A recently by the National Institute for Occupational Safety and Health
published handbook was developed to identify available engineering controls
that can assist underground and surface metal/nonmetal mining operations in
reducing worker exposure to respirable silica dust. The controls discussed in
this handbook range from long-used controls which have developed into industry
standards, to newer controls, which are still being optimized.

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AplusA-online.de - Source: National Institute for Occupational Safety and Health