HEPA Filtration and How It Differs From the Standard Mechanical Air Filter

HEPA filtration is typically used for providing ultra-clean air for medical facilities, computer manufacturers, pharmaceutical companies and other businesses that need “clean rooms.” For residential use, HEPA filtration is typically limited to air-purifying equipment and vacuum cleaners, although it may be employed in forced-air residential HVAC systems if these systems are modified to utilize these special filters. This may be needed in homes with occupants suffering from severe allergies or asthma or certain breathing difficulties.

HEPA (High Efficiency Particulate Air) filters aren’t recommended for use in most home heating/cooling systems because their design causes significant reduction in airflow delivery, which most residential systems aren’t able to handle. Consequently, using HEPA filters in equipment not designed to overcome their inherent airflow resistance can damage the equipment and will provide unsatisfactory indoor air quality and conditioning.

HVAC air filters are rated on a graduated scale from 1-20, with each number indicating the minimum sized particle the rated filter can effectively capture. The rating system, known as MERV (Minimum Efficiency Reporting Value), works as follows:

• MERV 1-4, filters particles 10 microns or larger
• MERV 5-8, filters particles between 3-10 microns
• MERV 9-12, filters particles between 1-3 microns
• MERV 13-16, filters particles between 0.3-1.0 microns
• MERV 17-20, filters particles smaller than 0.3 micron

MERV 17-20-rated filters are defined as HEPA if they meet the government standard of filtering a minimum of 99.97 percent of all particles 0.3 microns or smaller in size. They are able to do this due to their unique construction of a random, web-like matrix of fibers, usually fiberglass, which attracts and grabs onto particles coming near them.

Standard mechanical filters act more like a sieve, with the size of their surface pores determining the size particles they capture. The spaces between the fibers used in HEPA filtration are substantially larger than the particles they’re able to filter out, but through the principles of interception, impaction and diffusion, provide extremely fine filtering capabilities.

Energy 1 Heating & Air Conditioning has been serving clients in the Lorain, Elyria and Oberlin areas of Ohio for 30-plus years. Please contact us for information/advice on choosing the right air filter or any home air comfort concerns.

Our goal is to help educate our customers in Lorain, Ohio about energy and home comfort issues (specific to HVAC systems).  For more information about HEPA filtration and other HVAC topics, download our free Home Comfort Resource guide.

Image courtesy of Shutterstock