Understanding the Science Behind HEPA Filters

When shopping for a vacuum filter, it’s important to look at the filter’s Minimum Efficiency Reporting Value (MERV), which measures the overall efficiency of the filter. The MERV scale ranges from 1 to 20, and filters with higher ratings not only remove more particles from the air, they also remove particles as small as 0.3 micrometers. HEPA (High-Efficiency Particulate Arresting ) vacuum filters are great choices for allergy sufferers because the filter is designed to catch air-borne particles like pollen, dust mite and pet dander which can aggravate allergy and asthma symptoms, especially in children. To qualify as a HEPA filter, an air filter must remove 99.97% of all particles greater than 0.3 micrometers (3 microns).

HEPA filters are composed of a mat of randomly arranged fibers, typically made out of fiber glass. HEPA filters are designed to target incredibly small pollutants and particles (and can often be used in medical applications because of that). These particles are trapped (they stick to a fiber) through a combination of the following three mechanisms:

1. Interception—particles in the air stream come within one radius of a fiber and adhere to it

2. Impaction—larger particles are unable to avoid fibers and are forced to embed in one of them directly

3. Diffusion—the smallest particles are delayed in their path through the filter, raising the probability that the particle will be stopped by either interception or diffusion.

Some vacuum cleaner filters will be marketed as "HEPA-like," which uses a similarly constructed filter but isn’t as efficient. “HEPA-like” filters do not have to meet the same standards as real HEPA filters and often only capture 85-90% of airborne particles. That percent can fall even lower for particles of 1 micron and below.

However, in order for a HEPA filter to be effective, your vacuum cleaner design must ensure that all the air drawn into the machine is expelled through the filter, and none of the air leaks out. This is known as a “Sealed HEPA" or a “True HEPA.” Vacuum cleaners simply labeled “HEPA” have a HEPA filter, but it doesn’t automatically mean it’s a sealed design and some of the air that passes through the vacuum will not go through the filter, leaving air pollutants behind.

Because HEPA filters are extra dense (to make sure they trap all air-borne contaminants), HEPA vacuum cleaners require more powerful motors and will usually cost more. Newer HEPA filter models are washable, and although this means they may cost more upfront they have to be replaced less frequently.

HEPA filters are so proven at removing airborne particles from the area that they are used in biomedical applications to help prevent the spread of airborne bacterial and viral organisms. They are also used by most airlines to keep recycled air on the planes clean. If you are looking for a filter that can practically guarantee the air you’re breathing is 100% free from pollen, dust mites and other pollutants, a HEPA filter is as good as it gets.

About the Author

TotalVac (http://totalvac.com) is a leading online retailer of vacuum cleaner parts and supplies. TotalVac also carries a large selection of humidifier filters, electric shaver parts, small appliances and appliance parts. Choose vacuum cleaners from top brands such as Miele vacuum, Dyson vacuum, Roomba vacuum and others. If you are shopping for vacuum bags, TotalVac offers a wide selection of vacuum bags, including Kirby vacuum bags and Oreck vacuum bags.