The aim of the work was to check, in the selected ceramic plants, whether the replacement of asbestos heat-insulating material by mixed material or fibrous material free from asbestos decreased the risk of exposure to mineral fibre dust among workers engaged in the overhaul of furnace trucks and ceramic furnaces. In the 6 selected plants which used various heat-insulating materials, dust concentration was measured (personal dosimetry), composition of mineral dust, collected from air at overhaul posts, was identified (RTG and IR methods), and morphology of dust particles was examined (optic microscopy and TEM). The highest concentration of respirable mineral fibres was found during the overhaul of a truck with asbestos insulation; respirable fibre concentration reached the value of 5 f/cm3, and total dust concentration-the value of about 80 mg/m3. Insulating plates made of asbestos paper-board proved to be the major source of the mineral fibre emission; mean weighted dust concentration in the plants under study ranged from 2.0 to 2.7 f/cm3. The replacement of asbestos plates by plates made of other heat-insulating materials have lowered respirable mineral fibre dust concentration by ten times. In dust samples collected from the air at the overhaul workposts, the presence of chrysotile, forsterite, quartz and cristobalite (asbestos heat-insulating materials) as well as cristobalite and mullite (non-asbestos heat-insulating materials) was found.