OSHA Permissible Exposure Limit for Noise: PEL vs. Action Level (2025)

OSHA sets two noise thresholds that every employer in general industry needs to understand: the permissible exposure limit (PEL) of 90 dBA and the action level of 85 dBA. They are not the same thing, and confusing them is one of the most common compliance mistakes safety managers make. This guide explains what each threshold means, what obligations it triggers, and why you cannot ignore the lower number just because you are under the higher one.

What is the OSHA permissible exposure limit for noise?

The OSHA permissible exposure limit (PEL) for noise is 90 dBA as an 8-hour time-weighted average (TWA), defined in 29 CFR 1910.95. At or above this level, engineering and administrative controls must be implemented wherever feasible, and hearing protection use becomes mandatory.

The PEL is the legal maximum -- a worker must not be exposed above 90 dBA TWA without feasible controls being in place. It is not a safe level; it is a legal ceiling. Significant occupational hearing loss can still occur at 90 dBA over a working lifetime, which is why NIOSH and many occupational health professionals treat 85 dBA as the practical target.

What is the action level?

The action level is 85 dBA TWA, also defined in 29 CFR 1910.95. It sits 5 dB below the PEL and triggers the requirement to implement a full hearing conservation program. OSHA calls it the "action level" because it is the point at which the employer must take action -- even though no regulation has technically been violated yet.

PEL vs. action level: the key differences

What the PEL triggers

When any employee's noise exposure meets or exceeds 90 dBA TWA, OSHA requires:

• Feasible engineering controls -- such as noise enclosures, vibration isolation, substituting quieter equipment, or redesigning processes to reduce noise at the source
• Feasible administrative controls -- such as rotating workers through noisy areas to reduce individual exposure times, scheduling noisy work during off-hours, or creating quiet rest areas
• Mandatory hearing protection use -- workers at or above the PEL must wear hearing protection, not just have it available
• Verification that HPDs are adequate -- the selected device must attenuate exposure to at least 90 dBA (or 85 dBA for workers with a standard threshold shift)

What the action level triggers

When any employee's noise exposure meets or exceeds 85 dBA TWA, the employer must implement and maintain a continuing, effective hearing conservation program that includes all six required components:

• Noise monitoring (Section 1910.95(d))
• Audiometric testing -- baseline and annual (Section 1910.95(g))
• Hearing protection -- available at no cost, variety of choices (Section 1910.95(i))
• Annual training (Section 1910.95(k))
• Recordkeeping -- monitoring records 2 years; audiometric records for duration of employment (Section 1910.95(m))
• Employee access to information and the standard (Section 1910.95(l))

Importantly, being below the PEL does not eliminate any of these requirements. A facility running at 87 dBA TWA is below the PEL -- but has crossed the action level and must operate a full hearing conservation program.

The 5 dBA exchange rate and dose calculation

OSHA uses a 5 dBA exchange rate (also called a doubling rate): every 5 dB increase in noise level halves the allowable exposure duration. This is built into the dose formula for calculating TWA across a shift with varying noise levels.

A worker who spends time in areas of varying noise accumulates a dose throughout the shift. The dose percentage is calculated as the sum of each exposure duration divided by its maximum permitted duration. A dose of 50% or more at the 5 dBA exchange rate equals an 8-hour TWA of 85 dBA -- the action level. A dose of 100% equals 90 dBA TWA -- the PEL.

Engineering and administrative controls: when are they required?

Engineering and administrative controls are only mandated by OSHA once exposure reaches the PEL (90 dBA TWA). Below the PEL -- even if above the action level -- controls are not legally required, though they represent best practice.

Engineering controls (preferred)

These reduce noise at the source and include: machinery enclosures and noise barriers, vibration damping, substituting quieter processes or equipment, acoustic treatment of work areas, and isolating noisy equipment from workers. Engineering controls are preferred because they reduce exposure for all workers regardless of whether they are wearing PPE.

Administrative controls

These reduce individual exposure through work organization: job rotation, limiting time in high-noise areas, scheduling noisy tasks during low-occupancy periods, and creating quiet break areas. Administrative controls do not eliminate the hazard -- they just limit how long any one person is exposed to it.

OSHA PEL vs. NIOSH REL: which standard is stricter?

NIOSH's stricter 3 dBA exchange rate means that every 3 dB increase in noise halves the allowable duration -- compared to OSHA's 5 dB. In practice, NIOSH's approach results in significantly lower calculated doses for workers in variable noise environments, and stricter program requirements kick in at lower levels. Many occupational health professionals and EHS consultants design programs to meet NIOSH standards as best practice even when OSHA compliance is the legal floor.

Common PEL compliance mistakes

• Assuming "below PEL = no program needed." The action level at 85 dBA triggers the full hearing conservation program. Workers at 87 dBA TWA need audiograms, training, and records -- even though they are technically below the PEL.
• Measuring only peak noise, not TWA. A machine that hits 100 dBA during operation may produce a TWA well below 90 dBA if workers are only exposed for short periods. Conversely, moderate but sustained noise across a full shift can push the TWA above the PEL even when no single source sounds unusually loud.
• Counting hearing protection as a substitute for engineering controls. Above the PEL, feasible engineering and administrative controls must be explored first. PPE is supplementary, not a replacement for structural noise reduction.
• Failing to re-monitor after process or equipment changes. OSHA requires new monitoring whenever changes could increase noise exposures. Installing a new press, adding a packaging line, or expanding production shifts the baseline.
• Using the wrong exchange rate. Some older monitoring equipment defaults to a 3 dBA exchange rate (NIOSH). OSHA compliance requires calculations using the 5 dBA exchange rate. Using the wrong rate overstates or understates dose.

Frequently asked questions