2.1 Particle measurement with Grimm's Dual-Technology
The dust aerosol spectrometer and dust monitors model 1.108 and 1.109 are compact portable devices
which have been built for continuous measurement of airborne particles as well as for measuring the
particle count distribution. They possess an integrated gravimetric filter on which all particles are collected
after the optical measurement and thus are available for further analysis. This “Dual-Technology“ is unique
and patent-registered by Grimm Aerosol Technik.
The data can be displayed as particle concentration in the unit particle/liter and also as mass
concentration in the unit µg/m3
. By means of the Grimm Windows Software additionally different dust
mass fractions can be displayed as well as the calculated particle surface area. The standardized dust
mass fraction is in terms of occupational health respirable, thoracic and alveolic according to EN 481. A
second dust mass fraction is named immission PM10, PM2.5 and PM1. These are provided for
comparisons of indoor and outdoor measurements, but are not in compliance with US EPA or European
approval for equivalent measurements EN 12341. The measuring principle of the model 1.108 and 1.109
is the light scattering of single particles with a semiconductor laser as light source. Inside the measuring
cell the scattering light is being led directly and via a mirror with a wide opening angle onto the detector
(see figure 1 and 2). The detector is positioned in the right angle to the incident laser beam. This setup of
the detector is denominated as 90° scattering light detection. This optical alignment increases the
scattering light collected by the detector and optimizes the signal-to-noise ratio. Therefore even very small
particles down to 0.25 µm respectively 0.3 µm can be detected. The optical setup moreover abrades the
MIE scattering undulations caused by monochromatic illumination as it is typical for laser light scattering
spectrometers and therefore enables a definite particle sizing. If a particle crosses the laser beam, it
creates a light pulse. The signal of the detector diode will be classified into different size channels after
accordant amplification. Model 1.108 possesses 15 size channels, whereas the model 1.109 is in
possession of 31 size channels. This way the particle size distribution can be measured which provides
the basis for the calculation of the dust mass. That is why these devices are suitable for a variety of
applications like for instance the compilation of occupational health data, dust analysis, inhalation
toxicology, aerosol research, or atmospheric research.