When it comes to air filters, MERV 11 and MERV 13 are two of the most popular options. MERV 11 furnace filters have a particle retention rate of just over 90%, while MERV 13 air conditioning filters have a particle retention rate of around 98%. This makes the latter significantly more efficient. The main difference between the two is that MERV 13 filters are better at trapping fine particles.
They can capture 50% of particles that are 0.3 to 1.0 microns in size, compared to MERV 11 filters which can only capture 20%. This means that MERV 13 filters can trap bacteria, viruses, smoke, and microscopic allergens. The quality of an air filter is evaluated by its classification, which indicates its ability to block out particles in the air. The higher the rating (for MERV, FPR, and MPR), the smaller the air and dust particles your home air conditioner filter can capture.
For homes where allergies and asthma are a priority, choosing between a MERV 11 or a MERV 13 filter can block up to 98% of air contaminants and trap microscopic particles between 0.3 and 1.0 microns in size. In addition to filtering the usual dust, dust mites, lint, and pollen that trap other filters, MERV 13 filters can filter smoke, smog, microscopic allergens, viruses, bacteria, mold, exhaust fumes, and pet dander from several pets. However, if the MERV rating is too high (above MERV 1), it can increase system backpressure and block airflow through the central air conditioning system, worsening the effectiveness of the HVAC system. In most homes and commercial buildings, filters with a MERV rating between 8 and 13 will sufficiently filter the air.
According to the EPA, MERV 13 filters are 90% efficient when capturing particles between 3.0 and 10 microns, an efficiency of 85% when capturing particles between 1.0 and 3.0 microns, and an efficiency of 50% when capturing particles between 0.3 and 1.0 microns. Despite their many qualifications, high-efficiency filters are not needed in most homes. MERV 13 filters are suitable for homes in densely populated areas with high levels of air pollution, people who are immunosuppressed, and people with severe allergies and asthma. The particle size of the COVID-19 virus is 0.1 microns, a measurement that MERV 13 filters are unable to catch; however they do provide greater protection against airborne bacteria and viruses that spread through airborne droplets.
