ISO 21501-1:2025

Determination of particle size distribution — Single particle light interaction methods — Part 1: Light scattering aerosol spectrometer ISO 21501-1:2025

Publication date:   Dec 10, 2025

Scope

This document specifies characteristics of a light scattering aerosol spectrometer (LSAS) which is used for measuring the size, number concentration and number-based size distribution of particles suspended in a gas. This document provide the calibration procedure and the validation method for aerosol spectrometers.
This document applies to:
—    characterization of metered dose inhalers (MDI), dry powder inhalers (DPI) and nebulizers in pharmacy;
—    production control of active agents;
—    cut-off determination: impactors, cyclones and impingers;
—    atmospheric aerosols: bio-aerosols, stables or composting facilities, nebulized droplets, measurements in street tunnels;
—    fractional separation efficiency determination of filters.