Which term describes the concentration that must not be exceeded in the workplace for an 8-hour period?

• A. Permissible Exposure Limit
• B. Threshold Limit Value - Time Weighted Average
• C. Odor Threshold
• D. Ceiling

Answer: (A)

The key idea is the maximum safe concentration over a full workday. Permissible Exposure Limit is the regulatory limit on how much of a substance workers can be exposed to in the air, averaged over an 8-hour shift. It’s set to protect workers during a typical workday, recognizing that exposures can vary from moment to moment. This is usually enforced by safety regulations and used to guide protections like ventilation and PPE.

A TLV-TWA is a similar guideline, but it’s a recommended limit from professionals rather than a binding regulation. Odor threshold isn’t about safety limits at all; it’s simply the concentration at which a substance’s smell becomes detectable. A ceiling limit is the maximum concentration that should never be exceeded at any time, not averaged over 8 hours.