TLV/TWA is defined as the maximum concentration a person may be exposed for 8 hours per day/40 hours per week.

TLV/TWA is defined as the maximum concentration a person may be exposed for 8 hours per day/40 hours per week.

• A. The maximum acceptable exposure in any 8-hour period
• B. The average exposure limit over a workweek
• C. The max concentration a person may be exposed for 8 hours per day/40 hours per week
• D. The ceiling limit that should never be exceeded

Answer: (C)

Time-Weighted Average answers the idea that exposure can vary during a shift, but we’re looking at the average concentration over a standard work period. TLV/TWA is the maximum average concentration a person may be exposed to, averaged over an 8-hour workday or a 40-hour workweek. Short spikes above the limit are allowed as long as the overall average remains at or below that value. This differs from a ceiling limit, which is an instantaneous concentration that should never be exceeded, and from a simple weekly average that doesn’t tie the limit to the 8-hour workday reference. TLV-TWA is a guideline used to protect workers by accounting for fluctuations in exposure over typical work schedules.

Time-Weighted Average answers the idea that exposure can vary during a shift, but we’re looking at the average concentration over a standard work period. TLV/TWA is the maximum average concentration a person may be exposed to, averaged over an 8-hour workday or a 40-hour workweek. Short spikes above the limit are allowed as long as the overall average remains at or below that value. This differs from a ceiling limit, which is an instantaneous concentration that should never be exceeded, and from a simple weekly average that doesn’t tie the limit to the 8-hour workday reference. TLV-TWA is a guideline used to protect workers by accounting for fluctuations in exposure over typical work schedules.