Convert Swiss francs (CHF) to your currency. This document describes a calibration and verification method for a light scattering airborne particle counter (LSAPC), which is used to measure the size distribution and particle number concentration of particles suspended in air.

The ISO 21501-4 is the recognized standard for optical particle counter calibration. The International Organization for Standardization (ISO) introduced ISO 21501 in 2007 with the following purpose:

This first edition of ISO 21501-4, together with ISO 21501-2 and ISO 21501-3, cancels and replaces ISO 13323-1:2000, which has been technically revised. ISO 21501 consists of the following parts, under the general title Determination of particle size distribution — Single particle light interaction methods:

A list of all parts in the ISO 21501 series can be found on the ISO website. Any feedback or questions on this document should be directed to the user’s national standards body. A

iso 21501 For determination of particle size distribution for single-particle light-interaction methods This standard focuses primarily on calibration/verification methods used to ensure particle counters size and count particles accurately, using a traceable reference instrument.

ISO 21501-4 covers instrument calibration procedures to ensure air particle counter sampling measurement inaccuracies are reduced. A Counting Efficiency Test is also included as a final confirmation of air particle counting performance.

Particle counters are useful instruments for monitoring particle contamination in air. The purpose of this document is to provide a calibration procedure and verification method for particle counters, so as to minimize the inaccuracy in the measurement result by a counter, as well as the differences in the results measured by different instruments.

ISO 21501-4 clearly defines a recommended method of calibrating particle size, along with minimum requirements for differentiation between measured particles and noise. Figure 1 shows a pulse height distribution from a particle counter suffering from high noise levels.

ISO 21501-1:2009 specifies characteristics of a light scattering aerosol spectrometer (LSAS) which is used for measuring the size, number concentration and number/size distribution of particles suspended in a gas.