The Standard 52.1-1992 is the old US - standard for performance testing of HVAC air filters. This standard is however still sometimes quoted and provides three evaluation criteria:

  • dust spot efficiency
  • arrestance
  • dust holding capacity


The 52.1 standard is "replaced" by standard 52.2-1999, that provides more realistic data on filter performance. It provides filter’s initial efficiency as a function of particle size, as well as a numeric value that allows a user or engineer to specify a product's minimum efficiency reporting value (MERV).

To understand the differences between the EN:779, EN:1822 and ASHREA 52.1 and 52.2, see our comparison chart below.

EN vs ASHRAE comparison (pdf)

Or read the Camfil Farr overview, which fully explains the ASHREA standards and how to use them.

ASHRAE Testing for HVAC Air Filtration


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