Are Air Purifiers Effective? (What You Need To Know)

Due to concerns about the bad air quality in the Philippines, air purifiers have been booming ever since they have been introduced in the market. However, there seems to be a spike in demand now that we’re in the middle of the global COVID-19 pandemic. This begs the question: are air purifiers actually effective against these threats?

To a degree, yes, air purifiers are effective at removing some of the allergens, smoke, and odors present in indoor air. Some are even equipped with technologies that claim to be effectual against viruses and bacteria. With that said, air purifiers should not be treated as a magic pill, and general cleanliness and adherence to safety protocols are still advised.

This article will be an evidenced-based discussion on the efficacy of air purifiers. Read on to learn more.

How air purifiers work

At its most basic form, air purifiers purifies the air by letting it pass through several filters to catch contaminants like dust, pollen, and pet dander. Depending on the types of filters used, and air purifier can also take away Volatile Organic Compounds (VOCs) like formaldehyde and benzene which are present in indoor air.

The filter that does most of the heavy lifting is the High-Efficiency Particulate Air (HEPA) filter as they can trap 99.97% of all particles larger than 0.3 microns. The HEPA filter is made out of a extremely fine materials that is folded into multiple layers. These layers trap the particulate matter while letting the air pass through.

Since HEPA filters act more like a physical barrier, they are ineffective at removing gases, chemicals, and odors in indoor air. That is why HEPA filters are typically augmented with an activated carbon filter to remove these types of contaminants in the air. Activated carbon filters work through adsorption (not absorption), where the molecules in the contaminants stick to the surface of the carbon filter. Both the HEPA and the activated carbon filters eventually fill up with contaminants and will need to be replaced after a few years.

Some air purifiers are also equipped with ionizers the generate positively and negatively charged ions that claim to deactivate viruses and bacteria. They also help suspended particulate matter to drop from the air and into a surface that can be wiped off to clean. However, the jury is still out to the degree of their effectiveness.

What are air purifiers effective against?

Studies show that air purifiers provide a degree of protection against several contaminants present in indoor air. Here are some of the contaminants that they are effective against.

Common allergens

Air purifiers with HEPA filters are touted to be a solution to reduce the presence of contaminants like dust, pollen, and other fine particulate matter (PM2.5) that can cause allergies and asthma. One study shows that air purifiers reduced the levels of PM2.5 present in the air by 43%, which resulted in an improvement in nasal symptoms in children with allergic rhinitis compared to a control group.

Studies also show that air purifiers can also reduce the levels of allergy-causing mold spores present in indoor air, especially if paired with a dehumidifier.


Most air purifiers equipped with a HEPA filter can remove particulate matter from cigarette smoke. In fact, a study shows that air purifiers can reduce PM2.5 from secondhand smoke by 45% after 4 weeks of use.

However, the air purifier must be equipped with an activated carbon filter to remove some of the odor associated with smoke. The keyword there is some, as while studies show that air purifiers with carbon filters do trap odor-causing chemicals within the filter, the heave particles in cigarette smoke tend to fall out of the air quickly and stick to surfaces.

Apart from cigarette smoke, scientists also recommend the use of air purifiers to counter severe negative changes in air quality caused by fires and traffic-related pollution as they can reduce PM2.5 concentrations by 32–88%.


VOCs are organic chemicals that can cause adverse health effects. These contaminants are present in household products like paints, cosmetics, and cleaning solutions. This is why the the level of VOCs is higher indoors than outdoors.

Air purifiers that are equipped with activated carbon filters can also reduce the amount of VOCs in the air. A study shows that carbon filters have a VOC removal efficiency of 20% – 40%. Apart from that, another study shows that an air purifier with an activated carbon filter can remove a 60% – 70% of the ozone from the air after 67 – 81 days. Ozone has negative effects on people exposed to it and are caused by VOCs interacting with Nitrous Oxide (NOx).

Viruses and bacteria

This is where things get contentious. While research shows that air purifiers with HEPA filters do offer a degree of protection against even the smallest viruses and bacteria, they only trap them, and not kill them. Moreover, it does not offer complete protection, as it only captures viruses from the air, which means that viruses that have stuck on surfaces like tables, shirts, and even your skin will not be filtered by the air purifier.

However, there are now air purifiers equipped with ionizers that claim to be effective against certain viruses and bacteria. Ionizers emit negative ions (some brands emit both positive and negative ions) that attach themselves to airborne viruses and make them heavy and thus fall on surfaces. Some brands, like Sharp’s Plasmacluster Ion technology, even claim to inactivate different types of viruses and bacteria by changing their chemical composition.

Are air purifiers effective against SARS-CoV-2 (COVID-19)?

As with the existing research regarding an air purifier’s efficacy against viruses, its effect on the SARS-CoV-2 virus is still contentious.

Most scientists argue that air purifiers may help reduce the amount of airborne SARS-CoV-2 (which causes COVID-19), but they do not offer complete protection. Since air purifiers only clean the air that they can suck, the particles and droplets that have SARS-CoV-2 that have stuck on surfaces will not get purified.

The proximity of the air purifier and the source of the particles should be factored in as well. Meaning, if you are sitting beside the air purifier, and the droplets coming from the person in front of you (who may or may not be infected with COVID-19) will still travel to your general direction before being trapped by the air purifier’s HEPA filter. Hence why adhering to strict social distancing and cleanliness protocols is a must.

Regarding ionizers, some brands have already released their ionizer technology’s efficacy against COVID-19. Brands like Sharp have presented evidence backed by researchers that their proprietary ionizer technology (Plasmacluster Ion) can render 99.7% of the SARS-CoV-2 virus inactive within 40 minutes.


As you’ve seen, research shows that air purifiers do help remove some contaminants in indoor air that can cause adverse health effects to those exposed. With that said, air purifiers should not be used on their own. Proper cleaning and sanitation should be done to improve your indoor air quality.

Air purifiers also help reduce the number of airborne viruses and bacteria in your room. However, do not treat this as a magic shield that protects you 100%. Always adhere to proper safety protocols to prevent the transmission of communicable diseases.

Another point to remind you: if you have respiratory issues like allergic rhinitis and asthma, you should consult with your doctor to help you manage your symptoms.



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