STEL is a time-weighted average concentration of a substance that workers can be exposed to for a short period (typically 15 minutes) without experiencing adverse health effects

 A Short-Term Exposure Limit (STEL) is the maximum concentration of a chemical a worker can be exposed to continuously for a short period (usually 15 minutes) without adverse health effects, and it's often expressed in parts per million (ppm) or milligrams per cubic meter (mg/m3). 

Here's a more detailed explanation:

Definition:

STEL is a time-weighted average concentration of a substance that workers can be exposed to for a short period (typically 15 minutes) without experiencing adverse health effects. 

Purpose:

STELs are designed to prevent or minimize the risk of acute (short-term) health effects from exposure to hazardous substances. 

Units:

STELs are typically expressed in parts per million (ppm) or milligrams per cubic meter (mg/m3). 

Context:

STELs are used in occupational health, industrial hygiene, and toxicology to set safe exposure limits for workers. 

Relationship to other exposure limits:

STELs are often used in conjunction with Time-Weighted Average (TWA) limits, which are based on an 8-hour workday. 

Example:

If a chemical has a STEL of 5 ppm, it means that workers should not be exposed to an average concentration of that chemical greater than 5 ppm over any 15-minute period. 

ACGIH TLV:

The American Conference of Governmental Industrial Hygienists (ACGIH) recommends Threshold Limit Values (TLVs), which include STELs, as guidance for occupational exposure limits. 

OSHA PEL:

The Occupational Safety and Health Administration (OSHA) has Permissible Exposure Limits (PELs) that are similar to TLVs, and they also include STELs.