MERV classification 13-16 filters are capable of trapping 90% or more of particles in the range of 1.0-10.0 microns. The MERV 13 will prevent less than 75% of particles of 0, 3-1 and 0 microns from passing through, the MERV 14 will reach 84%, the MERV 15 up to 94%, and the MERV 16 can trap 95% or more of the smaller particles. The Minimum Efficiency Report Value (MERV) rating for an air filter measures how effectively the filter prevents dust and other contaminants from passing through the filter and reaching the air stream. ASHRAE recommends a MERV 6 or higher, while the U.
S. Department of Energy recommends MERV 13 and LEED recommends MERV 8 as a minimum. Filters with higher MERV values trap small particles more effectively than filters with lower MERV scores. However, not all filters have a MERV rating, and many are purchased in large stores. Increasing a filter to a higher MERV can increase the delta P through the filter.
In addition, high-MERV air filters that contain pleats create much more surface area for air to blow through, which can improve airflow and reduce stress on the system. It is possible to use a high-MERV filter medium, clean it with compressed air and then insert the filter into a pocket of a homemade mask, between two layers of cloth. The Merv 16 would be the best option since it will filter 95%.Researchers have discovered that, while filters with a high MERV content can cause a certain drop in pressure, the impact is not significant unless the filter is laden with dirt. Vacuum bags are not safe for masks since they contain fiberglass, which is very bad for breathing (and worse when the bags have been cut to make inserts).
However, MERV air filters are made of polyester and cotton, so they should be safe. Using an air filter with a MERV rating higher than recommended by the boiler or air conditioner manufacturer may affect its performance. It is important to replace dirty filters frequently enough (&), that is, one or two weeks, depending on the MERV classification, the effective area of the filter and how many particles enter your home. A MERV 8 carbon filter will filter more than enough dust and allergens and filter dozens of toxic gases that will pass directly through the MERV 13 filter. And MERV 13 air filters block more than 99% of virus-carrying bacteria and airborne particles, so that indoor air quality and the environment are kept clean from all normal contaminants and allergens.