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A Guide to Buying a Home HEPA Filter for Heat or Air

Updated on June 26, 2012

Understanding a HEPA Air Conditioner Filter

Air filtration affects everyone's lives, whether it is at home or work and can cause health concerns through particles floating in the air. It is particularly important in environments that are indoors and where the air is conditioned whether it is for comfort, manufacturing conditions or offices.

Particles are generated by every day human activity and this can vary from 100,000 particles per cubic foot for sedentary people to 30 million articles per cubic foot where there is moderate activity like in manufacturing areas. Particles are measured in microns, which is millionth part of a meter. The human hair varies from 50 to 100 microns, and particles that do cause health problems would be much smaller than that. This could be household dust, pollen, mold, pet dander, viruses and bacteria besides tobacco smoke.

A HEPA air filter or high efficiency particulate air filter is designed to be 99.97 percent efficient in removing particle sizes of 0.3 micron size. This could take care of most of the particles that can affect health, though additional precautions may be needed in case of viruses and bacteria. For sterile conditions, HEPA filters may have to be augmented by other devices like ultra violet light.

How Do HEPA Air Filters Work

It is not straining action alone that works when air is passed through a HEPA air filter. Initially when the air comes in contact with the pleated filter media that makes up the filter, this airflow is broken up into smaller air streams with lesser velocity. Particles that are bigger than the pores of the filter media get trapped in it by impaction throughout the body of the HEPA filter. Smaller particles get trapped by diffusion as they travel from areas where the airflow is greater to low airflow areas where particles may already be trapped. If a particle has a negative charge it can also get attracted to the fiber that has a positive charge. Gravity and sieving can also affect particles so that they get trapped in the filter media of the HEPA filter.

Costs and Maintenance

Filters in a HVAC system can also extend the life of a system as the heating or cooling coils are kept clean and thus are able to operate at the desired efficiency. MERV is an industry standard that measures the ability of air filters to trap particulate material in the air. Home filters have ratings from one to twelve, with the higher ratings denoting better efficiency in removal of particles. The costs of a home HEPA filter, starts at $20 for use in a standard home air conditioning unit and this is much higher than for ordinary home air purifiers normally in use for such purposes. It is estimated that pollution in enclosed spaces like homes or offices is five times more than in outside air; thus air filtration for HVAC systems used for cooling or heating is very important. Most HEPA filters cannot be easily cleaned and using such filters may mean that they require replacement at regular intervals; thus increasing the cost of the HVAC application. They are also very fragile and can get damaged during installation. Most manufacturers of HVAC equipment suggest that HEPA filters be replaced at least twice a year if being used constantly.


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    • Distant Mind profile image

      Distant Mind 5 years ago

      Very informative.