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Many people are surprised when they begin considering a room air purifier, at the important role activated carbon plays in removing odors, chemicals, and gases. Often, the only people familiar with activated carbon are those who have had aquariums. Surprisingly, activated carbon can be used in an air purifier and in a water purifier. It has what is referred to as high 'adsorption capacity'. That's adsorption with a 'd' as opposed to 'absorption.' In adsorption, molecules 'adhere' to a solid surface, instead of being absorbed into them.
In an air purifier and a water purifier, activated carbon has a tremendous capacity for adsorption and also has a tremendous surface area, so there are more places for the molecules of chemicals to bond to the carbon. Some air purifier models have thin carbon mats and other models have pounds of granulated activated carbon. Why the difference? Those with small amounts of activated carbon, a few ounces for example, in the form of a flat mat, are not intended to remove a lot of chemicals over a long period of time. In that case, the bonding sites fill up quickly. The air purifier models with pounds of activated carbon are intended to remove chemicals and odors for a period of years. The length of time depends on the type and amount of activated carbon in the air purifier and the composition of the air. Generally, the more activated carbon in the air purifier, the better.

Another factor in the ability of an air purifier to clean a room is the blend of activated carbon used in it. Manufacturers develop different blends of activated carbon and other media which remove different chemicals. For example, some blend activated carbon with zeolite or potassium, others blend it with impregnated active alumina. There are also many different types and blends of activated carbon itself. Some air purifier models are intended through a particular blend to remove formaldehyde, others to remove something like volatile organic compounds. The list of blends and capabilities that can be found in the different air purifier models on the market is long. An understanding of the environment in which a particular air purifier will be used, will help the user in choosing the one that will be most effective. The more details about what chemicals from cleaners, perfumes, solvents, etc., that a person can determine, the better.

Of course, many air purifier models are designed primarily to remove particulates like dust and pollens, and may not be intended for long term removal of chemicals. Most HEPA (high energy particulate arresting) air purifier products as well as electrostatic or ionization technology units will include an activated carbon mat or small amount of carbon. However, the type and amount of the carbon varies dramatically. Users who are concerned about chemical removal should make sure the air purifier they choose is designed to remove chemicals and has a significant amount of activated carbon blended for their particular need. Most of the higher end HEPA air purifier models designed by reputable manufacturers do include activated carbon in amounts intended for high adsorption of chemicals.