Workers engaged in automatic moulding mixtures preparation inhale aerosols with the particles' mass-median diameter 3.5 micromicrons, whereas the main parameters of the particle inhaled in steel bar rolling mills are 17.7 and 30.8 micromicrons respectively. The highest content of coarse dust fractions (up to 40 mg/m3) with the particles' diameter above 7 micromicrons, e.i. most affecting the bronchopulmonary system, was found in the cleaners working places. Workers of some other professions inhale dust complex particles with the diameter of 7 micromicrons, and polymodal aerosols with the maximum distribution among the particles within 4.3 and 11.7 micromicrons.