ISO 21501-1:20 09规定了光散射气溶胶光谱仪（LSAS）的特性，其用于测量悬浮在气体中的颗粒的尺寸、数量浓度和数量/尺寸分布。本文所述的光散射技术基于单粒子测量。通过该方法测量的颗粒的尺寸范围在直径约0.06 μ m至45 μ m之间。 符合ISO 21501-1:20 09的仪器用于在高达1011个颗粒/m3的相对高浓度下测定粒度分布和颗粒数浓度。 应用领域包括:药剂学中计量吸入器（MDI）、干粉吸入器（DPI）和雾化器的表征；活性剂的生产控制；切-关闭测定:冲击器、旋风分离器和冲击器；大气气溶胶:生物气溶胶、马厩/堆肥设施、雾化液滴、街道隧道测量；过滤器分数分离效率的测定。 对于上述应用，气溶胶光谱仪应尽可能精确地确定颗粒尺寸分布、颗粒数浓度、尺寸分辨率和尺寸精度。这些气溶胶光谱仪不适用于洁净室的分类。

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. The light scattering technique described in this document is based upon single particle measurements. The size range of particles measured by this method is between approximately 0,06 μm to 45 μm in diameter. Instruments that conform to ISO 21501-1:2009 are used for the determination of the particle size distribution and particle number concentration at relatively high concentrations of up to 10¹¹ particles/m³. Application fields include: 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/composting facilities, nebulized droplets, measurements in street tunnels; fractional separation efficiency determination of filters. For the above-mentioned applications, aerosol spectrometers should determine the particle size distribution, particle number concentration, size resolution and sizing accuracy as accurately as possible. These aerosol spectrometers are not suitable for the classification of clean rooms.