For sampling A-dust the following sampling systems are available at the GSA:
- SG10-2 with FSP-10 (personal sampling)
- PM4-2 with fine dust head (stationary sampling)
- VC25-2 with fine dust head (stationary sampling)
Prior to the determination of crystalline silica (quartz & cristobalite) in the alveolar dust fraction, the mass of A-dust on the filter medium to be analysed must be determined.
We recommend to choose a measuring duration so that a volume of 2 m³ is reached in order to be able to detect 1/10 of the limit value (0.05 mg/m³).
- FTIR-spectrometer Spectrum TWO and Spectrum 100 by Perkin Elmer
Preparation of sampling
The collected cellulose nitrate filter is incinerated with the aid of a cold ashing device under oxygen supply. In the cold ashing device, at 60 °C, the filter substrate as well as interfering organic components of the dust sample are oxidised away. The resulting residue is then homogenised with potassium bromide and pressed into a compact.
An absorption spectrum in the range of 4000 cm-1 to 400 cm-1 is recorded from this compact with the aid of the FTIR spectrometer, which is then used for evaluation. The detection limit here is 10 µg or 20 µg absolute. We recommend to analyse a blank value.
Limit value and assessment standard
The Federal Ministry of Labour and Social Affairs announced an assessment criterion for quartz (A-dust) of 50 μg/m³ (0.05 mg/m³) on 27 July 2016. The assessment criterion must be taken into account in the risk assessment and for checking the effectiveness of the protective measures and must not be exceeded.