TLV/C is described as the maximum exposure that should never be exceeded.

• A. The max exposure that should never be exceeded
• B. The average exposure limit
• C. The exposure limit for 30 minutes only
• D. The weekly limit

Answer: (A)

TLV/C is the ceiling exposure limit—the maximum concentration that should never be exceeded at any time. It’s an instantaneous limit designed to prevent acute health effects from sudden spikes in concentration. This differs from TLV-TWA, which is the average allowed over a work shift, and TLV-STEL, the short-term exposure limit for a brief period (usually 15 minutes). It’s not an average over time, nor a 30-minute or weekly limit. In practice, when exposure approaches or hits the ceiling, actions are taken to reduce the concentration so it stays below that ceiling. That’s why the description “the maximum exposure that should never be exceeded” is the correct characterization.