The OSHA action level for noise exposure is 85 dBA as an 8-hour time-weighted average — and it is the trigger for the full hearing conservation program requirement under 29 CFR 1910.95(c). The CDC estimates 22 million U.S. workers are exposed to hazardous noise at work each year — making this the most consequential threshold in occupational health compliance. Not 90 dBA. The permissible exposure limit (PEL) is 90 dBA, which triggers engineering control requirements. But the hearing conservation program — noise monitoring, audiometric testing, hearing protection, training, recordkeeping — all attach at 85 dBA. This is the single most common misunderstanding among employers covered by 1910.95.
Soundtrace noise monitoring calculates worker TWA and automatically flags employees at or above the 85 dBA action level for enrollment in a complete OSHA 1910.95 hearing conservation program.
What the Action Level Is and What It Triggers
The action level under OSHA 1910.95(c) is 85 dBA as an 8-hour time-weighted average. When any employee’s noise exposure meets or exceeds this threshold, the employer must implement all six elements of a hearing conservation program:
- Noise monitoring to measure and document exposures
- Audiometric testing (baseline and annual audiograms)
- Hearing protection devices provided at no cost in a variety of styles
- Annual employee training on noise, HPDs, and audiometric testing
- Recordkeeping for noise measurements and audiograms
- Employee access to monitoring results and audiometric records
Many employers believe the hearing conservation program only kicks in at 90 dBA — the permissible exposure limit. It does not. The program requirement attaches at 85 dBA TWA. Workers exposed between 85 and 90 dBA are legally below the PEL but still require a full HCP. A facility with steady-state noise of 87 dBA and no hearing conservation program is out of compliance.
Action Level vs. PEL: What Each Requires
| Threshold | Level | What It Triggers |
|---|---|---|
| Action Level (AL) | 85 dBA TWA | Full 6-element hearing conservation program required for all enrolled workers |
| Permissible Exposure Limit (PEL) | 90 dBA TWA | Engineering and administrative controls required; HPD use becomes mandatory (not just available) |
The distinction matters operationally. At the action level, an employer must make HPDs available and encourage their use. At the PEL, HPD use is mandatory and engineering controls (noise isolation, equipment modification, process changes) must be implemented where feasible. Workers above the PEL who still exceed 90 dBA even with engineering controls must use HPDs with a derated NRR sufficient to reduce their effective exposure to below 90 dBA.
▶ Bottom line: if anyone in your facility is regularly at or above 85 dBA for an 8-hour shift, you need a full hearing conservation program. See: OSHA 1910.95 Requirements: All 6 Elements Explained.
How TWA and Noise Dose Are Calculated
OSHA measures noise exposure as a time-weighted average (TWA) — the average sound level over an 8-hour workday, weighted for the actual time spent at each noise level. The calculation uses a 90 dBA criterion level and a 5 dB exchange rate (also called a doubling rate): every 5 dB increase in level halves the permissible exposure time.
| Noise Level | Permissible Duration (OSHA) |
|---|---|
| 90 dBA | 8 hours |
| 95 dBA | 4 hours |
| 100 dBA | 2 hours |
| 105 dBA | 1 hour |
| 110 dBA | 30 minutes |
| 115 dBA | 15 minutes (maximum) |
Noise dose is expressed as a percentage. 100% dose = PEL (90 dBA TWA). 50% dose = action level (85 dBA TWA). A worker who spends 4 hours at 95 dBA has a dose of 100% (4 hours / 4 hour limit = 1.0 = 100%). Add 2 hours at 90 dBA and the dose climbs to 125% — exceeding the PEL.
NIOSH uses a 3 dB exchange rate (equal energy principle) rather than OSHA’s 5 dB rate. This produces significantly higher dose calculations for the same exposures — particularly at moderate levels (85–95 dBA). A worker OSHA calculates at 80% dose may be calculated at 200%+ under NIOSH criteria. See: NIOSH vs. OSHA Noise Exposure Limits: PEL, REL, and Exchange Rate Explained.
Calculate Whether Your Workers Reach the Action Level
Enter the noise levels and durations for a typical shift. The calculator uses OSHA’s 90 dBA criterion level and 5 dB exchange rate to compute total dose — and tells you whether the 85 dBA action level or 90 dBA PEL is met, and what that triggers.
OSHA calculates dose as the sum of (time at level / permissible time at level) using a 90 dBA criterion and 5 dB exchange rate. Dose ≥50% (equivalent to 85 dBA TWA) triggers the hearing conservation program. Dose ≥100% exceeds the PEL.
How Noise Monitoring Determines Action Level Exposure
OSHA 1910.95(d) requires noise monitoring whenever employee exposures may equal or exceed the 85 dBA action level. Two methods are permitted: area monitoring (sound level measurements at fixed positions) and personal dosimetry (exposure measured at the worker’s ear level). OSHA recommends personal dosimetry when workers move between areas of different noise levels during a shift, because area monitoring may significantly underestimate or overestimate individual TWA. See: Area Monitoring vs. Personal Noise Monitoring: OSHA Guide.
Monitoring must be repeated whenever changes in production, process, equipment, or noise controls may affect exposures. Employers who install new equipment or change production processes without re-monitoring are out of compliance even if their original survey was done correctly — this is one of the most commonly cited monitoring deficiencies in OSHA inspections.
Workers must be notified of monitoring results and must be allowed to observe monitoring procedures. Records must be retained for 2 years. See: Noise Monitoring & Recordkeeping: OSHA Requirements.
For workers who move between a 95 dBA production floor and a 75 dBA break room, area monitoring at a single position would significantly overestimate or underestimate individual exposure depending on where the monitor is placed. Personal dosimetry worn at the worker’s collar captures actual individual TWA regardless of movement — which is why it is the preferred method for highly mobile workers in variable-noise environments.
Frequently Asked Questions
The OSHA action level is 85 dBA as an 8-hour time-weighted average under 29 CFR 1910.95(c). At or above this level, employers must implement a full hearing conservation program. The action level is separate from the permissible exposure limit (PEL) of 90 dBA TWA, which triggers additional engineering control requirements.
The action level (85 dBA TWA) triggers the hearing conservation program. The PEL (90 dBA TWA) triggers engineering and administrative control requirements on top of the HCP. Workers between 85 and 90 dBA require a full HCP even though they are below the PEL. HPD use is mandatory above the PEL, and available (not mandatory) between the action level and PEL — unless the worker has a prior STS.
OSHA noise dose is the sum of (time at each level / permissible time at that level) using a 90 dBA criterion and 5 dB exchange rate. 100% dose = PEL. 50% dose = action level. Doses from multiple exposures are additive. A worker spending 4 hours at 95 dBA has a 100% dose from that single exposure alone.
A full six-element program is required when any employee’s noise exposure equals or exceeds 85 dBA TWA — the action level under 1910.95(c). The six elements are: noise monitoring, audiometric testing, hearing protection devices at no cost, annual training, recordkeeping, and employee access to records and monitoring results.
No. Engineering and administrative controls are required when exposures exceed the PEL of 90 dBA TWA. At the action level (85 dBA TWA), only the six hearing conservation program elements are required. Engineering controls become mandatory at the PEL — and must be implemented where feasible before relying solely on HPDs.
Know exactly who’s at or above 85 dBA
Soundtrace noise monitoring calculates worker TWA, flags action level and PEL exposures, and automatically triggers HCP enrollment — so nothing falls through the cracks.
Schedule a Demo Get a quote for your facility →- OSHA Hearing Conservation Program: The Complete Guide
- OSHA 1910.95 Requirements: All 6 Elements Explained
- NIOSH vs. OSHA Noise Exposure Limits: PEL, REL, and Exchange Rate
- Noise Monitoring & Recordkeeping: OSHA Requirements
- Area Monitoring vs. Personal Noise Monitoring
- OSHA Hearing Conservation Violations: Penalties & Citations