What Does Short-Term Exposure Value (STEV) Mean?
A short-term exposure value (STEV) is a numeric value indicating the maximum concentration of an airborne hazardous substance to which a worker may be exposed during a limited time period. This value differs from the concentration which is deemed safe for continuous exposure of the same substance. Short-term exposure values are based on a 15-minute exposure period. The concentration level for a STEV is measured using a single air sample take during the applicable exposure period, or a time weighted average of several samples taken during the 15-minute period.
Employers must employ safety measures to address continuous exposures and STEVs because exposure to a hazardous substance at a high concentration may be harmful even if continuous exposure at a lower concentration is deemed safe.
A short-term exposure value may also be called a short-term exposure limit (STEL). The U.S. Occupational Safety and Health Administration uses the term "ceiling limit" to define short-term exposure values.
WorkplaceTesting Explains Short-Term Exposure Value (STEV)
Short-term exposure values (STEVs) are a type of workplace exposure limit. Workplace exposure limits for hazardous substances such as toxic chemicals or biological agents are used to define safe air quality standards for workplaces. In the 1970's the U.S. Occupational Safety and Health Administration (OSHA) began defining maximum workplace exposure limits for various hazardous substances. This standard was referred to as permissible exposure limits (PELs).
Subsequently, the U.S. government took steps to adopt the Threshold Limit Values (TLVs) defined by the American Conference of Governmental Industrial Hygienists (ACGIH). Other exposure limit indexes for hazardous substances include ACGIH's Biological Exposure Indices (BEIs), and the National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limits (RELs).
In general, the PEL of a substance is the concentration at which a person may be safely exposed throughout an 8-hour work day. The STEV is the maximum concentration to which a person may be exposed during a 15-minute period.