STEL stands for Short-Term Exposure Limit. This is the amount, or concentration, of a particular substance that someone can be exposed to continuously for a 15-minute length of time without being at risk of harm. The term is used throughout many different industries, especially those that regularly work with different substances that can be harmful to exposure.
When determining what the STEL is for a particular substance, testers will need to look at a time-weighted average of 15 minutes. If there is any risk of irritation, long-term tissue damage, or necrosis to a degree that will cause an increase in the risk of accidental injury, then it is above the STEL. This measurement has been done for many different types of substances so that facilities can typically look up what the STEL is for something that they will be using within their facility.
Understanding what the STEL is for a particular substance is important for determining how that substance should be used. If someone is only going to be exposed to it for a very brief period, then no additional precautions need to be taken. If, however, there will be exposure that is prolonged or repeated regularly, efforts must be taken to keep people safe.
One of the most common ways that facilities keep employees safe when they will be around a substance for longer than the STEL is to provide personal protection equipment (PPE). This can help to eliminate the actual exposure so that they are not at risk. It is generally a good practice to use PPE even if exposure is not expected to last a full 15 minutes.
