HEPA filters are the top of the line when it comes to air filtration, with a rating equivalent to a MERV 17 or higher. These filters are designed to capture 99.97% of particles that are 0.3 microns in size, and even more of particles that are larger or smaller than that size. To test the efficiency of HEPA filters, they are tested with DOP, mineral oil, and other materials that generate monodisperse particles. The purpose of the MERV standard is to allow for comparison between different air filters. Given the threat posed by COVID-19 and other germs, replacing a building's air filter with a HEPA one is a much more effective measure than using a MERV 13 filter.
This is because the virus is very small, ranging from 0.06 to 0.12 microns in size. The higher the efficiency of the filter, the better it will be at trapping these particles. The Minimum Efficiency Reporting Value (MERV) rating for an air filter measures how effectively it prevents dust and other contaminants from passing through it and into the air stream. ASHRAE or MERV air filters are tested by testing for dust spots, which incorporate fine dust, powdered charcoal, and some cotton fragments. The MERV classification of an air filter describes its efficiency in reducing particles that are 0.3 to 10 microns.
High-efficiency particulate air (HEPA)
filters are far superior to MERV 13 filters and can be used in many HVAC systems.However, if the system is not designed to support this type of filter, using one can actually reduce air flow due to the finer filter material and cause more harm than good. In general, filters with a MERV 16 rating or lower are considered suitable for residential, commercial, and general hospital use. Although the classification does not exceed MERV 16, HEPA filters trap even smaller particles at a speed higher than that of MERV 16 and are generally used in surgical operating rooms, clean rooms, and other contexts that require absolute cleaning. MERV ratings range from 1 to 16, and filters with a higher MERV rating trap small particles more effectively than those with a lower rating. Additionally, FPR ratings only consider the filter's ability to capture or remove particles from 0.3 to 1 micron.
