When most air filter professionals are asked to give information on what particles certain filter ratings/MERVs catch they refer to fractional efficiency curves or charts that show a particle size in microns on one axis and a removal percentage on the other axis. For years here at Filtration Systems we have said these standard fractional efficiency charts/graphs are misleading and do not offer any real or valuable information.
To provide more meaningful information we created graphs like the one above that combine the particle removal efficiency of different air filter ratings/MERVs and the amount of particles that are typically in ambient air. When you see the information in this way it actually helps explain what the benefit/value of MERV 8 vs MERV 11 vs MERV 13 truly is related to air quality. When evaluating the data in this way, it is clear that MERV-13 offers a significant advantage over lower MERV filters.
There are also several organizations that focus on indoor air quality, sustainability, and quality of life issues that also encourage the use of MERV-13 as a minimum standard:
- GSA Facility Standards
- Minnesota State Facility Design Standards
- Wisconsin Department of Public Instruction
- Environmental Protection Agency Office of Research and Development
- United States Green Building Council LEED Standards
- The WELL Building Standard
Unfortunately the HVAC air filter industry in the United States seems to want to keep the status quo and keep using the outdated and misleading air filter fractional efficiency curves and charts of the past. This is made clear in the opposition to the new global ISO 16890 standard for rating air filters that has been adopted everywhere else in the world.
The biggest change ISO 16890 introduces that makes it so much more user-focused than the filter manufacturer-focused MERV system, is that it produces a rating that clearly tells people what the filter removes i.e. 75% of ePM2.5 particles. It also eliminates the false efficiencies currently allowed by ASHRAE 52.2 standard.
The good news for air filter purchasers, facility management technicians, and indoor air quality professionals is there is support from ASHRAE to use ISO 16890 because the terminology used in other current ASHRAE standards uses PM as the basis. By accepting ISO 16890 it would make it easier to write standards and specifications because there wouldn't need to be a conversion between an IAQ goal for PM and the goofy and arbitrary MERV system of 52.2.