Model 11-R
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Additional analyses are possible using the Windows 1178 software. These are:
For occupational medicine, the three dust mass fractions according to EN 481, inhalable, tho-
racic and respirable in µg/m³
Immissions, the three dust mass fractions PM10, PM2.5 and PM1 in µg/m³
Measurements that can be determined:
- Particle counts in 31 count channels, in particles per litre
- Particle mass in 31 mass channels in µg/m³
4.4 Mode switching particle count/particle mass
On the Mini-LAS 11-R: See 3.5.1.2 “Setting the measuring mode and selecting the size channels to be
displayed”
Via terminal software: “N” to switch to normal mode (mass)
“C” to switch to count mode
4.5 Gravimetric control of the dust mass and Determining the gravimetry fac-
tor (C-factor)
Due to the fact that the measuring device does not determine the dust mass directly but indirectly by
means of optical scattered light measurement, the results have to be corrected for the respective meas-
uring location with a gravimetry factor known as the C-factor. The C-factor can be determined with the
gravimetry filter installed in the device.
The C-factor depends on the particle density, form and refraction index of the particles.
Therefore it has to be determined for each type of dust.
This is essential for workplace measurements in particular, since very different types of
dust are often found here.
If the C-factor is not known, measuring is performed with the value 1 and the gravimetry is carried out
after the measurement.
Gravimetry requires a micro-scale with a high resolution and precision. For a given reso-
lution of 10 µg, a total mass of approximately 1 mg should be present on the filter so that
the weighing error is kept small enough to be disregarded. The required collection period
is determined from the existing dust concentration and the sample volume flow.
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