Research and testing were conducted to provide scientifically sound and technically-based specifications for particle counters in the ASHRAE 52.2 standard (ASHRAE 1287-RP). The question addressed goes to the heart of the standard - the particle counter. The standard is written around the use of optical particle counters (OPCs) to perform aerosol concentration measurements upstream and downstream of the test air cleaner.

While specifications for the particle counter are provided in the standard, there have been concerns that these specifications may not be adequate to ensure reproducible measurements from counter to counter. By developing improved specifications for the particle counters, it is anticipated that the accuracy and reproducibility of the 52.2 tests will be improved.

The project was conducted in two parts. Part I was a non-testing phase focused on identifying instances where differences in filter efficiency test results were believed to be OPC-related. Part II focused on testing and investigation to determine what aspects of the OPC were responsible for the differences and on defining new specifications for the particle counter that will eliminate or minimize such discrepancies.