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9. Working with chrysotile-containing friction materials


9.1  Brake repair and installation
Asbestos fibre may be found in the dust deposited on brake assemblies and as a result, measurable concentrations of asbestos fibre exist in the work environment of workers engaged in repair operations. Therefore, precautions must be taken to prevent exposure of the worker to asbestos fibre that may occur during automotive brake repair and installation. In the past, the wheel and brake assembly was cleaned by using a compressed air hose and/or various types of brushes. Needless to say, this operation generates dust which is released into the workplace atmosphere. Because of the risk to workers, use of compressed air is prohibited and should never be condoned. It is important to note that many of the non-asbestos fibres used in friction materials are believed to be hazardous to human health and must be handled with caution. In fact, a major friction material manufacturer has recently alerted all its clients to the need to apply the same control measures for work with all types of friction materials, whether they contain chrysotile or other fibres.

Several alternative methods exist. One consists of spraying the wheel/brake assembly with a fine mist of water to thoroughly soak the dust. This is followed by a stronger jet of water to wash the wetted dust off the assembly. A sufficiently large container is positioned underneath the assembly to collect the contaminated water. This water can be discarded into the sewage system.

A second method consists of a compressed air hose fitted at the end with a bottle of solvent that can be sprayed onto the brake assembly to loosen the deposited dust and to capture the resulting airborne dust in the solvent mist. The worker should begin spraying the parts that may be contaminated by asbestos with the solvent from a sufficient distance to ensure that the dust is not dislodged by the velocity of the solvent spray. After the dust is thoroughly wetted, the spray may be brought closer to the parts to remove grease and other materials. The parts sprayed by the solvent mist are then wiped clean with a rag that must be disposed of appropriately. Rags should be placed in a labelled plastic bag or other container while they are still wet. This assures that the asbestos dust will not become airborne again after the brake and clutch parts have been cleaned. If clean-up rags are being laundered rather than disposed of, they must be washed using methods appropriate for the laundering of asbestos-contaminated materials.

The last, and most expensive, method uses the Enclosed Cylinder/HEPA Vacuum System. This enclosed unit is fitted with compressed air hose and a pair of rubber gloves that permit the worker to reach inside the cylinder. At the rear of the unit, a triple pleated fabric forms a seal around the axle behind the wheel. The apparatus effectively isolates dust from the worker's breathing zone and filters the air from the enclosed area through a HEPA vacuum cleaner.

If these work practices are applied, workplace exposures levels well below 0.1 f/ml can be achieved.

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