Dusts - Fibres

Microscopes in the lab

Stereo and phase-contrast microscope for identifying asbestos with coupled digital image capture
Source: IFA

In this section of the Chemical and Biological Hazards Department, two working groups analyse atmospheric and material samples for dusts and their mineral constituents and for fibres.


The focus of the work lies upon determining the concentration of respirable, inhalable and wood dusts by weighing. The following substances are detected individually in the dusts: quartz (by X-ray diffraction and Fourier transform infrared spectroscopy - FTIR), diesel-engine emissions (by coulometry), and amorphous silicic acids and talc (by FTIR). In addition, X-ray diffraction is used for the analysis of cristobalite, tridymite, silicon carbide and graphite. Sedimentation analyses and laser granulometry are used to determine the particle-size distributions and proportions of defined particle fractions of material samples and settled dusts. The qualitative composition of settled dusts is analysed by means of phase-contrast microscopy techniques and determined in combination with qualitative FTIR and X-ray diffraction analyses.


Measurement of the concentration of respirable fibres (WHO fibres: length > 5 µm, diameter < 3 µm, length-to-diameter ratio > 3:1) by means of scanning electron microscopy (SEM) and optical microscopy constitutes the main function of the working group. SEM EDX analyses are used to identify asbestos, mineral wool, aluminium silicate, aluminium oxide, silicon carbide and talc fibres, and to determine their concentrations. A catalogue of criteria has been developed for identification and differentiation of asbestos and other fibres in mineral raw materials and has now been incorporated into the body of technical regulations. Product fibre concentrations of a range of inorganic fibres are also determined. Material samples are analysed for asbestos and other types of fibre for the assessment of a potential asbestos hazard during redevelopment work.

In addition to this area of activity, methods have been developed in recent years for the quantification of toner particles in air (phase contrast microscopy) and for determining the concentration of carbon nanotubes (SEM EDXA).