Threshold Limit Value-Time-Weighted Average (TLV-TWA): The time-weighted average
concentration for a normal 8-hour workday and a 40-hour workweek to which nearly all workers
may be repeatedly exposed, day after day, without adverse effects.
Toxic Atmosphere: An atmosphere containing a concentration of a substance above the
published or otherwise known safe levels, such as the Threshold Limit Value, Permissible
Exposure Limit, Recommended Exposure Limit, or the Immediately Dangerous to Life or Health
Work: The process of performing a defined task or activity; for example, research and
development, operations, maintenance and repair, administration, software development and use,
inspection, safeguards and security, data collection, and analysis.
Work Plan: That part of a comprehensive Site Health and Safety Program which addresses the
tasks and objectives of site operations, including logistics and resources.