Document pp9JM441DNyRJ84k4gbOyYk87

ix> > Removing daUi (ram brake wumbhri during vehicle servicing 3) ' A fi*"* sampling period or some 5 min was chosen for the determination of mast concentration*--(his being longer than required for the blowing operation but sufficient to cover that required for the alternative denning methods. The dust col lected by the static sampler dote to the brake assembly gave an equivalent concen tration of 114 mg/m and that for the personal air sampler 42 mg/m*. It is probable that many of the particles induded were larger than respirable size. The few asbestos fibres counted on membrane filter samples gave a concentration of the order 3-5 fibres/cm*. ALTERNATIVE CLEANING METHODS Initial approaches were to try the use of fixed and hand-hdd extractors to collect the dust panicles removed by hand-brushing with a small paint brush. Fixed ex tractors, although reasonably efficient, were rejected because of restrictions which these placed upon the work by confining it to one area. Both operatives and super vision were unhappy about being confined to one work area--preferring to retain flexibility and carry out the work as they had previously done, wherever the vehicle happened to be. Portable extraction equipment was dearly required and after some preliminary' enquiries, a BVC industrial vacuum' cleaner was selected for use in experimental work. It is of fairly conventional type, powered by a | h.p. motor and supplied with disposable paper bags in addition to the normal doth bag. The psper bags are fitted in a manner which allows them to be scaled fairly easily before removal. To trap any particulates which might pass through the paper and cloth bags, an ex ternal, multi-layer filter was provided Tor fitting to the air outlet end of the cleaner.Preliminary experiments established that some brake dust panicles were passing the paper and doth bags but these were trapped by the externally fined filter. Sampling at the exit ride of the filter established that no panicles passed the filler. V . CONDITIONS OBTAINED USING THE VACUUM CLEANER AS A SOURCE OF EXTRACTION The first technique tried was to use the nozzle of the deaner, hand-hdd as a source of local extraction whilst the dust deposits were disturbed with a small paint brush held in the other hand. The Tyndall Beam showed that some dust was escaping into the environment. Objective measurements arc summarized in Table 2. Tabu 2. Rnuus or KoMuem samtus bvmmo musinNo and WITH LOCAL EXT*ACTION Sample Number of brake dust partic)es/5em* Taken at nan of process Taken about 1 min later Taken about 2 min later Taken at end of process 1070 404 426 446