the result is activated carbon that contains hundreds of square metres of internal surface area per gram1! Pore diameter is determined by the ambient temperature and humidity, as well as the material used. Coconut shells create pores of < 2 nanometres, or micro-pores. Wood creates pores larger than 50 nanometres. While pores will always have varying sizes, in air purification, pores measuring 1-2 nanometres are the most ideal1.

Using a process called adsorption (note: not absorption), pollutants stick to the outside of the carbon molecule. Since the carbon has been activated, the increase of surface area creates more space to which the pollutants can stick to, also known as a “bed”. Over time, the bed becomes saturated with organic chemicals (gaseous pollutants), making it impossible to trap more pollutants and rendering it ineffective. It is not always possible to know when your activated carbon filter is saturated; sometimes it will give off a smell, sometimes it will not. This is why it is so important to change activated carbon filters at regular intervals according to the manufacturer’s instructions3.

Diagram of gas molecules sticking to activated carbon using the process of adsorption

What does activated carbon filter out?

Activated carbon can be particularly helpful in filtering out both volatile organic compounds (VOCs) and odours. VOCs are a form of gaseous chemical pollution released into the air usually by anthropogenic means. Everyday products emit VOCs like paints, solvents, new furniture, and DIY activities, as does cigarette smoke. New pieces of furniture can emit VOCs, including formaldehyde (one of the most notable and most dangerous VOCs), for up to two years. Fragrances and sanitising sprays also contain VOCs, as does the famous new car smell, and levels of VOCs can be 2-5 times higher indoors than outdoors.

Bad odours are also effectively removed by activated carbon filters. It is worth noting that air purifiers that only remove pollutants do not combat odours. Some odours that can be reduced with an activated carbon are cooking odours, pet odours, odours caused by mould or mildew, and odours caused by cigarette smoke.

Equip your home and office with an Eoleaf air purifier

All of Eoleaf’s air purification units contain activated carbon filters as part of an 8-technology filtration system. In addition to activated carbon, some of the other technologies included in Eoleaf products are HEPA-certified filters and UV sterilisation. We work hard to ensure that we offer only the most advanced technologies on today’s market, allowing you to benefit from the best filtration devices available. Reach out today to start breathing purer air with an Eoleaf air purifier.

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1 Abdollahi, M., &amp; Hosseini, A. (2014). Charcoal. Encyclopedia of Toxicology, 779–781.

2 Historic journey of activated carbon and breakthroughs . Camfil. (2020, April 7). Retrieved March 3, 2023, from

3 Mazille, F., &amp; Spuhler, D. (2019, May 22). Adsorption (activated carbon). SSWM. Retrieved March 3, 2023, from

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