What Is a HEPA Filter and How Does It Work?

Having a bad allergy season? Here's what you need to know.

What Is a HEPA Filter, filter on blue background

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From a stuffy, runny nose to itchy eyes, suffering from allergies is no fun, especially during the spring and summer months. While you might not be able to control your symptoms outside, you can find some relief in your own home. You may be considering purchasing home appliances that have a HEPA filter to absorb airborne allergens and other particles, such as dust and pet hair. 

But do you actually need a HEPA filter? How does a HEPA filter work? Are they really worth the extra cost? Here’s what you need to know.

What Is a HEPA Filter?

HEPA is an acronym for “high-efficiency particulate absorbing filter.” Dr. Hayley Goldbach, MD, board-certified dermatologist and assistant professor of dermatology at Brown University, explains: “In order to qualify as a HEPA filter, it needs to be able to filter at least 99.97 percent of airborne particles with a size of 0.3 microns.”

HEPA filters are capable of removing things like dust, pollen, and mold, as well as some bacteria and viruses.

What Appliances Should Have a HEPA Filter?

“For our house, we made sure that our air filters, HVAC system vacuums both contained HEPA filters since we wanted a high degree of filtration,” says Dr. Goldbach.

She often recommends air filters to her patients to improve indoor air pollution issues. “Choosing an air filter can be overwhelming—size, cost, noise level, type of filter—but a good air filter can dramatically help air quality in a home.”

Keep in mind that once you buy an appliance with a HEPA filter, whether an HVAC system, air purifier, or vacuum, the component still needs to be maintained. “It's important that these filters are replaced on a regular schedule so that they don't become clogged and less effective with time,” she explains. 

Not sure how often you need to replace a filter? Check the owner's manual. If you no longer have it, most manufacturers have them available for free online. If you can’t remember the last time you replaced the filter, that's a good sign it probably needs to be replaced.

Who Needs a HEPA Filter?

“HEPA filters are most important for those who are sensitive to poor air quality. Though air quality affects everyone, some groups are more sensitive,” says Dr. Goldbach. “Examples include people with allergies, chronic lung disease, compromised immune systems, young children, and pregnant women.” 

Even if you don’t fall into any of the above categories, it’s always better to opt for an appliance that has a HEPA filter versus one that doesn’t. 

Is There a Type of Filter That's Better Than HEPA?

While HEPA filters are excellent, other options are available. “There are filters that trap a higher percentage of particles. ULPA filters trap 99.99 percent versus 99.97 percent, for example,” Dr. Goldbach explains. “However, airflow through these filters is less and they are not frequently offered in things like vacuums. A HEPA filter should be sufficient for the average house where the particles you are trying to remove (such as pet dander, pollen, and dust) are large and more easily trapped by a HEPA filter.”

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