Everything You Need to Know About HEPA Filters

The average home environment has more airborne allergens and pollutants than we’d like. Mold spores and pet dander are examples of contaminants that affect the air quality in our homes. If you suffer from allergies, itchy eyes, or persistent coughing, a HEPA air purifier could provide much-needed relief. 

High-efficiency particulate air (HEPA for short) filters remove pollutants from the air and allow us to breathe easier by preventing small, harmful particles such as dust mites, dirt, smoke, pet dander, and pollen from getting into your home’s air ducts. They do this by forcing air to pass through a very fine, mesh-like web of fibers.

In this article, I’ll talk about HEPA filters — how they work and how to care for them.

How HEPA Filters Work

HEPA filters differ significantly from standard home air filters — they’re a relatively thick and dense mat of randomly arranged fibers and are pleated, which allows them to capture particles of various sizes efficiently. They trap contaminants in four ways:

1. Impaction — Larger particles can’t follow the curve of airflow through the filter and embed in the fibers
2. Interception — Particles aren’t able to keep up with airflow through the filter and end up getting stuck on the fibers
3. Diffusion — Pollutant particles bounce around gas molecules and eventually stick to a fiber.
4. Sieving — Relatively large particles get stuck between two fibers when passing through the filter

You’ll see HEPA filters most often in home air purifiers and vacuum cleaners. To qualify as a HEPA filter, the filter must trap 99.97% of pollutants that are 0.3 microns or larger in size. A strand of hair is about 100 microns in width — so the pollutant particles are very small.

A HEPA filter can’t trap gases, bacteria, viruses, or odors, but it can trap substances such as wildfire smoke. Not all HEPA filters meet U.S. government standards — look for the terms “true HEPA” and “absolute HEPA,” which indicate that they do qualify.

How Much Does a HEPA Filter Cost?

HEPA filters vary in cost and range from $16 to $95 depending on quality, estimated longevity, and the manufacturer. Air purifiers that rely on HEPA filters range from $50 to $1,000 depending on size, quality, and projected coverage area. HEPA air purifiers and HEPA filters can be purchased at most hardware, home goods, or big-box stores, as well as online.

How To Choose a HEPA Filter

To produce the cleanest air possible, HEPA filters and the air purifiers they’re used in must suit the space they’re intended to serve, as measured by the CADR (clean air delivery rate). The CADR indicates how much air passes through the filter based on square footage, and some rooms may be too large for the filter to properly clean pollutants from the air. If the fit isn’t right, you won’t get the air purification results you need.

Look for ENERGY STAR-certified air cleaners. They offer significant savings for both your wallet and the environment, and are more energy efficient than models without ENERGY STAR certification. If every room air cleaner sold in the United States carried the ENERGY STAR certification, the resulting energy cost savings would be substantial.

Caring for Your HEPA Filter

HEPA filters have been called the gold standard in air purification. You’ll want to protect your investment by caring for your purification system or air conditioning unit. Replace the filters regularly in your system. Some will need to be changed out every three to six months, while others may last for a year or two. Some manufacturers make units with reusable filters.

You should be able to change your filters on your own. For more information on how to change or clean your air filters, consult the manufacturer’s recommendations specific to your filter.

The Importance of HEPA Filtration

Indoor air pollutants rank among the top five environmental health risks, according to the U.S. Environmental Protection Agency (EPA). Air filtration systems — particularly those using HEPA filters — excel at improving indoor air quality. They’re highly effective at removing pollen, dust, and other harmful particles from circulating air, providing relief for asthma and allergy sufferers.

Using HEPA filter-equipped purifiers can be especially beneficial during peak allergy seasons. Many air purifiers come with programmable timers, allowing you to customize their operation to suit your specific needs. Using equipment with HEPA filters in your home takes a significant step toward creating a healthier and more comfortable living environment.