Guides & Toolkits

SILICA IN THE WORKPLACE 9 365-AXJ-01-iGDO © 2020, Workplace Safety & Prevention Services (WSPS) 1 877 494 WSPS (9777) | 905 614 1400 | wsps.ca WSPS.CA Ensuring that the specifications are met at the time of start-up is essential to future performance and maintenance. 3. Modification of Existing Equipment or Processes Control of silica in the workplace can sometimes be achieved by modifying existing processes or equipment. Less hazardous materials can sometimes be substituted for silica. Some examples are use of metal shot and grit to replace silica sand in abrasive blasting, and use of magnetite or aluminum oxide bricks in place of silica bricks in furnaces. This change should be examined carefully to ensure that product quality remains high and that other problems are not introduced. Use of silica may possibly be eliminated from the process when alternate technologies become available. Once again, the alternative should be examined to ensure that it meets the need at hand and does not introduce new hazards. The most common modification of existing processes is isolation. Sources of silica dust can sometimes be isolated from workplace air by enclosing the equipment or by separating it from workers by barriers or walls. Sometimes special booths may be used to isolate the worker from the source of silica dust. 4. Ventilation Ventilation of the workplace is essential to maintaining acceptable conditions of exposure. Workplace ventilation may be provided in two ways: natural or mechanical ventilation. Natural ventilation relies on the principle that heated air expands and rises. Natural airflow in a building can be obtained by providing openings at floor level and roof level. This type of ventilation is most effective when the openings are as far apart vertically as possible and the inlet and outlet areas are equal. Mechanical ventilation is provided by fans. This may be required when natural ventilation is inadequate. Exhaust fans located at roof level may supplement natural ventilation in controlling dust generated by process emissions. More effective mechanical ventilation is provided by local exhaust systems. The collecting hood should be located as close as possible to the source of emission. The air velocity measured at the opening of the hood, the capture velocity, must be sufficient to collect the dust. Generally the face velocity must be at least 60 m/min (220 ft/min). The ACGIH Industrial Ventilation, a Manual of recommended practice for design, 26th edition, 2007 lists a range of capture velocities depending on the condition of dispersion of the contaminant into the air. Ventilation and dust control systems need to be designed by a trained professional in compliance with applicable legislative requirements.

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