MEASUREMENTS OF FIBER CONCENTRATIONS DURI NG HANDLING OF CERAMIC FIBER MATERIAL - COMPARISON OF FIBER DUST EVALUATIONS ACCORDING TO THE GERMAN GUIDELINES ZH-1 120.46 AND ZH-1/120.31/

Within a framework of a project supported by the Federal Ministry of R esearch and Technology (BMFT) over 100 fibre dust samples were taken a t industrial workplaces. The fibre dust samplings and the evaluations were carried out according to the guidelines ZH 1/120.46 (Scanning Ele ctron Microscopy) and ZH 1/120.31 (Phase Contrast Optical Microscopy). The investigations to the reproducibility of the scanning electron mi croscopy method indicated, that under optimum conditions the standard error for a single value amounts to approximately 20%. Special evaluat ions, which differed from the norm of the guidelines did not show any significant deviations. The comparison of both methods (personal air-s ampling, ceramic fibre material) verifies, that the scanning microscop y method provides significant higher fibre concentrations compared to the phase contrast microscopy method. With the aim of regression analy sis of the measured dust fibre deposite densities, equations were deve loped, which allow an estimation of the expected value and its confide nce interval of a method according to the evaluation of the other meth od. This estimation is only of use for fibre dust deposit densities hi gher than 350 F/mm(2).