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HEPA filters vs activated carbon filters: What’s the difference?

Updated on January 25, 2024
Written by
Danny Ashton
Danny is the founder of HouseFresh and has been writing about air purifiers and indoor air quality since 2010. He is our lead tester, conducting all the tests we use to evaluate air quality products. That is why you will always see his name attached to our reviews.

HEPA filters can remove particulate matter and allergens like dust and mold. On the other hand, activated carbon filters can adsorb and remove gases, such as VOCs and filter out smoke and unpleasant odors. 

Both types of filtration are essential for improving indoor air in the home and across different industries. 

Enhanced air quality can benefit your health and well-being, so it’s worth considering using HEPA and activated carbon filters simultaneously.

A crucial part of any decent air purifier is its filtration technology; HEPA and activated carbon are two of the most effective. Yet, as they each filter out different airborne contaminants, how can you tell which would be best for your living space? 

Let’s dive in to explore their differences and benefits.

HEPA filters vs activated carbon filters 

HEPA FiltersActivated Carbon Filters
Used for removing:

💨 Dust and dust mites
🐱 Pet dander
🍄 Mold
🌼 Pollen
🔥 Smoke
🦠 Bacteria
🔴 Other particulate matter  
Used for removing:  

🍳 Odors from cooking & the kitchen
🚬 Smells from cigarette
🌿 Smells from weed smoke
🐶 Pet odors
🚽 Unwanted bathroom smells
🧴 Volatile organic compounds (VOCs)
😷 Chemical fumes and gasses

According to the Environmental Protection Agency, HEPA filters can remove at least 99.97% of airborne contaminants with a size of just 0.3 microns. This means particulate matter (PM) and allergens such as dust, pollen, bacteria and mold — making them highly effective at sanitizing indoor air.

How HEPA filters work

How HEPA filters trap particles resembles how a spider’s web catches prey: 

  • Stage 1: Fan draws in the air.
  • Stage 2: An assortment of randomly organized fibers catch and trap a range of particle sizes. When captured by HEPA filters, the particles go through four stages: diffusion, interception, impaction and sieving.
  • Stage 3: Cleaner, healthier air is pushed back into your space.

There are different types of HEPA filters: Classic HEPA, True HEPA, and Medical-Grade HEPA. Each of them has a different grade of filtration efficiency, meaning they will deal with differently-sized particles:

There have been various scientific studies looking into the effectiveness of HEPA filters: 

📖 HEPA air purifiers can significantly reduce house dust mite concentrations in indoor air. (Source: Asian Pacific Journal of Allergy and Immunology)

📖 HEPA filters can reduce particulate matter concentrations in the home by up to 50%. (Source: American Academy of Pediatrics)

📖 HEPA filters can help to improve at least one allergy and/or asthma symptom in sufferers. (Source: EPA)

📖 Asthma symptoms in children eased when a HEPA purifier was utilized in their bedroom. (Source: Current Allergy and Asthma Reports)

📖 HEPA purifiers can decrease the chance of pathogens being transmitted through the air. (Source: NHS)

📖 HEPA air cleaners can mitigate exposure to the virus that causes COVID-19 when combined with effective mask-wearing. (Sources: Centers for Disease Control and Prevention & Manchester University)

While HEPA filters are fantastic at removing harmful particles, they can’t remove odors and gases like volatile organic compounds (VOCs). This is where activated carbon filters come into their own. 


If you want to read more about HEPA filtration, you should head over to our article about how HEPA filters work and our guide to the best hospital grade air purifier on the market right now.

How activated carbon filters work

Activated carbon filters out gaseous pollutants like VOCs and smells, including cooking and smoke.

They do this through a process called adsorption. Unlike absorption, adsorption means contaminants stick to the carbon surface’s outside and become trapped:

  • Stage 1: Once air enters the purifier, it passes through the activated carbon filter.
  • Stage 2: The adsorption process traps odors and VOCs
  • Stage 3: Clean air flows out of the activated carbon filter and back into the room


Interested in learning more about the adsorption process? Check out our article, which breaks down how an activated carbon filter works in more detail.

The amount of activated carbon within the filter is essential, as the more carbon it contains, the more effective it will be at trapping contaminants. 

Remember that carbon filters can become saturated and wear out fairly quickly, giving them a short lifespan. HEPA filters, however, are generally more durable and affordable. 

As we’ve seen, activated carbon filters can effectively remove unpleasant odors, gaseous pollutants and chemical fumes, making them ideal for home and work environments. But what does the science say? 

📖 Activated carbon effectively removes gaseous pollutants. Specifically VOCs, and enhances indoor air quality. (Source: University of Bhubaneswar)

📖 Activated carbon is one of the best forms of air purification due to its substantial adsorption capacity. (Source: University of Reading)

📖 Adsorption is one of the most preferred methods of air purification as it doesn’t contain any by-products. Additionally, activated carbon is effective due to its “high microporous volume,” i.e., the amount of microscopic pores, which facilitates adsorption. (Source: Global Challenges in Energy and Environment, Select Proceedings of ICEE 2018 (pp.65-75))

📖 Certain types of activated carbon can potentially remove VOCs from indoor air. This is due to their “high adsorption capacity at low water vapor pressures.” (Source: Carbon Trends)

Final thoughts

To wrap up, HEPA and activated carbon filters are essential for air purifiers as they eliminate different pollutants. 

HEPA filters are necessary if you’re worried about allergens and particulate matter. If you want to reduce odors and VOCs, activated carbon is your best bet. 

However, if you’re concerned about all of the above, using a purifier with HEPA and activated carbon filtration is recommended. 


About the author

Danny Ashton

Danny is the founder of HouseFresh and has been writing about air purifiers and indoor air quality since 2010. He is our lead tester, conducting all the tests we use to evaluate air quality products. That is why you will always see his name attached to our reviews.