Description

The primary standard for particle counter calibration is ISO 21501-4. The calibration is executed by comparing the values of size and number of particles of polydisperse, mainly atmoshperic aerosol, measured by calibrated gauge, to the values of size and number of particles measured by counter, designated as standard.

This new standard, ISO 21501, incorporates a number of new tests that are designed to reduce count variability between different instruments. Specifically, the standard specifies new counting resolution and counting efficiency tests be performed at routine calibration cycles, typically every six or twelve months.