OSHA Noise Exposure — 29 CFR 1910.95
OSHA 29 CFR 1910.95 sets the permissible exposure limit (PEL) at 90 dBA TWA for 8 hours using a 5 dB exchange rate. The 85 dBA action level triggers mandatory hearing conservation including audiometric testing, hearing protection, and employee training.
PEL
90 dBA TWA for 8 hours. 5 dB exchange rate: each 5 dB increase halves permitted time. 95 dBA = 4 hours, 100 dBA = 2 hours, 105 dBA = 1 hour per Table G-16.
Action Level
85 dBA TWA triggers hearing conservation per 1910.95(c): monitoring, audiometric testing, hearing protection, training. Program continues while any employee reaches the action level.
Dose Calculation
D = 100 times sum of (C_i/T_i). 100% = 90 dBA TWA. TWA = 16.61 log(D/100) + 90. Exposures below 80 dBA excluded per OSHA methodology.
OSHA vs NIOSH
NIOSH: 85 dBA REL with 3 dB exchange (scientifically more accurate). At 88 dBA: OSHA allows 8 hours, NIOSH allows 4. Most international standards use 3 dB.
Hearing Protection
OSHA derates NRR by 50%: effective = (NRR-7)/2 in dBA. NRR 29 earplug = approximately 11 dBA real-world reduction. Dual protection adds 5 dB to higher-rated device.
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Calculate OSHA noise dose and TWA