ASSESSMENT OF MAN-MADE MINERAL FIBRE SIZE DISTRIBUTIONS BY SCANNING ELECTRON MICROSCOPY

The different methods used to assess the fibre size distribution of man-made mineral fibres are reviewed with special attention to the scanning electron microscope. In order to investigate to what extent the measurement of the fibre size distribution obtained from photomicrographs may differ from that obtained directly from the screen of a scanning electron microscope, comparative measurements have been made. It is shown that the use of a frame integration system associated with a slow scan speed gives acceptable results for non-superfine fibres when measurements are made on the screen of the cathode ray tube for aerosols characterized by standard size distributions. However, in order to obtain the best description of fibre number and size distributions of finer aerosols one must work from photomicrographs.