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Activated Carbon Air Filters

Activated carbon is a porous charcoal used in air-filters.
Ashwini Kulkarni Sule Nov 22, 2018
Charcoal has been used as water and air purifier since ages. It has properties that help remove chemical impurities. Activated carbon has large surface area; 5 grams of this carbon type has a surface area equivalent to the size of a football field. Activation of carbon gives it a slightly electropositive charge, to attract the negatively charged impurities.

Manufacturing

Activated carbon is manufactured from nutshells, coconut husks, hardwood, and other substances that have a high carbon content. These substances are burned at a very high temperature, in the presence of steam, and in the absence of oxygen.
This process aims at removing all non-carbon contents from the source material. The residue resulting from the process has very high porosity, and hence, a very large surface area.

Working

The positively charged carbon attracts negatively charged impurities. This process is called adsorption. The gas molecules of chemicals and other impurities, get stuck in the numerous tiny pores on the carbon pad's surface, which is present in the filter.
The amount of impurities attracted by the filter would be in proportion with the amount of carbon and its thickness. The large surface area allows more pollutants to come in contact of the filter, and hence, cleans large volumes of air. A small piece of carbon in the air filter is capable of removing impurities from an entire house.
These filters are better than other odor removing mechanisms, like sprays and fresheners. While they only fool our senses into believing that there is no odor, the smell still exists. Carbon filters practically eliminate the odor by capturing the impurities or gas molecules responsible for it.
Activated carbon is not used as the sole filtering mechanism. Most air filters use it as a secondary filter in their systems. The different types of filters that use this type of carbon are:
  • Activated Carbon Pleated Panel Filters: They eliminate particulate pollutants, gases, and odors.
  • Chemically Enhanced Carbon Pleated Panel Filters: Apart from gases and odors, they also remove the volatile organic compounds (VOCs).
  • High Efficiency Gas Adsorption (HEGA) Filters: They are capable of effectively removing a wide range of vapors and odors.
  • Carbon Loaded Rigid Box Filters: They are capable of removing odors effectively even with a small concentration of active carbon.
  • High Mass Zero Dust (HMZD) Panels: They are suitable for the areas, which demand high quality of clean air like airports, museums, water-treatment plants, semi-conductor manufacturing units, etc.
  • Carbon V-Bank Filters: They offer high contamination removal, and are also disposable. Various mediums like cloth, pad, etc., can be used for filtration, but the selection of media depends upon the type of impurities to be removed.
  • Military Carbon Cloth Media: It uses cloth as a media to capture the allergic pollutants, which are trapped by the active carbon.
The problem with these filters is that the pad or the medium needs periodic replacement as it gets clogged. Otherwise, they are cheap, easy to maintain, and effective for removing all types of odors, dust, and other pollutants.