ISO 21501-4-2018 PDF

Full title and description

Determination of particle size distribution — Single particle light interaction methods — Part 4: Light scattering airborne particle counter for clean spaces. This ISO standard specifies calibration, verification and performance requirements for light‑scattering airborne particle counters (LSAPCs) used to measure number concentration and number‑based size distribution of airborne particles in clean spaces and controlled environments.

Abstract

ISO 21501-4:2018 defines methods to calibrate and verify single‑particle light‑scattering airborne particle counters. It covers instrument sizing accuracy, counting efficiency, resolution, false counts, maximum measurable concentrations, sampling flow and time errors, response rate, calibration interval and reporting of test results. Typical measurement size range addressed by the standard is approximately 0.1 µm to 10 µm. Instruments meeting this standard are intended for use in the classification and monitoring of cleanrooms and associated controlled environments (for example under ISO 14644 series requirements).

General information

• Status: Published (Edition 2) — confirmed in 2023; amended by ISO 21501-4:2018/Amd 1:2023.
• Publication date: 18 May 2018 (Edition 2); Amendment 1 published February 2023.
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 19.120 (Particle size analysis / granulometry).
• Edition / version: Edition 2 (2018); accompanied by Amendment 1 (2023).
• Number of pages: 25 (ISO published document).

Scope

Specifies a calibration and verification procedure for light scattering airborne particle counters (LSAPCs) that perform single‑particle measurements in air. The standard applies to instruments intended to determine particle number concentration and number‑based size distribution in clean spaces and other environments where particle monitoring is required. It defines performance characteristics to be tested, limits or criteria for many parameters, and requirements for reporting test and calibration results.

Key topics and requirements

• Size setting (sizing) error and sizing calibration (typical range ~0.1 µm to 10 µm).
• Counting efficiency (including first channel efficiency and downstream channels).
• Size resolution and instrument resolution limits.
• False count (zero count) tests and limits.
• Maximum particle number concentration and linearity/performance at high counts.
• Sampling flow rate accuracy and volumetric flow requirements.
• Sampling time and sampling volume error limits.
• Response rate and temporal performance for transient conditions.
• Calibration interval recommendations and traceable calibration practice.
• Required content and format for test and calibration reports.

Typical use and users

Used by cleanroom operators and facility managers, pharmaceutical and biotech manufacturers, semiconductor and microelectronics producers, medical device manufacturers, calibration and test laboratories, instrument manufacturers and quality/compliance personnel who require traceable, repeatable airborne particle measurements for classification, monitoring and process control in controlled environments.

Related standards

ISO 21501-4 is part of the ISO 21501 series of single‑particle light interaction methods (other parts address aerosol spectrometers and liquid‑borne counters). It is commonly used alongside ISO 14644‑1 and ISO 14644‑2 (cleanroom classification and monitoring) and related metrology/calibration standards and guidance used by calibration laboratories and instrument manufacturers.

Keywords

airborne particle counter, light scattering, LSAPC, particle sizing, counting efficiency, cleanroom, calibration, verification, particle number concentration, ISO 21501

FAQ

Q: What is this standard?

A: ISO 21501-4:2018 is an international standard that specifies calibration, verification and performance requirements for light‑scattering airborne particle counters used in clean spaces.

Q: What does it cover?

A: It covers sizing accuracy, counting efficiency, resolution, false counts, maximum concentration limits, sampling flow/time accuracy, response rate, calibration intervals and the format/content of test/calibration reports for LSAPCs measuring roughly 0.1 µm to 10 µm.

Q: Who typically uses it?

A: Cleanroom operators, pharmaceutical/biotech and semiconductor manufacturers, medical device producers, calibration laboratories, test houses and particle counter manufacturers use this standard to ensure instruments meet required performance for monitoring and classification tasks.

Q: Is it current or superseded?

A: The current issued edition is ISO 21501-4:2018 (Edition 2). This edition was confirmed and remains current with an accompanying Amendment 1 published in 2023.

Q: Is it part of a series?

A: Yes. ISO 21501-4 is one part of the ISO 21501 series (single particle light interaction methods), which includes other parts addressing aerosol spectrometers and liquid‑borne particle counters.

Q: What are the key keywords?

A: Keywords include airborne particle counter, light scattering, calibration, counting efficiency, particle sizing, cleanroom monitoring, LSAPC, ISO 21501, particle number concentration.