By Glenda Taylor and Bob Vila | Updated Apr 29, 2021 11:46 AM

Few things are as important as the air we breathe. One of the most popular products available in the ongoing quest for cleaner air—especially for allergy sufferers—is the high-efficiency particulate air (HEPA) filter found in a number of air-cleaning products. If you’re considering buying an appliance with built-in HEPA filtration, keep reading to understand what these filters can (and can’t) do to help improve the air quality in your home as well as what you’ll want to look out for when buying a HEPA air purifier.

HEPA filters were designed in the 1940s to protect workers in nuclear facilities from breathing radiated airborne particles. By the 1960s, HEPA filters were being used in hospitals to help stop the spread of airborne germs and particulates, and soon after they began to appear in household appliances, including vacuum cleaners, air purifiers, and whole-house air-filtration systems. The Energy Star branch of the Environment Protection Agency (EPA) defines HEPA filters as being able to “remove more than 99 percent of all airborne pollutants 0.3 microns or larger.” A micron is a microscopic particle, less than 1/25,400 of an inch long.

For asthma and allergy sufferers, air filled with dust, pollen, and dander can lead to respiratory symptoms, such as sneezing, watery eyes, sore throats, and trouble breathing. Fortunately, the airborne particulates that trigger allergy symptoms are relatively large in size and are easily trapped by a HEPA filter. According to the EPA’s Guide to Air Cleaners in the Home, using HEPA air filters in portable air-purifiers and HVAC systems can help reduce allergy and asthma symptoms. Currently, however, the EPA has no formal recommendations for the use of HEPA filters in the home.

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Because allergens enter the home through open doors and windows—a single drafty window can let in millions of airborne particulates—using HEPA filters can’t guarantee the removal of all allergens. In addition, HEPA filters can’t remove the risk of all inhalable pollutants, including:

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The Department of Energy (DOE) specifies HEPA filters used by DOE contractors must be able to remove 99.7 percent of airborne particles 0.3 microns and larger, but no federal or national regulations exist for the consumer industry. Manufacturers of high-quality HEPA filters voluntarily test and certify their filters to meet DOE standards, labeling them as either “Absolute HEPA” or “True HEPA.” Manufacturers whose filters do not meet DOE specifications are often labeled as “HEPA-type,” “HEPA-like,” or “HEPA-style.” While they may be good filters, they haven’t been tested and certified as meeting DOE standards for HEPA filters.

The three most common home appliances to make use of HEPA filters are whole-house filtration systems designed to treat entire HVAC systems, portable air purifiers, and vacuum cleaners. For homes with family members who suffer from asthma or allergies, using one or more of these appliances may be helpful in alleviating allergy symptoms.

Because dense HEPA filters trap most of the particulates in the air, they tend to become clogged more quickly than traditional filters. While the recommended replacement rate varies from appliance to appliance and depends on how much air is being drawn through the filter (and how dirty the air is), you can expect to change HEPA filters at least twice as often as you would change non-HEPA filters. This can be expensive, as a replacement filter for a standard vacuum runs approximately $10, while a replacement filter for a HEPA vacuum runs around $50.

The ability to clean a HEPA filter saves money. While filters differ and some are difficult to clean without damaging them, users may be able to eke out an additional few months or longer by cleaning a HEPA filter.

The cleaning process will remove built-up dirt, dust, and pollens from the filter while minimizing damage to its delicate accordion folds. Rather than sticking a HEPA filter under a running faucet, which is almost guaranteed to damage the filter as the water pressure makes contact with the delicate folds, the best way to wash a HEPA filter is by submerging it.

With the arrival of the novel coronavirus, COVID-19, medical researchers and scientists have been working on ways to reduce the airborne spread of the virus. According to the Centers for Disease Control (CDC), COVID-19 particles are about 0.1 microns in size. Normally, this would be too small for a HEPA filter to trap since the filter traps particles only as small as 0.3 microns in size.

Fortunately, COVID-19 particles don’t travel through the air alone—rather, they’re attached to tiny respiratory droplets that are exhaled when infected humans cough, talk, or sneeze. A HEPA filter will trap these larger, human-generated droplets and, in doing so, can trap COVID-19 particles as well.

In the quest to control COVID-19 and reduce airborne transmission rates, air purifiers fitted with HEPA filters may play a role when used in homes and public settings, such as waiting rooms. Users should not assume that an air purifier equipped with a HEPA filter will entirely protect them against becoming infected. However, in conjunction with other precautions, such as wearing masks, washing hands frequently, and social distancing, HEPA-fitted air purifiers may help reduce the risk of infection.

Before buying an air purifier to help clean the air in a home, find out how to set it up and use it most effectively.

Air purifiers don’t come with a lot of complex features, so they’re relatively self-explanatory right out of the box. However, for the best results, take some time to ensure the new purifier is set up correctly.

A couple of usage tips, will help users get the best air-cleaning results from an air purifier.

The part of an air purifier that requires the most attention and maintenance is the filter. Most purifiers come with more than one filter, including pre-filters that block odors and some VOCs. Other pre-filters block larger airborne particles to keep a HEPA filter from clogging as quickly.

Air purifiers are rated by the amount of air they circulate, known as the clean air delivery rate (CADR). Clogged filters will reduce the machine’s efficiency so they should be regularly inspected—once a month, cleaned (as described above), or replaced with new filters.

Users can optimize the effectiveness of a home air purifier by following some tips:

When the air purifier is working as intended, it will reduce the amount of pollutants in the room, but users may question if it’s working as well as it should. The following three steps will help determine if the purifier is doing its job.

In homes where clean air is essential, it’s critical to keep the air purifier clean. At least once a month, it’s a good idea to clean the unit, but before you start, anyone in the home who has allergies should leave the room because the cleaning process may release pollutants into the air.

Air purifiers do a beneficial job of removing pollutants, but users should take additional steps to keep indoor air clean.

Breathing contaminated air is a nuisance for many but can be a health hazard for those who suffer from asthma or allergies. According to a study published in the Journal of Asthma, when air purifiers were placed in homes with children who suffered from asthma symptoms, after just 12 weeks, they felt better and showed fewer signs of respiratory problems.

Not all air purifiers clean the air equally—some, such as those with HEPA filters—are more efficient than others, some are designed for large or small rooms—and others might actually be hazardous to health.

Consider the following factors when shopping for a HEPA air purifier.

Clean air is a goal of many, but airborne pollutants are virtually everywhere. For those looking to reduce allergens, dust, and other airborne contaminants in the home, a few questions are to be expected.

Yes, by using HEPA filters in both vacuums and air purifiers, the user can reduce the number of airborne allergens and pollutants in a home.

A HEPA filter labeled “True HEPA” or “Absolute HEPA” has been tested and meets the criteria for being highly efficient.

A whole-house HEPA air purifier attaches to the main trunk of a home’s HVAC intake duct and filters out harmful pollutants every time the furnace or AC is operating. Replacement HEPA filters for this type of purifier are the most expensive and can run $50 to $110.

Currently, HEPA filters are considered the top filters for removing airborne particles, such as mold spores, dust, dander, and pollen. They don’t, however, remove odors and some types of VOCs. By purchasing a HEPA air purifier that contains additional filters, such as a carbon filter and a pre-filter, the unit will remove a maximum amount of airborne pollutants.

When used in both air purifiers and vacuums, HEPA filters offer the best shot at cleaning indoor air. Other steps, however, such as keeping windows closed, not having houseplants, and laundering draperies regularly, are also necessary for reducing the number of airborne pollutants in a home.

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