An air purifier with only a HEPA filter captures fine dust, pollen, and bacteria, but does little against volatile substances that you mainly smell: cooking odors, cigarette smoke, paint fumes, pet odors, or exhaust gases coming in through an open window. For this, an activated carbon filter is required. In this article, we explain how that filter works and why it is a valuable addition to HEPA filtration.
What is activated carbon?
Activated carbon (also called activated charcoal) is carbonaceous material, often made from coconut shells, wood, or coal, that has been treated at high temperatures with steam or chemicals. This process creates millions of microscopic pores in the material. As a result, a small amount of activated carbon has a huge surface area: one gram can easily contain hundreds of square meters of surface area. The larger that surface area, the more substances the filter can trap.
Adsorption instead of filtration
A HEPA filter works mechanically: it physically traps particles between its fibers. An activated carbon filter works differently, through a process called adsorption. Gas molecules and odorants come into contact with the carbon surface and "stick" to it in the pores, so to speak. This is how gases and odors are removed from the air, which a HEPA filter simply lets pass through, because they are molecules and not solid particles.
What does an activated carbon filter capture and what does it not?
An activated carbon filter is particularly effective against:
- Cooking and frying odors
- Cigarette and incense smoke (the odor component)
- Volatile organic compounds (VOCs) from paint, furniture, or cleaning products
- Exhaust gases and industrial odors from outside
- Pet odors
However, it does not capture fine dust, pollen, dust mites, or bacteria. For that, a HEPA filter remains necessary. That is also why most serious air purifiers, including the Dynter AirPure Plus PA244, use a combined filter system: first a pre-filter for coarse dust, then HEPA13 for fine dust, pollen, bacteria, and viruses, and an activated carbon layer for odors and gases.
How long does an activated carbon filter last?
An activated carbon filter eventually becomes "saturated": the pores are full, and the filter no longer absorbs new odors. How quickly this happens depends on the amount of odor and gas exposure in the home. In a smoking area or a kitchen where a lot of frying is done, the filter becomes saturated faster than in a quiet bedroom. On average, manufacturers recommend replacing the filter every 6 to 12 months. If you notice that odors are not being removed as effectively, that is usually the first sign that replacement is needed.
Why is this filter important for indoor air?
Many people underestimate how many volatile substances are released indoors: from furniture, paint, cleaning products, and cooking. An air purifier without a carbon filter solves the fine dust problem but leaves that odor and gas load largely untouched. Anyone who has complaints about a musty smell, lingering cooking odors, or odors from outside will often notice a difference once a carbon layer is included in the filter system.
Our advice
Preferably choose an air purifier with multi-stage filtration that includes activated carbon as standard, rather than as a separate accessory to order later. The AirPure Plus PA244 combines a pre-filter, HEPA13 filter, and activated carbon layer in a 4-stage filter system, so you tackle fine dust as well as odors and gases all at once. In our experience, this is the most practical solution for most households.