**5.2 Activated carbon air filters**

Also referred to as charcoal-impregnated air filters, these types of filters are used to effectively remove odors and fumes from the air during the air recirculating process.

Commercial activated carbon filters provide high-efficiency odor, fume, and gas removal and are fabricated using the finest quality coatings, including bulk air filter media and pads cut to size, pleats, panels, and high-density granular carbon packs.

Synthetic media substrates, such as non-woven polyester, are impregnated with finely ground coatings, including activated carbon, zeolite, or alumina, and a heat set to retain these coatings even when the activated carbon filter media is rinsed or vacuumed. Just as a sponge soaks up water, the media of activated carbon air filters absorb odors and fumes. Moreover, the odor-causing molecules are permanently removed from the air, rather than simply being masked with a different odor.

The rate of adsorption depends on the relationship between the pore structure, or surface area, and the shape of the contaminating molecules. Activated carbon filters are disposable air filters, and once they have become saturated with odors, fumes, or gases, after approximately 3 to 6 months of use, they must be replaced. The amount of activated carbon required will depend on the amounts of odors, fumes, or gases to be removed [24].

### **5.3 Deodorizing filters**

Deodorizing air filters use acidified titanium, activated carbon, ceramic fiber, pulp, and other advanced materials that are prepared using a variety of rigorous refinement processes. They function by purifying the air and maintaining air fresh and show superior efficacy when used in conjunction with UV irradiation [24].
