The science

Many people know what it feels like to step outside and experience poor air quality—your throat feels irritated, there may be an odd odor—but even moderate or mild pollution can have an impact on your health. Americans spend an average of 90% of time indoors, and research shows that indoor air can be 2-5 times more polluted than outdoor air. While many pollutants can be eliminated by getting rid of the contamination source or improving ventilation, air filtration can also play an important role in cleaning our indoor air.

Many building materials, furniture, household appliances, cleaning supplies, and natural substances like dust, pet dander, and mold can negatively affect indoor air quality. Research suggests poor ventilation, chemical-laden household products, rising temperatures, and increasing humidity are exacerbating the quality of our air at home even further. This is where  air purifiers—which many of us relied on in the height of the COVID-19 pandemic—come in.

With indoor air pollutants, there are two main categories to focus on, according to Robert Kachko, ND, LAc, Director of Integrative Health at the Atria Health Institute: 

Particulate matter (PM) is a mixture of solid and liquid particles that come from dust, dirt, soot, smoke, and other pollutants. 

  • Larger particles are categorized as PM10, which means they are 10 micrometers or smaller. Finer—and therefore more dangerous—particles are known as PM2.5, which are 2.5 micrometers or smaller. 
  • These smaller particles can make their way into our lungs and blood stream, where they can cause or exacerbate asthma, allergies, and chronic obstructive pulmonary disease (COPD), and contribute to an increased risk of heart disease, stroke, cognitive decline, Alzheimer’s disease, Parkinson’s disease, and lung cancer.

Volatile organic compounds (VOCs) are gases emitted by certain products, including paint, varnishes, caulk, adhesives, carpeting, disinfectants, pesticides, some cosmetics, gas and wood stoves, dry cleaning, and more. 

  • In the immediate term, these can irritate the eyes, nose, and throat, and cause headaches, nausea, and dizziness. 
  • In the long term, some VOCs can affect the central nervous system, cause kidney and liver damage, and have been linked to diabetes, cancers, and neurological disorders, including Parkinson’s and multiple sclerosis.

The potential benefits

It’s well established that air purifiers can improve the quality of indoor air. While this is potentially helpful for all people, it’s especially true for vulnerable groups, such as people with respiratory conditions.

Studies, especially those examining the use of HEPA filters, have shown reduced infection risk and modest improvements in cardiovascular health and allergy symptoms when indoor air is properly cleaned. People using HEPA filters report fewer asthma and COPD symptoms, less need for allergy medications, small blood pressure improvements, and improved sleep quality and duration. Much of this research involves small sample sizes and short timeframes, so longer-term studies are needed.

Experts in environmental pollutants also note that air purifiers can help reduce exposure to microplastics and chemicals that have been linked to cancers, Parkinson’s disease, and other conditions.

Usage guidelines

There are many kinds of air cleaners, more commonly called air purifiers. Here are the filters to look for:  

  • HEPA, or “high efficiency particulate air” filters theoretically remove 99.7% of particulate matter that could be of concern. This means true HEPA filters will take care of most dust, pollen, pet dander, mold, bacteria, and other particles in the air. They will also remove some microplastics, but they are not effective at filtering most VOCs, as gaseous particles are much smaller than PM.
  • Activated carbon filters absorb gases, odors, and other VOCs, but not particulate matter. Note that air purifiers need a substantial amount of activated carbon to avoid becoming saturated, so make sure to check how much carbon is in your air purifier. A 2023 study found 190-370 g of activated carbon is needed for clean indoor air and up to 1.1 kg is needed to last 30 days in typical indoor air, so make sure to check how much carbon is in your air purifier.
  • Combination filters marry these filter methods to clean both types of contaminants, and those combined devices are what Atria’s experts recommend. (See below for specific recommendations!)

Things to keep in mind

The efficacy of any air purifier depends on using it properly. Here are guidelines to ensure your air filter is as effective as possible:

  • Choose the right size air cleaner for your space. Most portable air purifiers will come with instructions on the size space they are meant to serve. For particle filters, look at the clean air delivery rate (CADR), or how many particles it can clean, and match it to a square footage chart like this one from the U.S. Environmental Protection Agency.  
  • Change the filters regularly. Follow the manufacturer’s instructions on when to change air filters, as old filters will not block pollutants effectively.
  • Don’t block airflow around the device. Place the air purifier in a relatively clear area of the room (not behind a couch or in a tight corner) so it can access as much air as possible. If you have a ceiling fan, turning that on can improve airflow and help eliminate dead spots the purifier might have a hard time reaching.
  • Avoid ozone. Some air cleaners include ionizers, UV lights, or other disinfection features that can emit ozone. Experts do not recommend these because ozone can harm human health.
  • If you’re concerned about indoor air pollution, try an indoor air monitor or hire an expert to test the air in your home. Air quality monitors can provide general trends about the air quality in your home. There are also companies that can test indoor air for environmental exposures, which can tell you more about which contaminants to focus on removing.

Product recommendations

Portable air purifiers: Kachko and Dr. Daniel Angerbauer, a preventive medicine physician at the Atria Health Institute, both recommend Austin Air as their preferred brand for air purifiers due to the available science about these products. They also cite IQAir as another great option that has a wider selection of products to choose from. 

HVAC and furnace systems: If you have a home with central HVAC, you can use the system’s filters to supplement portable air purifiers. Kachko recommends upgrading to a Minimum Efficiency Reporting Value (MERV) rating of at least MERV 11 and ideally MERV 13 or as high as your system can handle. These filters will vary depending on your system and can be purchased at most hardware stores. 

Indoor air quality monitors: Dr. Angerbauer recommends IQAir’s monitors, with PurpleAir and Awair also offering good options. None of these monitors are perfectly accurate, but they can be helpful for showing trends in your indoor air quality and can alert you when contaminants increase, such as when painting a room or frying food on the stove.

While many of our everyday activities contribute to the air pollution in our homes, the good news is that air purifiers and filters are quite effective when used properly. When you’re thinking about a filter, remember the bottom line: make sure to choose a purifier that targets the type of contaminants you’re most worried about, that fits your space, and that you will use daily.