When it comes to air filtration, HEPA filters are the gold standard. However, there are different grades of HEPA filters, ranging from H10 to H14. The higher the grade, the higher the performance. Filters H10 to H12 are sometimes referred to as True HEPA filters, while H13-H14 HEPA filters are within the highest level of HEPA air filtration and are considered medical grade. In accordance with the EN 779 standardization standard, there are different classes of HEPA filters.
Classic HEPA filters are usually class H10, H11 or H12. The best HEPA air purifiers will use H12 HEPA filters. According to the Institute of Environmental Science and Technology (EST), there are 6 types of performance: A, B, C, D, E & F. Each has its own distinctive characteristics, as shown in table 1 below. HEPA filters come in many forms with differentiating factors, such as grade, class or MERV rating.
There are standards set by the Department of Energy (DOE), but the type of HEPA filter may vary by manufacturer. For example, the Levoit LV-H135 comes with a medical-grade HEPA filter that can capture more than 99% of the smallest air pollutants that are small, up to 0.1 microns in size. Specifically, the H13 filter captures particles that are more than 3 times smaller than classic HEPA filters. That's why modern air purifiers come with a detector that tells you when HEPA filters need to be changed.
When looking for air purifiers and air filters, it's important to note that HEPA filters are available with different levels of efficiency. According to Department of Energy standards, a HEPA filter must remove at least 99.97% of particles in the air that have a diameter of 0.3 microns, also known as microns. A HEPA H13 filter can trap 99.95% of particles of 0.1 micron in diameter, while a HEPA H14 filter can capture 99.995%. The uneven weave of the filter screen results in a large amount of air swirls and small particles are adsorbed to HEPA under the action of the air cyclone.
All in all, you can see that improved HEPA H13 air purifiers are more difficult to incorporate into an air purifier. The highest MERV grade support is MERV 13-16, but HEPA filters are generally classified as MERV 17 because of their ability to capture particles as small as 0.3 microns or up to 0.1 microns for medical grade HEPA filters. HEPA filters began as a defense against nuclear particles but have since been commercialized for everyday consumers to use in a more diverse way. Today, they're used in HVAC (air purifiers, air conditioners), biochemical applications and overhead lines. Although they're often the greatest defense against particles in the air, when combined with additional filtration or sterilization they can further improve air quality and extend the life of the filter. In theory, a HEPA filter is any filter that can capture at least 99.97% of very small particles of 0.3 microns in size.
In HEPA H13 filters, True HEPA filters mainly target particles of 0.3 microns while HEPA H13 filters target particles even smaller than 0.1 microns.