The allowable Time-Weighted Average concentration for a normal 8-hour workday or 40-hour workweek.

Threshold limit value-time-weighted average. Usually timed over an 8 hour work day or 40 hour work week.

Threshold Limit Value - Time-Weighted Average: The time-weighted average concentration for a normal 8 hour work day and a 40 hour work week, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect.

Time Weighted Average - The average amount of gas (in PPM) a worker can be exposed to over a certain time period. This time is defined as 8 hours to represent a normal work day.

The time-weighted average concentration of a refrigerant or other chemical in air for a normal 8-hour workday and a 40-hour workweek, to which nearly all workers are repeatedly exposed, day after day, without adverse effects, as adopted by the American Conference of Government Industrial Hygienists (ACGIH).