What Is a HEPA Filter?

Carpet vaccum cleaner

didesign021 / Getty Images

HEPA is an acronym for high-efficiency particulate air. HEPA is a type of filter that can trap a large number of very small particles that other vacuum cleaners would simply recirculate back into the air of your home. HEPA vacuums are recommended for minimizing dust, dander, and other common allergens in homes where people suffer from allergies and respiratory conditions. The fact that a filter or vacuum bag says "HEPA," however, doesn't mean you're getting true HEPA performance.

True or Absolute HEPA Filters

True or absolute HEPA filters must be tested and meet a specific standard to be considered true HEPA. True HEPA filters have a serial number assigned to them and have been proven to trap at least 99.97 percent of particles of 0.3 microns. Look for the test results since they should be printed on the filter. True or absolute HEPA filters may be more expensive than other "HEPA" filters, but they must perform at a certain standard to receive the distinction of true or absolute HEPA.

HEPA-Type Filters

HEPA-type filters may be made in similar ways to true HEPA filters and may even resemble them. However, they do not have to meet the same standards as true or absolute HEPA filters. Many filters sold as HEPA may capture only 85 to 90 percent of all particles, and that percent can fall even lower for particles of one micron and below. These filters will not have serial numbers.

The Difference Between True and HEPA-Type Filters

Look for the serial number and test results printed on true or absolute HEPA filters. Make sure that the test results at 0.3 microns are 99.97 percent or above. The size of 0.3 microns is the testing standard because most filters will perform better with both smaller and larger particles. Also, most household allergens are 0.3 microns or larger.

It's important to note that a HEPA vacuum is designed for HEPA performance and may be either a bagged or bagless model. In other words, it's not the bag that makes a vacuum HEPA. It's also important to understand that simply using a HEPA-type bag—or adding a HEPA filter—in a standard vacuum does not mean you'll get true HEPA performance. HEPA vacuums are sealed and have special filters that clean all of the air going out of the vacuum. Standard vacuums usually filter the outgoing air via the vacuum bag.

In commercial environments where HEPA vacuums are required, such as construction or restoration sites, using standard vacuums with HEPA filters or bags may constitute a violation of EPA rules and may result in a substantial fine.

Do HEPA Filters Reduce Allergic Reactions?

There have been surprisingly few studies conducted to evaluate the impact of HEPA filters or other air-filtering devices on allergic symptoms. As a result, while it is fair to say that true HEPA filters do remove certain elements from the air, it's not clear what impact that will have on your allergies. The bottom line: HEPA filters do a great job of cleaning, and they certainly can't injure you or your surroundings. On the other hand, they may have little or no impact on your symptoms.

How to Buy a HEPA Vacuum

True HEPA vacuums are widely available and are not necessarily more expensive than comparable standard vacuums. You can research and buy them just like any ordinary household appliance. Once you've confirmed that a vacuum is true HEPA, you can make your selection based on the usual factors, such as type, price, performance and convenience features, brand reputation, etc.

Fun Fact

Consumer Reports found that HEPA vacuums they tested tend to do a good job at removing pet hair, a bonus for allergy sufferers.