What Does Time-Weighted Average (TWA) Mean?
A time-weighted average (TWA) refers to the average rate at which a worker is exposed to a contaminant or adverse condition (such as noise) without unpleasant or dire effects over a defined period such as an 8-hour day or 40-hour work week. Commonly, the time-weighted average is calculated to confirm that the concentration of a potentially hazardous substance during a normal 8 to 10 hour work day will not exceed regulatory or legal standards. Staying below a specified time-weighted average may also reduce the corrosion rate due to the presence of said substances.
