Document JrDnb21RXKJGd8NR2eGRgQR56

V I INTRODUCTION This study was undertaken to assess the degree of exposure to fibrous dust ain brake maintenance procedures on commercial vehicles and to provide comparative data relating to a previous study on operators working on passenger cars. II INVESTIGATION Air sampling took plaoe in the garage on the 19th September 1968. Membrane filters, in conjunction with Casella personal samplers, suitably modified to provide a flow rate of 200 were used and the following sampling procedure adopted. (a) Personal samples were collected from the "brake blow off" operator (Mr Crone) and the mechanic working in the adjacent bay (Mr Hillman) during the blowing-off operation. The filters were then ohanged and replaced to run for the rest of the shift. (b) Static samplers were positioned at three points, A, B and C, about 20-25* from the source of dust generation and separate samples were collected for the morning and afternoon shifts. The sampling positions are shown in Fig.l, The collected samples were subsequently removed to the laboratory and, after preparation, examined by projection microscopy for the presence of fibres greater than 5ju. (A fibre is defined as having an aspect ratio equal to, or greater than, 3:1). ... Ill RESULTS 8006 1214 HFM- 005800