Final answer:
The STEL (Short-Term Exposure Limit) is the 15-minute time-weighted average exposure limit that should not be exceeded at any point during the workday. It is specific to short term exposures and is measured over a 15-minute period to prevent acute health effects.
Step-by-step explanation:
The 15-minute time-weighted average exposure which cannot be exceeded at any point during the workday is known as the STEL (Short-Term Exposure Limit). This limit pertains to the concentration of a substance in the air and is established to protect workers from the health risks associated with high levels of exposure over a short period. The STEL complements other exposure limits such as the PEL (Permissible Exposure Limit) which is the maximum amount of a substance that a worker can be exposed to over an 8-hour workday, and the TLV (Threshold Limit Value), an occupational exposure limit recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). Unlike these, the CEL (Ceiling Limit) is a limit that must not be exceeded at any time and is considered an instantaneous limit.