also uses the same 5 decibel exchange rate and 90 dBA for an 8-hour TWA for their PEL. Once a miner's noise exposure exceeds the PEL, feasible engineering AND administrative controls must be in place to try to limit the noise exposure of the employees. If a mine operator uses administrative controls, procedures for such controls must be posted on the bulletin board and a copy must be supplied to all affected employees. NIOSH The National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL) for noise exposure uses a 3 decibel exchange rate. The recommendation for occupational noise exposure is 85 decibels (dBA) for an 8-hour TWA. For every 3 dB over 85, the exposure time is cut in half. NIOSH reports exposures above this level are considered hazardous. NIOSH uses a hierarchy of control to reduce or remove hazardous noise. See also Mine Safety and Health Administration National Institute for Occupational Safety and Health Recommended exposure limit Threshold limit value published by ACGIH Occupational exposure banding References External links Permissible Exposure Limits – Annotated Tables (Permissible Exposure Limits – Annotated Tables) 1988 OSHA PEL Project Documentation: List by Chemical Name Available from NIOSH ACGIH website ACGIH website Workplace Environmental Exposure Limits (WEEL™) Values available on-line through The Occupational Alliance for Risk Science - Workplace Environmental Exposure Levels (WEEL)™ Chemical safety Concentration indicators Environmental standards National Institute for Occupational Safety and Health Occupational Safety and Health Administration