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Confused by the Silica “15-minute Rule”? This Might Help.

By Barb Epstien, MPH, CIH, AGC Oregon-Columbia Chapter Industrial Hygienist

drill bitWe’re sometimes asked about the so-called “15-minute rule” in the Oregon OSHA Silica Standard, so this seemed like a good place to clarify that.

For incidental tasks involving silica that may occur for 15 minutes or less on a given day, or a one-off task you don’t normally do, then you may not need to use all the specified controls or do air monitoring. Some reasons for that: historically, data has shown that we don’t usually see exposures above the eight-hour time-weighted average (TWA) Action Level for those occasional, brief exposures that are performed for only 15 minutes or less during a shift and when that’s the only potential silica exposure an employee might encounter (in other words, there is no silica exposure for the remainder of the shift). Some possible exceptions could be if the material being cut, drilled, etc. contains a very high percent of silica in it (which is why we want to see the Safety Data Sheet (SDS)). Or if the short-term task generates a lot of visible dust, then there could be high enough exposures even in that short amount of time to be of concern, which should be addressed.

Practicality is a factor, too. For a single, one-off brief task, it’s likely not feasible to implement all the controls that a longer-duration or more routine task would require. And also, a 15-minute air sample often doesn’t provide meaningful information.

However, it’s important to note that this does not allow for combining multiple short-term (less than 15-minute) tasks over a work shift. Nor can you switch out different personnel who each do the same task for less than 15 minutes, if it means that collectively the task would have a longer duration (more than 15 minutes) during a given day. That’s a misuse of the provision, and ultimately would end up causing higher silica exposures for more people. Don’t look for loopholes; understand the intent of the 15-minute rule and use it appropriately. Remember, we’re aiming for best practices, not just about being in compliance, because that’s really just the minimum. And remember that if you’re working with our around silica, you still need to have a written exposure control plan and understand and follow the other requirements of the silica standard as well.

Here’s a convenient overview of the Oregon OSHA silica rule.

Your AGC industrial hygienists or safety management consultants can help with any questions.

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