HEPA, or high-efficiency particulate air, is the ultimate standard for air filtration. These filters are renowned for their ability to filter out microscopic substances such as mold, dust and pet dander, with an efficiency rate of at least 99.97% for particles as small as 0.3 microns. While it is rare and generally not recommended to use a HEPA air filter in a traditional home HVAC system, there are some homes that have been built to accommodate them. However, the cost and size of HEPA filters would be exorbitant, and the entire air conditioning system would have to be redesigned for the ducts of the typical home air conditioning system, and the air controller could not handle the increased airflow resistance of a HEPA filter. The good news is that if you want a highly effective filter for your home, the EPA (United States Environmental Protection Agency) reports that air conditioning filters with a MERV rating of 7 to 13 have a “chance of being almost as effective as true HEPA filters”.
ULPA filters can, in theory, remove a higher percentage of contaminants, but they require powerful airflow and a fast air exchange rate. There are also HEPA filters that are used in water purification systems; however, in these applications the term HEPA air filter is debatable, since filters are used to remove contaminants found in water rather than air. With all the false advertising that exists, many people may think that they have or may have a HEPA filter in their home. To be considered a true HEPA filter, it must be able to capture up to 99.7 percent of all contaminants 0.3 microns or greater using a dense mesh of fibers arranged in a specific configuration. Remember that the air in your home is recirculated, so the same air will pass through the filter several times a day.
This is how the fibers of a glass fiber mesh of a HEPA filter could actually be spaced between 0.5 and 2.0 microns wide, but still successfully filter a contaminant 0.5 µm wide and have a 99.97% chance of doing so. Whole home air filtration units worth considering are Airwash Whisper 350, Airwash Whisper 675, Amaircare 3000, Amaircare 7500 for residential homes or Amaircare 10000, etc. for air purification in industrial spaces. CNN suggests in its antiviral article: “Look for a model with a HEPA filter, which is what most allergists and doctors recommend. Segments that need more filtration would mean greater static and, which would mean greater airflow with larger diameter fans, and all of this would eventually increase the total cost of capital expenditures and operating expenses on the project, so you should carefully choose the right filter for your applications. This does not mean that the smallest particles are ignored by the filter; many are trapped but not at the 99.97% level (about 0.2 or less can be trapped at the 99.95% level). While we wait to see if the world will adopt a universal classification standard (known as ISO 2946), just know that if a filter is marketed that can remove at least 99.97% of contaminants 0.3 µm in size or larger, it is a true HEPA filter. HEPA filters don't undergo any real MERV tests but receive a MERV rating to “put them on the map”.
In the US, it is widely accepted that a True HEPA filter needs to be able to filter 99.97% of particles of 0.3 µm or greater; however, they are rarely used in residential applications due to their cost and size. Supermarket and Large Space HEPA Filters Market HEPA filters are high-efficiency filters designed for use in critical applications such as pharmaceuticals and industries but with very limited use in supermarkets.