scope:

This Recommended Practice (RP) covers procedures for calibrating and characterizing the performance of optical particle counters (OPCs) that detect and measure the size of single particles in air and other gases. These procedures are intended for use by OPC manufacturers, specialized test houses, and OPC users who maintain calibration and testing facilities to determine the sizing and counting accuracy of these instruments.

BACKGROUND AND PURPOSE

This RP provides standardized test procedures to calibrate and characterize the performance of optical particle counters. OPCs are used to define airborne particle size distribution and concentrations in air and other non-hazardous gases. The data obtained from these instruments is used to verify cleanroom and clean device classification, to characterize air filter performance, to verify installed filter system integrity, and to characterize particle emissions from potential contamination sources. It is often necessary or desirable to use different OPCs operating at different locations or different OPCs at the same location at different times. OPCs of different design may not produce the same data from identical gas samples. Such discrepancies may occur even with similar OPCs if calibrated differently. For these reasons, a standardized calibration methodology should be established to minimize variability among different OPCs. The procedures in this RP are designed to permit calibration of an OPC to produce reliable data in normal use.

The procedures defined in the RP include:

• Calibration of inlet flow rate (section 6)

• Sizing calibration (section 7)

• Zero count (section 8)

• Counting efficiency (sections 9 and 10)

• Presentation of counting efficiency (section 11)

• Concentration (coincidence) limit (section 12)

• Resolution (section 13)