What’s the Difference: HEPA vs. Charcoal (Carbon) Filters


What many people don’t realize is that there are differences between HEPA and charcoal (aka carbon) filters in terms of air purification. There are strengths and weaknesses of each model, so there isn’t necessarily a “best option. The best purifier for you just depends on your personal/household need and preference.


High efficiency particulate air (HEPA) was originally used in World War II in order to remove radioactive particles in the air that proved damaging to soldiers’ respiratory systems. However, in today’s society, HEPA filters have become a common method of filtering household air, such as on vacuums, as it works well on small on small airborne particles.

Household air contains particles that are as small as .5 microns such as bacteria, pet dander, and debris from dust mites. The human body’s natural defense system is made more vulnerable to and because of the inhalation of these contaminants which is why allergists and doctors heavily recommend purifying household air using HEPA filters.

However, while HEPA can remove particles in the air larger than .3 microns, it cannot clean the air of odors, smoke, fumes, or chemicals. While it removes most bacteria and allergens (such as dust, pollen, and mold), it can also trap micro-organisms in its filter. While this may seem like an advantage to HEPA, it’s actually a negative side effect as the orgasms may reproduce/breed thus creating more micro-organisms to be dealt with. This is why HEPA owners need to make sure the HEPA filter also includes a charcoal/carbon filter to filter smokes, gases, fumes, and odors.


Carbon filters come in many forms: impregnated foam material, powder and cloth, and solid carbon. These filters are the most absorbent filters available. These “active” carbons are charcoal that has been treated with oxygen to open pores between carbon atoms. These tiny pores chemically react to contaminants as they pass into and through the filter in order to purify the air or other material(s) around it. When a mineral absorbs something, it does so through a chemical reaction and these filters are no different. Once all of the pores are filled, however, the activated charcoal filters stop working and must be replaced.


Some prime examples of a carbon filter are gas masks and air conditioning units. These filters not only aid in air purification but can also purify liquids, like water, as well such as in coffee machines and aquariums. Even some alcohols, including whiskey, are put through a carbon filter before aging. This process is called “leaching,” and dissolves particles away from solids.

The greatest, and one of only a couple, issue with charcoal/carbon filters is that they don’t remove dust or allergens like HEPA filters do. It seems you cannot have one filter without the other.


Photo by magnoid via Flickr CC License

Photo by Roland O’Daniel via Flickr CC License

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