HEPA filters have been getting a lot of buzz lately, especially with marketing directed toward families whose members suffering from allergies, asthma or other breathing disorders. However, consideration should be given before employing their use.
Filters made for residential HVAC use come in various types, each carrying a specific rating on the MERV scale. MERV, which is short for Minimum Efficiency Reporting Value, is a graduated rating system extending from 1-20, with higher-rated filters able to capture more and smaller airborne particulates. HEPA (High Efficiency Particulate Air) filters fall into the MERV 17-20 range. To be considered “true” HEPA filters, they must be able to filter out 99.97 percent or more of particles 0.3 microns or bigger.
Most new residential HVAC systems come with a MERV 1-4 rated filter installed, capable of filtering particles 10 microns or greater in size. These aren’t intended to maintain air quality but rather are designed to protect system components from the largest dust particles.
Because of its fine filtering capabilities, HEPA filtration is typically used to provide ultra-clean air in medical applications and in computer manufacturing clean rooms. In a residential environment, however, their use is usually limited to air-purifying equipment, vacuum cleaners and in specially designed heating and cooling systems engineered or modified to overcome their substantial airflow resistance. HEPA filters incorporate a random matrix of fibers, usually fiberglass, with diameters of between 0.5-2.0 microns. Three mechanisms – interception, impaction and diffusion – come into play during the HEPA filtration process.
HEPA’s main limitation is its impeding of adequate airflow in typical home HVAC systems. Although they may be used, your system’s air handler likely will need to be significantly modified. It’s best to consult an HVAC professional to explore the practicality and benefits of doing this. The federal EPA recommends MERV 7-13 rated filters for home use, stating they are nearly as effective as HEPA filters at capturing small particles, and considerably less expensive to buy and use.
Since 1951, Ernst Heating & Cooling has been delivering expert HVAC sales and service to our southwest Illinois clients, including those in Alton, Bethalto, Collinsville and Troy. Please contact us with any questions regarding HEPA filtration or other matters pertaining to indoor air quality/comfort.
Our goal is to help educate our customers in Hamel, Alton, Glen Carbon, Highland, Greenville, and Troy, Illinois and surrounding areas about energy and home comfort issues (specific to HVAC systems). For more information about HEPA filters and other HVAC topics, download our free Home Comfort Resource guide.
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