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5. Dust Control Measures for the Chrysotile Product Manufacturing Sectors


There are many locations in chrysotile-using factories where asbestos dust could be generated and released into the air. Controls are needed to prevent this from happening. The general principles of dust control apply to the manufacture of asbestos-cement pipes and sheets, friction products (such as car brake linings), sealants, gaskets, coatings, textiles and to the installation and repair of these products. The methods of dust control described below are straight forward, effective and are readily available. Experience has shown that using basic control measures and with sound housekeeping methods and work practices, modern chrysotile product factories can achieve exposure conditions well below 1.0 f/ml.

5.1  Control at the source
Control of dust should be achieved as near the source as possible. This increases the efficiency of the control process, minimizes costs and prevents the spread of dust into adjacent areas. The process of control must prevent emissions to the environment in order that a localized hazard in the factory is not converted into an environmental hazard. Therefore, if enclosure of the source is possible, this would be the first step to be taken.

There are very few viable alternatives to exhaust ventilation, except the use of water in specific instances. Generally, this consists of the application of a fine spray directed at the source of dust, such as a cutting tool or saw, drilling, material deposited on the floor, etc. The spray must be gentle or asbestos is likely to be distributed together with very small water droplets. Also, care must be taken to collect and properly dispose of the wetted material and/or water containing the material.

5.2  Engineering controls
Engineering controls can include the following equipment: dust hoods, ductwork, dust collector, and make up air. Proper engineering of each one of these components is essential. Among the different operations where industrial ventilation can be used are debagging, mixing, weighing, cutting, grinding, etc. A proper preventive maintenance schedule should be introduced to keep the equipment in good order.

The bag house, which filters the air must be sized to handle the quantity of air flow being exhausted. In modern practice the bag filter is the universally approved method of removing asbestos dust from air. The clean air passes then through the suction fan and is exhausted to the outside. Cotton is the most efficient filter fabric for asbestos dust collection. Proper maintenance of the bag house will ensure that no significant stack emissions enter the general environment.

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