Short-Term Exposure Limit (STEL) is defined as the concentration which workers can be exposed for a short period without suffering from irritation, tissue damage, or narcosis.

• A. A limit used to evaluate long-term chronic exposure.
• B. The average concentration over 8 hours.
• C. The maximum permissible exposure during a 24-hour period.
• D. The concentration which workers can be exposed for a short period without suffering from irritation, tissue damage, or narcosis.

Answer: (C)

Short-Term Exposure Limit is about guarding against acute effects from brief spikes in exposure. It defines the concentration a worker can be exposed to for a short period (typically around 15 minutes) without suffering irritation, tissue damage, or narcosis. This kind of limit is specifically intended to prevent immediate harm from transient high concentrations, not to describe how a substance affects someone over an entire day or over many days.

A limit described as a long-term chronic exposure, or as an 8-hour average (time-weighted average), or as a 24-hour maximum, addresses different patterns of exposure over longer periods. STEL focuses on the short-term window to prevent acute health effects, which is why the statement describing a short-term exposure limit best fits the concept.