 Mining equipment can generate considerable noise, putting workers at risk for hearing loss.Cave-ins, rock falls, and exposure to excess heat are also known hazards.The current NIOSH Recommended Exposure Limit (REL) of noise is 85 dBA with a 3 dBA exchange rate and the MSHA Permissible Exposure Limit (PEL) is 90 dBA with a 5 dBA exchange rate as an 8-hour time-weighted average.