Activated Carbon Air Filters
What is an activated carbon filter?
Carbon, which is often referred to as "charcoal," is a substance that has a long history of being used to remove chemical impurities. Activated carbon is carbon which has a slight electro-positive charge added to it, making it even more attractive to negatively charged chemicals and impurities. There are two principal mechanisms by which activated carbon removes contaminants: adsorption, and catalytic reduction (a process involving the attraction of negatively-charged contaminant ions to the positively-charged activated carbon).
Activated carbon is made by burning hardwood, nutshells, coconut husks, and other carbon-based materials at very high temperatures with steam in the absence of oxygen. This process removes any non-carbon elements from the source material and creates a porous internal structure that provides huge surface area. 5 grams of high quality activated carbon can have an adsorption surface area greater than that of a football field. The best activated carbon is made from coconut husk, and it is ideal for the removal of odorous compounds, gases from volatile organic compounds, and gases of low molecular weight from the air.
Activated carbon filters is used in both air purifiers and water filters. The two most important factors affecting the efficiency of activated carbon filtration are the amount of carbon in the unit and the amount of time the contaminant spends in contact with it. The more carbon the better. Similarly, the more time that contaminants will be in contact with the carbon, the more adsorption that will take place. Air purifiers containing only activated carbon are very rare. Activated carbon filtration is generally found as a secondary treatment method in better quality HEPA air purifiers where it offers enhanced odor and chemical reduction.
What contaminants do activated carbon filters remove?
Activated carbon filters remove/reduce most organic odors and fumes from cooking and household cleaners, as well as many volatile organic chemicals (VOC), pesticides and herbicides. It is also effective at removing chlorine, benzene, trihalomethane (THM), radon, solvents, and hundreds of other man-made chemicals from the air.
Benefits of Activated Carbon Filter Technology
- excellent odor reduction
- best technology for removing chemical contaminants
- well regarded in scientific and medical communities for its effectiveness
- cost effective to purchase, maintain, and operate
Negatives of Activated Carbon Filter Technology
- since it is combined with HEPA filtration, requires fan to provide airflow - fan creates background noise
- filters require periodic replacement
- effectiveness depends on amount of carbon media (more is better)
What to Look for in an Activated Carbon Filter
First and foremost, you should look for a filter with a large volume of activated carbon. Contaminant reduction with activated carbon is directly related to the contact time between the contaminant and the carbon media. Many lower quality air purifiers containing activated carbon contain only a very small amount of activated carbon media (a couple of pounds). These systems do not perform nearly as well as systems containing larger volumes of carbon.