Allowed hours by sound level
| Sound level | Reference duration T | Dose for a full 8-hour shift |
|---|---|---|
| 80 dBA | 32 h | 25% |
| 85 dBA | 16 h | 50% |
| 88 dBA | 10.56 h | 75.8% |
| 90 dBA | 8 h | 100% |
| 92 dBA | 6.06 h | 132% |
| 94 dBA | 4.59 h | 174.1% |
| 95 dBA | 4 h | 200% |
| 97 dBA | 3.03 h | 263.9% |
| 100 dBA | 2 h | 400% |
| 102 dBA | 1.52 h | 527.8% |
| 105 dBA | 1 h | 800% |
| 110 dBA | 30 min | 1600% |
| 115 dBA | 15 min | 3200% |
T = 8 ÷ 2(L − 90) / 5 hours — the values of Table G-16a in Appendix A, which lists 80 to 130 dB.
How the numbers are worked out
- Dose = 100 × (C1/T1 + C2/T2 + …), where C is the hours at a level and T is the reference duration for that level (Appendix A). All levels from 80 to 130 dB count (1910.95(d)(2)(i)).
- TWA = 16.61 × log10(dose ÷ 100) + 90. A 50% dose equals 85 dBA.
- Action level — a TWA of 85 dBA or a 50% dose. At or above it the employer needs a hearing conservation program (1910.95(c)).
- Permissible exposure limit — Table G-16 starts at 90 dBA for 8 hours, so this page adds up only levels of 90 dBA and above for the limit. If that sum is over 100%, the exposure exceeds the limit and controls or hearing protection are required (1910.95(b)).
- Exposure above 115 dBA is not allowed, and impulse or impact noise should not exceed 140 dB peak.
What this page doesn't cover
- Octave-band conversion (Figure G-9), dosimeter settings and hearing protector attenuation.
- Construction (29 CFR 1926.52), mining (MSHA) and the stricter NIOSH recommendation (85 dBA with a 3 dB exchange rate).
This page is for reference. Workplace compliance should be based on measured exposure and the full text of 29 CFR 1910.95.
Frequently asked questions
What is a noise dose?
It is the share of the allowed daily noise exposure a worker received. For each sound level, divide the hours spent there by the reference duration for that level, add the fractions and multiply by 100 (29 CFR 1910.95 Appendix A). 100% equals 8 hours at 90 dBA.
What is the OSHA action level for noise?
An 8-hour time-weighted average of 85 dBA, or a dose of 50%. At or above it, the employer must run a hearing conservation program — monitoring, audiometric testing, hearing protectors and training (29 CFR 1910.95(c)).
How long can a worker be exposed to 95 dBA?
Four hours a day under the OSHA permissible exposure limit. Each 5 dB increase halves the allowed time: 8 hours at 90 dBA, 4 at 95, 2 at 100, 1 at 105 (Table G-16). Exposure above 115 dBA is not permitted, and impulse noise should not exceed 140 dB peak.
How do I convert a dose to TWA?
TWA = 16.61 × log10(dose ÷ 100) + 90. A 50% dose is 85 dBA, 100% is 90 dBA and 200% is 95 dBA (Appendix A).