Noise
Action Level (AL) and Permissible Exposure Limit (PEL)
OSHA 29 CFR 1910.95 – Occupational Noise Exposure requires employers to protect workers from hazardous noise. The requirements differ depending on whether exposure is at or above 85 dBA (action level) or 90 dBA (PEL) averaged over an 8-hour work shift.
Noise Monitoring
As detailed below, at 85 dBA average over an 8-hour period, employers must start a Hearing Conservation Program. If employees are exposed to 90 dBA or more during the 8-hour period, employers are required to actively reduce noise exposure and enforce the use of hearing protection if exposure levels cannot be reduced below 90 dBA.
📉 85 dBA (Action Level)
- Hearing Conservation Program: Must be implemented for all exposed workers.
- Audiometric Testing: Provide baseline and annual hearing tests.
- Training: Conduct annual training on noise hazards and hearing protection.
- Hearing Protection: Provide HPDs (earplugs, earmuffs) at no cost and ensure proper fit.
- Recordkeeping: Keep records of noise exposure and hearing tests.
⚠️ 90 dBA (Permissible Exposure Limit – PEL)
- Exposure Reduction: Use engineering controls (quiet equipment, barriers) and administrative controls (job rotation, time limits).
- Mandatory Hearing Protection: Workers must use HPDs if noise cannot be reduced below 90 dBA.
- Hearing Conservation Program: Continue full program requirements from 85 dBA level.
- Testing & Training: Provide annual audiometric testing and noise hazard training.
- Recordkeeping: Maintain compliance and monitoring documentation.
Example: Using the table below, a industrial hygienist calculates the daily noise exposure of a monitored worker who works in three different departments throughout an 8-hour work period.
This calculation answers the question: "Does the worker require mandatory hearing protection?"
| Example: Worker's Activity | Time | Measured Sound Level |
|---|---|---|
| Equipment maintenance | 6:00 a.m. – 8:00 a.m. (2 hours) | 85 dBA |
| Milling assist | 8:00 a.m. – 10:00 a.m. (2 hours) | 90 dBA |
| Lunch Break | 10:00 a.m. – 11:00 a.m. (1 hour) | 65 dBA (Excluded) |
| Milling machine | 11:00 a.m. – 2:00 p.m. (3 hours) | 95 dBA |
The permissible noise exposure durations for the calculation are based on OSHA 1910.95 Table G-16.
- 90 dBA exposure while performing equipment maintenance for 2 hours (8 hours permissible)
- 90 dBA exposure while performing milling assistance for 2 hours (8 hours permissible)
- 95 dBA exposure while working at the milling machine for 3 hours (4 hours permissible)
To determine exposure, compare actual time (C) to the permissible exposure time (T) for each noise level, then add the ratios:
Formula: Sum = C1/T1 + C2/T2 + C3/T3
At 90 dBA, OSHA allows 8 hours of exposure. → C1/T1 = 2/8
At 90 dBA, OSHA allows 8 hours of exposure. → C2/T2 = 2/8
At 95 dBA, OSHA allows 4 only hours of exposure. → C3/T3 = 3/4
Total = 2/8 + 2/8 + 3/4 = 10/8
Because the total (10/8) is greater than 1, the worker’s exposure exceeds the 90 dBA 8-hour TWA. Therefore, the worker is required to wear mandatory hearing protection.
Note: According to OSHA 1910.95, noise levels below 80 dBA are not included when calculating the 8-hour exposure level. Therefore, the worker's 1-hour 65 dBA exposure during the lunch break was excluded in the calculation.Reference: OSHA Technical Manual (OTM) Section III: Chapter 5 - Adding Noise Exposure Durations.
Knowledge Check Choose the best answer for the question.
5-4. The maximum legal permissible exposure limit (PEL) for noise is _____ for all workers during a 8-hour workday.
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