Monthly Round Up of Important Ideas and Standards in
Industrial Hygiene and Safety
IN THIS ISSUE: Tool-mounted Shrouds
Tool-mounted shrouds attached to local exhaust ventilation can reduce the amount of dust in the air generated during sanding, grinding, and cutting. Tool-mounted shrouds follow two basic principles of ventilation and industrial hygiene:
- The closer the suction is to the source, the more effective it is.
- The closer the suction is to the source, the less exhaust air is needed.
Tool-mounted shrouds consist of two parts:
- A tool such as a grinder, saw, or sander fitted with a shroud that completely encloses the spaces around the exhaust entry point.
- A portable dust collector, such as a vacuum cleaner, that connects to the shroud. The dust collector should have filtration so dust is not re-exhausted into the environment. For hazardous dusts, the collector should include a HEPA filter.
The effectiveness of the unit will vary with the collection device so it is important that two devices are compatible and provide the right airflow for the tool design.
Three separate studies on metal grinding, auto body repair sanding, and concrete-surface grinding showed reductions in particulates between 37 to 92 percent compared with no ventilation. Though effective, tool-mounted shrouds should not be used for very dusty operation. In one of the three studies, the results were higher than the OSHA PEL and ACGIH TLV for the contaminant of concern even with a 92 percent reduction.
Most large hardware stores carry sanders with a built-in shroud that can be attached to a collection device such as a shop vacuum. There are, however, a number of companies that sell a wide variety of these devices, and many will customize shrouds for other tooling. Some of these can also provide the collection device which will attach to a variety of tools and provide the most efficient suction.
The use of tool-mounted shrouds is not without limitations. They may not provide enough reduction of dust in the air for some applications. Other methods such as wet grinding and cutting may be more effective. These devices may also generate additional noise and create ergonomic stress on the hand and wrist. It is important to try out several devices and train and familiarize the users. Tool-mounted shrouds can be more effective and less costly than traditional methods of exhaust ventilation. They should be considered in any hazard evaluation where dust is generated.
OccuSafe Industrial Hygiene & Safety, Inc. provides skills and expertise to recognize, evaluate and control hazards and injuries in the areas of industrial hygiene, occupational safety and health. OccuSafe services companies of all sizes in a range of industries.
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