How Does a Carbon Filter Work?

Carbon filter uses a highly porous form of carbon, known as activated carbon. Typically derived from coconut shells, bituminous coal or peat, it is heated at high temperatures without oxygen which creates a lattice of tiny pores that greatly increase its surface area.


The massive surface area enables it to trap exponentially more contaminants. As it becomes saturated, however, the adsorption properties are reduced.

It Removes Odors

Carbon is a powerful adsorbent, meaning that it can trap substances in its millions of pores and pockets. When air or liquid contacts carbon, intermolecular forces pull molecules into the carbon, where they are held for good. This physical adsorption is how carbon filters remove odors. Activated carbon is so effective at this task that it is used in the life support systems of spacesuits, to remove unwanted gases from the flow of oxygen to astronauts.

Activated carbon can also filter Volatile Organic Compounds (VOCs), which are gaseous pollutants that aren’t removed by mechanical air filters. The carbon in carbon filters can remove the VOCs created by cigarette smoke, varnish, paint, and cleaning products. It can even eliminate methane, which is a potent greenhouse gas.

There are two types of carbon filters: granular activated carbon (GAC) and carbon block. The difference between the two is that carbon block filters contain a dense, compressed form of carbon. Granular activated carbon, on the other hand, has smaller pieces of carbon that are more porous. This gives the carbon more surface area, which means it can hold more contaminants and toxins. Our vast selection of carbon filters features both forms of carbon, and all are sized to fit standard filter housings. Some include both a standard MERV-rated air filter for particle filtration and a carbon filter for odor/VOC removal, eliminating the need for an additional adsorption filter.

It Removes VOCs

Activated carbon filters remove VOCs (volatile organic compounds) from the air in the form of gases. These chemicals are released from certain solids or liquids and can have many adverse health effects. Carbon filters work to remove VOCs by a process called adsorption. This process causes the carbon to attract and hold onto the contaminant molecules, much in the same way that a magnet attracts iron filings.

The carbon used in a carbon filter is typically granular and can be made from coconut shells, bituminous coal, peat or other raw organic materials high in carbon content. The carbon is heated to very high temperatures without oxygen to bake out any impurities and then treated with even hotter steam to activate it. This process creates lots of cracks and pores in the carbon that give it it’s very high contaminant holding capability.

VOCs are released into the air from things like smoking, cooking, paint, varnishes and cleaners. They can also be emitted by some plants. They tend to have higher concentrations indoors than outdoors, so a carbon filter is an effective tool to reduce the levels of these harmful VOCs.

The quality of the carbon that goes into a carbon filter will determine how well it performs. The pore size of the carbon determines how much it can absorb. The thickness of the carbon bed also has a role to play, as thicker beds have more surface area that can be adrodded. The airflow rate also plays a part in the performance of the filter, as does the amount of contact time between the air and the carbon.

It Removes Chlorine

Chlorine is a highly effective disinfectant that many public water providers use to sterilize municipal tap water. However, chlorine is also known to cause a variety of health problems, including eye and skin irritation, asthma, and even cancer. Fortunately, premium carbon filters are excellent at removing chlorine and the unpleasant taste and odor it leaves behind.

How they do it is by a process called adsorption. Carbon has a huge surface area and lots of tiny pores that contaminant molecules can adhere to. This is why it’s so effective at reducing organic chemicals, VOCs, pesticides, herbicides, chloramines, and other contaminants.

In fact, a single pound of granular activated carbon has enough surface area to cover nearly 125 acres! This is why it’s a top choice for removing chlorine, but premium models also remove other unwanted chemicals.

Carbon block filters, especially those rated one micron or less (meaning they have very small pore sizes), are excellent at reducing a broad range of pollutants, including chloramines and chlorine, as well as VOCs, THMs, mercury, and lead. These types of filters are also able to remove bacteria, cysts like giardia and cryptosporidium, and turbidity from the water. They are also a great way to remove chlorine from city treated water before it goes through a water softener. This prevents the chlorine and chloramines from damaging the resin in your water softener.

It Removes Taste and Odor

Carbon filters remove the objectionable taste and odor caused by chemicals such as hydrogen sulfide (rotten eggs smell) and chlorine. They also filter organic chemicals, such as herbicides and pesticides, from drinking water. This helps to protect our health by limiting the amount of these contaminants that reach our bodies.

These chemicals are not easily dissolved in water so they are trapped by carbon’s adsorption properties. They are attracted to the carbon and adhere like a magnet to its surface. Smaller organic molecules fit the pores of carbon best, whereas larger molecules have less affinity. This is why it’s important to test your water quality for these chemicals.

The carbon that is used in carbon filters is usually ground into a fine powder and then combined with a food-grade binder to form solid blocks called activated carbon. It can be made from coconut shells, bituminous coal, peat, or other raw organic materials. The material is then heated to high temperature in the absence of oxygen to bake it, which opens up its surface area and makes it more porous. This is what gives carbon its really impressive contaminant holding abilities.

It is important to note that carbon filters do not eliminate air particulates such as germs, mold, and dust. It is also important to remember that carbon filters need frequent replacement. They can become saturated with contaminants, which causes them to stop working effectively. A carbon filter may start to smell when it reaches this point, which is a good indication that it needs to be replaced.