Why is Carbon Used in Air Purifiers?

Activated carbon is used in home air purifiers because, like air sponges, carbon filters trap airborne odors and gases. The reason it is called "activated" charcoal is that it’s been treated with oxygen. This opens up tiny pores between the carbon atoms and the pores trap the odors and gases. Carbon granules have a very convoluted surface, providing it with a large surface area to volume ratio, which makes carbon filters tops for trapping the gases that go through particulate filters first. But eventually, the pores become clogged with contaminants, and the filters must be replaced to function properly.


(Picture Caption) You an see in these closeups that activated carbon has a honeycomb formation. The odors and gases become trapped in the honeycomb pores.

Is One Activated Carbon Filter as Good as the Next?

No. Sometimes activated carbon is impregnated with special materials that make them more effective at trapping odors and gases. These specially enhanced activated carbon filters are able to remove the so-called volatile organic compounds, or VOCs from the air.

How Much Activated Carbon is Necessary?

In general, more carbon is better because as soon as all the pores in the surface of an activated carbon filter are plugged, the filter is no longer effective. Greater amounts of carbon will make a filter work better and last longer than a filter that only has a small amount of carbon. Filters with only small amounts of carbon can become useless in a matter of weeks. The best activated carbon filters have larger amounts of activated carbon. Some of them can last for over 18 months.

How Thick Should the Carbon Filter Be?

The thicker the better. The more time that the pollutant has contact with activated carbon, the better its chances of being trapped. Therefore, the thicker the layer of activated carbon the air flows through, the better the results.

What is the Difference Between Pads Impregnated with Carbon and Granular Activated Carbon?

Granular activated carbon is better. In fact, granulated activated carbon is better than a carbon pad filter of two inches thick or more. That’s because it has a greater surface area to volume ratio for trapping gases and odors than the impregnated pad filter. Pad filters with activated carbon will have to be changed far more frequently than activated carbon granule filters. The more contact the air has with the carbon, the greater the chances of the pollutants being trapped.

In summary, activated carbon is considered a "miracle filter" by many researchers. It has a great capacity for getting rid of unpleasant odors and volatile organic compounds, including those from pesticides. Activated carbon acts as an air sponge, trapping pollutants in its tiny pores. Activated carbon is the most preferred substance for removing numerous possibly hazardous or carcinogenic chemicals in the air. It’s likely that you will need to replace carbon filters every year or more depending on your air quality.

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