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Short Term Exposure Limit (STEL)
- A Short Term Exposure Limit (STEL) is defined by ACGIH as the concentration to which workers can be exposed continuously for a short period of time without suffering from:
- chronic or irreversible tissue damage
- narcosis of sufficient degree to increase the likelihood of accidental injury, impair self-rescue or materially reduce work efficiency.
STEL's are generally used only when toxic effects have been reported from high acute (short-term) exposures in either humans or animals. An STEL is not a separate independent exposure limit, but supplements time-weighted average limits where there are recognized acute effects from a substance whose toxic effects generally chronic (long-term) in nature.
For example, one can not be exposed to an STEL concentration if the TLV-TWA (time weighted average for an 8 hour shift; see Permissible Exposure Limit (PEL)) would be exceeded. Workers can be exposed to a maximum of four STEL periods per 8 hour shift, with at least 60 minutes between exposure periods.
- "2010 TLV's and BEI's: Based on the Documentation of the Threshold Limit Values for Chemical Substances and Physical Agents & Biological Exposure Indices ...", Spiral Bound, 2010. Estimated price $49.95. Info and/or order .
- "Fundamentals of Industrial Hygiene, Fifth Edition", Hardcover, 2001, 1,100 pages. Estimated price $196.07. Info and/or order .
- "Supervisors' Safety Manual, Tenth Edition", Hardcover, 2009, 628 pages. Estimated price $138.85. Info and/or order .
In general, PEL's and TLV-STEL's appear on MSDS's in reference to substances that may be inhaled, although some can be absorbed through the skin or eyes (STEL's will often have "-skin" after them when skin exposure is possible). When working with materials that have listed exposure limits, use proper precautions to minimize the generation of a vapor or dust in the first place. Always use appropriate personal protective equipment (PPE) such as gloves, dust masks, and respirators to limit your exposure to chemicals.
Remember, exposure limits are not some magic threshold that define the border between safe and dangerous. A PEL or STEL that was acceptable in 1950 may be recognized as dangerously high today. Therefore, always do everything reasonable to limit the airborne release of chemicals or dusts in the first place.
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See also: PEL and TWA, Threshold Limit Values (TLV)
Additional definitions from Google and OneLook.
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