Do Air Purifiers Really Work?

I live in a region prone to wildfire smoke, so I was interested in finding out if air purifiers actually help with that. It turns out that they do. They can also help alleviate asthma and allergies by removing dander, dust, mold spores and other airborne particles.

“But most air purifiers don’t kill bacteria and viruses,” says HVAC and indoor air quality expert Jon Gilbertsen. “Disinfection is not the air purifier’s responsibility, unless it has added features like UV-C light or plasma technology.”

And even then, most of those have not been tested in real-world living conditions, or on humans, so their effectiveness remains murky. Here’s more about how air purifiers work, how well they clean the air and how to maximize their effectiveness.

How Air Purifiers Work

Air purifiers pull air through filters, with the help of a fan, to capture particles like dust, pollen, dander and smoke. Some use ionization and UV light, while others rely on HEPA filtration (high efficiency particulate air).

“Air can clean itself a little over time, but very slowly and never fully, which is why allergens and pollutants tend to hang around,” says Gilbertsen. “An air purifier just speeds the process up and makes it more effective.”

Some are also designed and/or marketed to help prevent respiratory viruses, such as COVID-19 and influenza. Those rely on an expanded base of technologies, which sometimes include generating gases and chemicals intended to kill microbes, such as ozone, formaldehyde and hydroxyl radicals.

How Effective Are They?

Air purifiers can be very effective at removing allergens and helping alleviate asthma conditions, especially those from reputable brands certified by an independent testing agency, such as the Asthma and Allergy Foundation of America (AAFA).

“But air purifiers are about cleaning, not sanitation, so don’t buy one expecting it to keep you from catching the flu,” says Gilbertsen. “It most likely won’t.

Lack of Human Testing

According to a review of nearly 700 studies, which was published in the journal Annals of Internal Medicine, the vast majority of air purifiers claiming to prevent the spread of airborne diseases have not been tested on humans. Instead, most have only been tested in unoccupied rooms, which is potentially problematic because it doesn’t demonstrate how well the purifiers work in real-world scenarios, such as in a home with children running around.

A second potential problem of air purifiers intended to curb the spread of indoor infections is that there have been very few studies concerning their possible harmful effects, such as releasing ozone, formaldehyde and other chemicals into the air.

Effectiveness Against Disease

No air purifiers in the US market have clinical proof of general disease prevention, says air purifier manufacturer Edwin Cheung. That doesn’t mean that they won’t help prevent disease, but don’t rely on them to do so.

“While air purifiers can reduce the number of airborne particles and lower exposure to viruses or bacteria, it’s best if they’re viewed as a layer of protection and not the only method,” says HVAC expert Michael Bilotti.

How Do I Know If I Need an Air Purifier?

You should consider an air purifier if:

• Someone in your home has allergies, asthma or other respiratory issues;
• You have pets, which spread dander and odor;
• You live where there is poor outdoor air quality, such as in a city or area prone to wildfire smoke;
• You use an indoor fireplace or wood stove;
• Your house generally just feels stuffy, dusty or musty.

“Even one of these is already a good reason to use an air purifier,” says Gilbertsen.

Does Room Size Matter When Choosing An Air Purifier?

Yes. Air purifiers are designed for specific room sizes, and if you buy one that is too small, it won’t be as effective. Also, check the purifier’s power rate, which is measured in CADR (clean air delivery rate), which determines how quickly it can filter particles from an area.

“An air purifier that’s bigger than you need will work fine and even faster, but it will also be noisier and more expensive,” says Gilbertsen.

Does It Matter Where You Put an Air Purifier?

Yes, where you place an air purifier in a room matters. “The ideal location for an air purifier is inside the room where airborne pollutants typically frequent,” says Cheung. “We also advise our customers to keep in mind clearance requirements. Some air purifiers can be placed near walls, while others require more space around them.”

Gilbertsen also recommends picking an air purifier that you like the look of. “Otherwise, you’ll want to hide it and end up placing it somewhere in the corner or behind furniture,” he says. “A lot of people do that trying to keep it out of view, then it ends up cleaning the same little pocket of air instead of circulating through the whole room.”

What types of filters do air purifiers use?

Most quality air purifiers use a combination of filters, including HEPA and carbon. HEPA helps remove particles, while carbon helps with issues like gases and odors. It’s also common for air purifiers to have pre-filters, which catch bulky materials like pet hair.

FAQ

How often do I need to replace filters?

It depends on manufacturer recommendations and whether you have pets or live in a high-pollution area, but usually six to 12 months for HEPA filters and three to six months for carbon ones. It’s best to stay on top of the replacing them, as clogged filters reduce airflow, and thus diminish the air purifier’s effectiveness.

“Each home has different conditions, so it’s best to check the filter from time to time for dust buildup, and replace or wash it as soon as it starts looking clogged or dark gray,” says Gilbertsen. “That’s why I recommend investing in a model with a filter-change indicator light.

Do air purifiers help with allergies or asthma?

Yes. Quality air purifiers that are certified by independent testing organizations can help with allergy and asthma symptoms, which are triggered by airborne irritants. Make sure to buy one with the correct size and CADR rating for your room’s size.

“Removing allergens like pollen, pet dander and dust, purifiers can reduce triggers and help people breathe better,” says Bilotti. “While they don’t cure allergies or asthma, they can significantly decrease symptoms when used consistently.”

About the Experts

• Jon Gilbertsen is an indoor air quality expert, HVAC professional and president at Chris Heating & Cooling in the Chicago area, a family run business founded in 2005.
• Michael Bilotti is an Army vet turned HVAC pro with more than 20 years of experience. He is now leading the charge at Degree Heating & Cooling as the general manager.
• Edwin Cheung is founder of Rabbit Air, a two-decades-old air purifier company dedicated to improving health and wellness one breath at a time.

Sources

The Conversation; “Most air cleaning devices have not been tested on people − and little is known about their potential harms, new study finds.” (August 25, 2025).

The post Do Air Purifiers Really Work? appeared first on Family Handyman.

Article source here: Do Air Purifiers Really Work?