Under OSHA’s general industry rule (29 CFR 1910.95), hearing protection must be made available once your 8-hour time-weighted average noise exposure reaches 85 dBA, and wearing it becomes mandatory at 90 dBA. So the honest answer to “at what decibel is hearing protection required” is that there are two decibel thresholds, not one, and the obligations at each are different. A third rule sits on top: if your hearing has already shifted, mandatory protection kicks in at 85 dBA instead of 90.
What “90 dBA” Actually Means
OSHA does not measure the loudest moment of your shift. It measures your total noise dose across an 8-hour workday, expressed as a time-weighted average (TWA) on the A-weighted decibel scale. Steady 90 dBA for eight hours and a mixed shift with the same total sound energy produce the same TWA.
The standard uses a 5 dB exchange rate. Every 5 dB increase in noise cuts the allowable exposure time in half. Eight hours at 90 dBA. Four hours at 95. Two hours at 100. If your shift moves between levels, your employer adds up the fraction of time spent at each noise level divided by the maximum time allowed at that level; a total over 1.0 means you have exceeded the limit.1Occupational Safety and Health Administration. Occupational Noise Exposure – 1910.95
This matters for the “at what decibel” question because a sound-level meter reading of 95 dBA at your workstation does not automatically mean you are over the limit. It means you are over the limit if you spend more than four hours there.
The 85 dBA Action Level
The first threshold that triggers employer duties is the action level: an 8-hour TWA of 85 dBA, sometimes called a 50% noise dose. Once any employee reaches this level, the employer must launch a hearing conservation program, which includes noise monitoring, annual hearing tests, access to hearing protection, and training on how noise damages hearing.1Occupational Safety and Health Administration. Occupational Noise Exposure – 1910.95
At 85 dBA, wearing hearing protection is voluntary. Your employer has to give you protectors at no cost and show you how to use them, but the decision to put them in is yours. Your employer also has to tell you your monitoring results whenever your exposure meets or exceeds the action level. The rule requires notification but does not set a number of days.
Mandatory Protection at 90 dBA
The permissible exposure limit (PEL) is an 8-hour TWA of 90 dBA. At this level, hearing protection is no longer optional. But protectors are not the first move. Employers must first try to bring the noise down through engineering controls (quieter tools, better maintenance, sound barriers, enclosing loud equipment) or administrative controls (rotating workers, shortening shifts at loud tasks).2Occupational Safety and Health Administration. Occupational Noise Exposure – Exposure and Controls Hearing protection fills whatever gap those measures cannot close.1Occupational Safety and Health Administration. Occupational Noise Exposure – 1910.95
How Long You Can Be Exposed at Each Level
Table G-16 in the standard sets the maximum permissible time at each noise level:1Occupational Safety and Health Administration. Occupational Noise Exposure – 1910.95
- 90 dBA: 8 hours
- 92 dBA: 6 hours
- 95 dBA: 4 hours
- 97 dBA: 3 hours
- 100 dBA: 2 hours
- 102 dBA: 1.5 hours
- 105 dBA: 1 hour
- 110 dBA: 30 minutes
- 115 dBA: 15 minutes or less
No continuous or intermittent exposure above 115 dBA is permitted beyond that 15-minute window. Impulsive or impact noise (a sudden blast rather than sustained sound) must never exceed 140 dB peak sound pressure level.
When Protection Becomes Mandatory at 85 dBA Instead of 90
The 90 dBA threshold applies to workers whose hearing has not shifted. If your annual audiogram shows a standard threshold shift (STS), the rules tighten for you individually.
An STS is a measurable decline in hearing: an average worsening of 10 dB or more at 2,000, 3,000, and 4,000 Hz in either ear compared with your baseline audiogram.3Occupational Safety and Health Administration. Recording Criteria for Cases Involving Occupational Hearing Loss – 1904.10 Once an STS is confirmed, your employer must notify you in writing within 21 days.4Occupational Safety and Health Administration. Notification Requirements for Standard Threshold Shifts If you were not already wearing hearing protection, you must start. If you were, your employer must refit you, retrain you, or provide a better protector.
The critical piece: after an STS, your hearing protection must bring your exposure down to an 8-hour TWA of 85 dBA or below, not the 90 dBA that applies to workers with normal hearing.5Occupational Safety and Health Administration. Methods for Estimating the Adequacy of Hearing Protector Attenuation – Appendix B A worker at 88 dBA with no hearing changes has no mandatory protection requirement. That same worker at 88 dBA with a confirmed STS must be protected down to 85 dBA.
Checking Whether Your Hearing Protector Is Enough
Every hearing protector sold in the U.S. carries a Noise Reduction Rating (NRR) on the label, set under EPA rules based on laboratory testing. Real-world performance is lower, so OSHA applies a derating formula.
When your noise measurement is in A-weighted decibels, subtract 7 dB from the NRR, then subtract that adjusted number from your TWA. A TWA of 100 dBA with earplugs rated NRR 29 gives you (29 − 7) = 22 dB of protection, bringing your effective exposure to 78 dBA. OSHA compliance officers apply an additional 50% safety factor to that adjusted NRR when deciding whether engineering controls should be required, but that extra cut does not apply when judging hearing protector adequacy under the conservation program.6Occupational Safety and Health Administration. Application of the Environmental Protection Agency NRR
If C-weighted measurements are available, just subtract the full NRR from the C-weighted TWA.5Occupational Safety and Health Administration. Methods for Estimating the Adequacy of Hearing Protector Attenuation – Appendix B
When a single protector cannot bring exposure below the required level, dual protection (earplugs plus earmuffs) is necessary. The rule sets no fixed decibel trigger. The requirement kicks in whenever the math shows that one device alone cannot reduce your exposure to 90 dBA (or 85 dBA after an STS). That situation typically appears somewhere above 100 to 105 dBA TWA, depending on which devices are available.
Construction Workers Are Covered by a Different Rule
If you work in construction, your protection is governed by 29 CFR 1926.52 rather than the general industry standard. The permissible exposure limits are identical (90 dBA for 8 hours, the same table of shorter durations at higher levels, and the same 140 dB peak limit on impulsive noise).7eCFR. 29 CFR 1926.52 – Occupational Noise Exposure
What differs is everything below the PEL. The construction standard has no 85 dBA action level, no required hearing conservation program, no mandatory annual audiometric testing, and no annual training requirement. When noise cannot be reduced through engineering or administrative controls, the employer must provide ear protection, and any earplugs must be individually fitted by a competent person.8eCFR. 29 CFR 1926.101 – Hearing Protection If you work construction, you will not get annual hearing tests unless your employer chooses to provide them.
What to Do If Your Employer Ignores the Rule
If your employer is not monitoring noise, is not providing hearing protection where the standard requires it, or is running noise levels above the PEL without controls, you can file a complaint with OSHA online, by phone, or by mail, and you can ask that your name be withheld from the employer.
If your employer retaliates against you for raising noise concerns or filing a complaint, Section 11(c) of the OSH Act protects you from discharge or discrimination. You have 30 days from the retaliatory action to file a whistleblower complaint with OSHA.9Whistleblowers.gov. Occupational Safety and Health Act, Section 11(c) That clock runs from the retaliation itself, not from when you first raised the noise issue, so it moves faster than most people expect.