scope:

This guideline describes the use of optical aerosol spectrometers to determine the particle number concentration and particle size distribution in ambient air and in test aerosols.

Optical aerosol spectrometers are suitable for the measurement of the total number concentration and for the continuous determination of the size distribution of aerosol particles. With instruments of this kind, it is possible to measure the light scattering equivalent diameters of airborne particles directly in situ.

Optical aerosol spectrometers are used in clean room technology, for measurements in ambient air and for measurements performed on test aerosols. Since the particle number concentrations in clean rooms can be more than six orders of magnitude lower than in ambient air, the instruments employed here have been especially developed for this application and are not suitable for measurements in ambient air. The measurable particle size range extends from about 0,07 μm to about 25 μm diameter. Number concentrations of less than 10^-3 cm^-3 (clean rooms) to a maximum of about 10⁵ cm^-3 can be measured. Since the aerosol flow rate (approx. 0,005 l/min to approx. 28 l/min) and the maximum permitted concentration can vary by orders of magnitude, the choice of the instrument depends on the specific measurement task.