ISO 21501-4: Determination of Particle Size Distribution – Single Particle Light Interaction Methods – Part 4: Light Scattering Airborne Particle Counter for Clean Spaces

Overview and Purpose

ISO 21501-4 specifies the calibration and verification methods for light scattering airborne particle counters (APCs) used in clean spaces. These devices are crucial for measuring the size distribution of airborne particles based on their light scattering properties. The standard is essential for ensuring the accuracy and reliability of particle counters in environments where air purity is critical, such as semiconductor manufacturing, pharmaceutical production, and surgical rooms.

How the Test is Conducted

1. Calibration: The standard outlines the procedure for calibrating APCs, including the selection of calibration particles, the calibration process, and the verification of the calibration. Calibration ensures that the particle counter accurately measures particle sizes and concentrations.
2. Verification: After calibration, the performance of the APC is verified to ensure it meets the specifications outlined in ISO 21501-4. This includes verifying the size resolution, counting efficiency, and false count rate.
3. Environmental Conditions: The standard also specifies the environmental conditions under which the calibration and verification should be performed, including temperature, pressure, and humidity, to ensure consistency and accuracy.

Purpose of the Standard

• Accuracy in Clean Spaces: Ensures that APCs used in clean spaces accurately measure particle size distribution, which is critical for maintaining the required cleanliness levels.
• Quality Control: Provides a basis for quality control in environments where air purity directly impacts the production process and product quality.
• Compliance and Standardization: Helps manufacturers and users of APCs comply with international standards, facilitating global trade and interoperability of measurement devices.