ACGIH STEL is defined as concentrations above the TLV but below the upper concentration level defined as the STEL limit.

ACGIH STEL is defined as concentrations above the TLV but below the upper concentration level defined as the STEL limit.

• A. The PEL
• B. The action level
• C. The TLV
• D. The STEL limit

Answer: (D)

Short-term exposure limit defines the maximum concentration workers can be exposed to for a brief period (typically about 15 minutes) to avoid acute health effects. It sits above the long‑term TLV-TWA value because it protects against spikes that could cause immediate harm, while still capping exposures during short durations. The STEL is the upper concentration boundary used for these short-term exposures, so the correct choice is the STEL limit—it represents that upper cap. This differs from the TLV, which is the recommended limit for an 8-hour work shift (a long-term reference). It’s also not the regulatory PEL or an action level, which triggers controls or monitoring rather than serving as a short-term exposure cap.

Short-term exposure limit defines the maximum concentration workers can be exposed to for a brief period (typically about 15 minutes) to avoid acute health effects. It sits above the long‑term TLV-TWA value because it protects against spikes that could cause immediate harm, while still capping exposures during short durations. The STEL is the upper concentration boundary used for these short-term exposures, so the correct choice is the STEL limit—it represents that upper cap.

This differs from the TLV, which is the recommended limit for an 8-hour work shift (a long-term reference). It’s also not the regulatory PEL or an action level, which triggers controls or monitoring rather than serving as a short-term exposure cap.