ACGIH STEL Region applies to compounds lacking which two exposure concepts?

ACGIH STEL Region applies to compounds lacking which two exposure concepts?

• A. PEL and TLV
• B. STEL and Ceiling
• C. Action Level and PEL
• D. TLV and Action Level

Answer: (B)

The main idea is that some chemicals don’t have all three ACGIH exposure concepts defined. The STEL Region is used for substances that do not have a Short-Term Exposure Limit (STEL) and do not have a Ceiling value defined. In these cases, only a TLV-TWA is provided, so you would rely on the time-weighted average limit and still need controls to keep exposures below that level, but there’s no short-term or ceiling limit to reference. That’s why the two concepts that are missing for these chemicals are the STEL and the Ceiling. The other options mix OSHA terms or imply missing TLV or other concepts, which isn’t what the STEL Region addresses.

The main idea is that some chemicals don’t have all three ACGIH exposure concepts defined. The STEL Region is used for substances that do not have a Short-Term Exposure Limit (STEL) and do not have a Ceiling value defined. In these cases, only a TLV-TWA is provided, so you would rely on the time-weighted average limit and still need controls to keep exposures below that level, but there’s no short-term or ceiling limit to reference. That’s why the two concepts that are missing for these chemicals are the STEL and the Ceiling. The other options mix OSHA terms or imply missing TLV or other concepts, which isn’t what the STEL Region addresses.