NIOSH recommends a limit of 85 dBA averaged over an 8-hour day, halving the allowed time for every 3 dB louder. OSHA’s legal limit is 90 dBA over 8 hours, halving the time only for every 5 dB louder. The gap looks small at 8 hours and grows fast. At 100 dBA, NIOSH allows 15 minutes and OSHA allows 2 hours.
If you’re an employer in the U.S., OSHA is the law you must meet. If you’re thinking about your own ears, NIOSH is the more protective and better-supported number.
NIOSH vs OSHA at a glance #
| NIOSH | OSHA | |
|---|---|---|
| Who they are | Federal research agency, part of CDC | Federal regulator, part of the Department of Labor |
| What the limit is | Recommended exposure limit (REL) | Permissible exposure limit (PEL), enforceable |
| 8-hour limit | 85 dBA | 90 dBA |
| Exchange rate | 3 dB | 5 dB |
| Hearing conservation trigger | Not applicable (recommendation) | Action level of 85 dBA 8-hour TWA |
| Impulse noise | Not covered in this comparison | 140 dB peak |
Sources: the NIOSH noise page and OSHA’s occupational noise exposure standard, 29 CFR 1910.95.
What is the NIOSH noise exposure limit? #
NIOSH’s recommended exposure limit is 85 dBA averaged over an eight-hour workday. For each 3 dBA increase in level, NIOSH recommends cutting the exposure time in half. NIOSH says workers exposed at or above the REL are at risk of significant hearing loss over their working lifetime, and it estimates that about 27 million U.S. workers are exposed to hazardous noise at work each year.
The 3 dB rule follows the physics. A 3 dB increase doubles the sound energy reaching your ear, so halving the time keeps the total energy constant. This is often called the equal-energy rule.
What is the OSHA noise exposure limit? #
OSHA’s permissible exposure limit is 90 dBA as an 8-hour time-weighted average, measured on a meter’s Slow response. Allowed time halves for every 5 dB. This is OSHA’s Table G-16:
| Sound level (dBA, slow) | OSHA permitted duration per day |
|---|---|
| 90 | 8 hours |
| 92 | 6 hours |
| 95 | 4 hours |
| 97 | 3 hours |
| 100 | 2 hours |
| 102 | 1.5 hours |
| 105 | 1 hour |
| 110 | 30 minutes |
| 115 | 15 minutes or less |
OSHA also says impulsive or impact noise should not exceed a 140 dB peak sound pressure level.
What is OSHA’s 85 dB action level? #
OSHA’s rule has a second number that matters just as much. When a worker’s exposure equals or exceeds an 8-hour TWA of 85 dBA, the employer must run a continuing hearing conservation program. That means noise monitoring, annual hearing tests, hearing protectors made available at no cost, training and recordkeeping. Hearing protectors must bring the worker’s exposure down to 90 dBA or below. For a worker whose hearing test shows a standard threshold shift, meaning a measurable loss, it’s 85 dBA or below.
So at 85 dBA both agencies agree something needs to happen. NIOSH says 85 is the limit. OSHA says 85 is the point where protection programs start, and 90 is the limit.
NIOSH vs OSHA: allowed time at the same levels #
| Level (dBA) | NIOSH | OSHA |
|---|---|---|
| 85 | 8 hours | No limit (action level) |
| 88 | 4 hours | about 10.6 hours |
| 90 | about 2.5 hours | 8 hours |
| 94 | 1 hour | about 4.6 hours |
| 95 | about 48 minutes | 4 hours |
| 100 | 15 minutes | 2 hours |
| 105 | under 5 minutes | 1 hour |
| 110 | about 1.5 minutes | 30 minutes |
NIOSH times use 8 ÷ 2^((L − 85) ÷ 3). OSHA times use the standard’s own reference-duration formula, 8 ÷ 2^((L − 90) ÷ 5).
Why are the two limits different? #
The OSHA figures are decades old and were a regulatory compromise. They’re the legal floor employers can be cited for, and changing them requires a formal rulemaking. The 5 dB exchange rate lets exposure time fall off much more slowly as noise rises.
NIOSH’s recommendation came later, in its 1998 criteria document on occupational noise, and reflects a stricter reading of the evidence on how noise damages hearing. It’s used as best practice by many safety programs, and phone and watch apps commonly use the NIOSH line. The U.S. military and many other countries also use an 85 dB limit with a 3 dB exchange rate, though you should check the specific rules that apply to you.
Which noise limit should you follow? #
- You’re an employer or safety manager in the U.S.: OSHA’s 1910.95 is the enforceable minimum, including the 85 dBA action level. Many programs design to NIOSH’s REL because it protects more workers.
- You’re a worker: your employer’s program should meet OSHA. For your own decisions about earplugs, breaks and off-the-job noise, use NIOSH.
- You’re thinking about concerts, headphones, power tools at home: use NIOSH or the WHO’s weekly safe-listening figures. OSHA’s table was never meant for recreational noise.
Remember that both limits assume the rest of your 24 hours is reasonably quiet. A loud job followed by loud headphones and a loud gym class stacks up.
How do OSHA dose and TWA work? #
Workplace noise is rarely one steady level, so OSHA combines exposures into a dose. Each period spent at a given level uses a fraction of the allowed time for that level. OSHA’s formula is D = 100 × (C1/T1 + C2/T2 + …), where C is the time actually spent at a level and T is the allowed time at that level. A dose of 100% is the PEL. OSHA converts dose to an 8-hour TWA with TWA = 16.61 × log10(D/100) + 90, and requires all sound from 80 to 130 dB to be counted in the measurement.
In practice, a dosimeter worn on the worker does this math automatically. See noise dosimeter vs sound level meter for how that differs from a spot reading.
How can you check your own exposure against NIOSH? #
For a quick personal check, Sound Meter dB shows the NIOSH-based safe exposure time for the level you’re in: 8 hours at 85 dB, halved every 3 dB, and “All day” below 80 dB. It also counts the time you’ve spent over 85 dB during a session, and its reference screen includes the full NIOSH daily exposure table. It’s a phone app, not a certified instrument, so it’s useful for awareness and deciding when to grab earplugs, not for compliance paperwork. For that, the numbers need to come from a calibrated dosimeter or Type 2 meter.
For more context, see how loud 85 dB is and when to wear hearing protection.
Frequently asked questions #
Is the OSHA noise limit 85 or 90 dB? #
Both numbers appear in the rule. 90 dBA over 8 hours is the permissible exposure limit. 85 dBA over 8 hours is the action level that requires a hearing conservation program.
What is a 3 dB exchange rate? #
It’s the rule that every 3 dB increase in level halves the time you can safely spend in it. NIOSH uses 3 dB because 3 dB doubles the sound energy. OSHA uses a 5 dB exchange rate, which allows more time at higher levels.
Is the NIOSH limit legally enforceable? #
No. NIOSH makes recommendations. OSHA sets and enforces the legal limits for most U.S. private-sector workplaces, though some states run their own OSHA-approved plans.
Does the NIOSH limit apply outside work? #
It was written for workers, but the underlying science about noise and hearing applies to anyone. It’s a reasonable personal guide for loud hobbies, events and home projects, alongside WHO’s weekly safe-listening guidance.