[Occupational hygiene control of dust conditions in the working place using a 3-step dust measuring device].

Mineral dust originating at deep mining are polydisperse of a broad spectrum. The size of the largest particles is about 50 to 200 microns. At inspiration the particles undergo a selection according to their size: the particles exceeding 200 microns are not inhaled, particles exceeding a size of 15 to 20 microns remain in the tracheobronchial tract (NPL-fraction), granules smaller than 5 to 8 microns will be deposited in the alveolar region (A-fraction).-Selection of dust has been characterized by international conventions, i.e. the A-fraction by BMRC-characteristic. In the case of inert and fibrous mineral dust environment--from the five dust fractions--the A-fraction as the risk factor for pneumoconiosis and the TB-fraction as the risk factor for "dust bronchitis" may have an importance. Therefore concentration of these two fractions has to be systematically measured.--The paper presents a dust gravimeter--new in its structural composition--suitable for measuring concentration of the two fractions simultaneously and separately.