OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

October 12, 2021

Daniel J. Brustein, MD
2893 Berkshire Road
Cleveland Heights, OH 44118 

Dear Dr. Brustein:

Thank you for your letter to the Occupational Safety and Health Administration’s (OSHA) Directorate of Enforcement Programs. You requested clarification on OSHA’s Occupational Noise Exposure standards, 29 CFR § 1910.95 and 29 CFR § 1926.52. Specifically, you request that OSHA review its enforcement guidance concerning the adjustment of noise exposures as an 8-hour Time Weighted Average (TWA) and OSHA’s permissible exposure limit (PEL) for noise during extended workshifts. This letter constitutes OSHA’s interpretation only of the requirements discussed and may not be applicable to any questions not delineated within your original correspondence. Your paraphrased question and our response are below.

Background: In your letter, you ask OSHA to review its interpretation of the OSHA Noise standards and to withdraw any instructions or interpretations that restrict noise exposure measurements beyond 8 hours (extended work shifts) for compliance with the PEL, 90 dBA, as provided in its letter of interpretation to Mr. Jonathan A. Jacoby, March 26, 1982, the OSHA Policy Regarding PEL Adjustments for Extended Work Shifts, November 10, 1999, and Section III: Chapter 5 of the OSHA Technical Manual (OTM) on Noise. You indicate that these guidance documents misinterpret the spirit of the noise standards at 29 CFR § 1910.95 and 29 CFR § 1926.52, and Tables G-16 and D-2, respectively located within each standard.

Question: Why does OSHA instruct its compliance officers to “adjust” the noise action level (AL) but not the permissible exposure limit when sampling for noise during extended work shifts?

Response: As you note in your letter, during an extended work shift (i.e. greater than 8 hours) the PEL found in 29 CFR § 1910.95 (a) and (b)(1), Table G-16, and 29 CFR § 1926.52, Table D-2, is not adjusted and sampling is limited to the highest 8-hour noise exposure of a 40-hour work shift. These tables (G-16 and D-2) only allow for exposures of 8 hours or less.

OSHA’s 90 dBA PEL for noise has been in effect since 1971 and the Agency has no immediate plans to revise it. Any revision to the PEL would require the Agency to conduct notice and comment rulemaking. Although OSHA conducted rulemaking in 1981 to establish new provisions for the hearing conservation requirements in the general industry noise standard, this only resulted in a revision to section 1910.95(b)(3) of the standard, and no changes were made to requirements pertaining to the 90 dBA PEL. Thus, the 8-hour TWA for compliance with the PEL was not adjusted and continues to remain unadjusted for extended work shifts.1 Although Table G-16 and Table D-2 do not explicitly state that measurements over 8 hours should be excluded in noise exposure calculations for compliance with the PEL, additional legal limits for the PEL for an extended work shift cannot be assumed even when such calculations are possible.

The limits expressed in Tables G-16 and D-2 are based on well-established studies of the relationship between prolonged noise exposures and dose-response which show that the effects of noise as a function of both level and duration can permanently impair one’s hearing.2 As a reminder, when employees are exposed to noise beyond an 8-hour work shift, OSHA compliance officers are instructed to either sample the worst continuous 8-hour work period of the entire extended work shift, or to collect multiple samples over the entire work shift. When the latter approach is used, the PEL is calculated based upon the worst 8 hours of exposure during the entire work shift. Exposure calculations from either method can be compared to the PELs in Tables G-16 and D-2.

It should be noted that OSHA standards set minimum requirements to ensure that workers are protected from safety and health workplace hazards, and employers should follow the most protective guidance when feasible.3, 4 These tables, along with OSHA’s instructions and letters of interpretations referenced in your letter, provide useful guidance for making workplace noise exposure measurements and assessing compliance with OSHA’s noise standards. It is therefore not necessary to withdraw them at this time.

Thank you for your interest in occupational safety and health. I hope you find this information helpful. OSHA’s requirements are set by statute, standards, and regulations. Letters of interpretation do not create new or additional requirements but rather explain these requirements and how they apply to particular circumstances. This letter constitutes OSHA’s interpretation of the requirements discussed. From time to time, letters are affected when the agency updates a standard, a legal decision impacts a standard, or changes in technology affect the interpretation. To ensure that you are using the correct information and guidance, please consult OSHA’s website at www.osha.gov. If you have further questions, please feel free to contact the Office of Health Enforcement at (202) 693-2190.


Kimberly Stille, Acting Director
Directorate of Enforcement Programs


1OSHA Preamble, Occupational Noise Exposure; Hearing. Conservation Amendment, Federal Register, Volume 46, No. 11, January 16, 1981, pgs. 4078-4085.


2OSHA Preamble, Occupational Noise Exposure; Hearing Conservation Amendment, Federal Register, Volume 46, No. 11, January 16, 1981, p. 4081.

3See, NIOSH Criteria for a Recommended Standard Occupational Noise Exposure, Revised Criteria 1998.

4See, ACGIH Threshold Limit Values (TLVs), Audible Sound, 2018.