Theoretically, we can remove almost all particulate matter from the air stream. However, we are now faced with the problem “how the gases and vapours be removed?”
HEPA filtration is effective down to the .3 micron range and will remove some particulates smaller than .3 microns. Yet, chemical pollutants like gases and vapors are .01 microns or even smaller. Very simply, particulate filters do not, and cannot, remove material that is this small and is a gas. If particulate solutions cannot use to remove gases, what can we do to remove them?
For HVAC applications, where the concentrations are very low and the contaminant loading varies from sizes to sizes, adsorption has shown itself the most effective and the economical means for removing gases.
Adsorption with activated carbon is thus a commonly seen process in applications such as gas masks, space capsules, nuclear plants and so forth, in which the removal of gases is highly needed.