OR-25-002 - ASHRAE Standard 52.2 Performance and Recommendations (RP-1784) ✓ Most Recent

This paper is based on findings resulting from ASHRAE Research Project RP-1784. Choosing an air filter by minimum efficiency reporting value (MERV) rating is almost 25 years old. MERV is one product of ASHRAE Standard 52.2, first published in 1999. This method is used to determine the particle size-dependent efficiency over a range of particle sizes and levels of dust loading. Over time, this method has been changed and updated. This paper discusses changes made to both Standard 52.2-2007 and 52.2-2012, how well they improved the data product, and what results can be expected when filters are tested in different laboratories. The results presented are the product of an interlaboratory study (ILS) on the method. This project tested five types of filters with advertised MERV ratings from 8 to 16. Based on these results, the expected MERVs for filters have a very small range for higher-efficiency filters, but they can vary across four levels for lower-efficiency filters. These lower-efficiency filters have more innate variation between filters, which influences the results. However, the shapes of the efficiency curves for all five MERV levels are reasonable, with no inexplicable oddities as were seen in quite a few of the curves in the 2005 ILS study done in 2005 before changes were made to either the 2007 or 2012 versions. In short, the method has definitely improved.

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