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.

December 16, 2021

Dr. Tanya Rhodes
Custom Protection Ear
211 Poinciana Lane
Largo, Florida 33770

Dear Dr. Rhodes:

Thank you for your letter to the Occupational Safety and Health Administration (OSHA), Directorate of Enforcement Programs. You requested information on the requirements of OSHA’s Occupational Noise Exposure standard, 29 CFR § 1910.95. Specifically, you requested guidance on application of the Environmental Protection Agency’s (EPA) proposed noise reduction rating (subject fit) (NRR (SF)). This letter constitutes OSHA’s interpretation only of the requirements herein, and may not be applicable to any questions not delineated within your original correspondence. Your statement and specific questions are paraphrased below, followed by OSHA’s responses.


OSHA’s noise standard at paragraph 1910.95(j)(1) states employers must provide adequate hearing protection devices (HPDs) to employees based on the specific noise environments in which they will be used, and the product’s attenuation evaluated using a method described in the standard’s mandatory Appendix B, Methods for estimating the adequacy of hearing protection attenuation. Paragraph (j)(2) states that hearing protectors must attenuate employee exposure at least to an 8-hour time-weighted average of 90 decibels, and paragraph (j)(3) states that, for employees who have experienced a standard threshold shift (STS), hearing protectors must attenuate employee exposure to an 8-hour time-weighted average of 85 decibels or below.

One method in Appendix B specifies the EPA laboratory testing requirements for HPDs, as set forth at 40 CFR § 211 subpart B, Hearing Protective Devices.1 The EPA requires HPD manufacturers to include the NRR on the HPD packaging. The NRR describes the average sound level reduction (attenuation) provided by the HPD under laboratory test conditions regulated by the EPA (i.e., the higher the NRR, the greater the noise reduction).

As you know, the American National Standards Institute (ANSI) develops many industry standards that address occupational safety and health. One of their standards, issued jointly with the Acoustical Society of America (ASA), referenced in your letter, is ANSI/ASA S12.6-2008, Methods for Measuring the Real-Ear Attenuation of Hearing Protectors. This standard specifies laboratory-based procedures for measuring, analyzing, and reporting passive noise-reducing capabilities of HPDs. The procedures consist of psychophysical tests conducted on human subjects to determine real-ear attenuation measured at hearing threshold. Two fitting procedures are provided: Method A for trained-subject fit, and Method B for inexperienced-subject fit, intended to approximate protection that can be attained by two groups of users in workplace hearing conservation programs.

On August 5, 2009, EPA issued a proposed rule in the Federal Register, Product Noise Labeling Hearing Protection Devices, which would update 40 CFR § 211 to reflect changes in HPDs that have evolved since EPA issued the current regulation in 1979. See, 74 FR 39150. Among other things, under the proposed rule, EPA would adopt the ANSI S12.6-2008—Method-A testing protocol for all hearing protectors in their “passive” mode.2 Method A permits test subjects to be experienced with the use and fitting of protectors and as such, reflects the attenuation obtained by trained users. EPA noted that Method A subject-fit procedure is more appropriate to provide an accurate assessment of the acoustic performance.

Question 1: Will OSHA accept the use of the ANSI/ASA NRR (SF) rating for custom earplugs instead of the (NRR-7)/2 rating? If not, can OSHA provide a statement saying that custom earplugs are only subjected to the NRR-7 and not the (NRR-7)/2 de-rating?

Response: Appendix B to 29 CFR 1910.95 states, “The most convenient method is the Noise Reduction Rating (NRR) developed by the Environmental Protection Agency (EPA)” and describes methods of using the NRR to determine whether a particular hearing protector provides adequate protection within a given exposure environment. Under current enforcement policy, OSHA uses the unadjusted NRR to assess the adequacy of hearing protection when evaluating compliance with the hearing conservation program (HCP). However, in some circumstances, OSHA compliance personnel apply a safety factor of 50 percent to the laboratory-based NRR, above and beyond the 7 dB subtraction called for when using A-weighing measurements. OSHA uses this NRR-7/2 rating adjustment when considering whether an employer should implement engineering controls, but the safety factor adjustment is not used when evaluating the adequacy of HPDs under the HCP. For further information, please see OSHA’s Technical Manual’s noise chapter at: www.osha.gov/otm/section-3-health-hazards/chapter-5.

Please note that where an employer does not use a method included in Appendix B, a violation of paragraph 1910.95(j)(1) may exist. The ANSI/ASA NRR (SF) is not one of the methods listed in Appendix B when evaluating the attenuation of a HPD.

Question 2: Will OSHA accept a personal attenuation rating (PAR) instead of an NRR/NRR (SF) de-rating?

Response: As discussed above, the OSHA noise standard requires employers to use an NRR method described in Appendix B. An employer would be in violation of paragraph 1910.95(j)(i) if a method consistent with Appendix-B was not used. Please see OSHA’s October 20, 2017, letter of interpretation to Dr. Laurie Wells.3

Question 3: Will OSHA endorse the usage of PAR machines for compliance with the noise standard?

Response: OSHA does not endorse or approve such equipment or products.

Question 4: Could OSHA provide the document that confirms Method-B/NRR (SF) is acceptable for compliance with the hearing conservation program (HCP)?

Response: Please see the Response to Question 1 above.

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 assure 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


[1] Appendix B to 29 CFR 1910.95 also allows employers to evaluate the adequacy of HPD attenuation by using one of the methods developed by the National Institute for Occupational Safety and Health (NIOSH). See, List of Personal Hearing Protectors and Attenuation Data, HEW Publication No. 76-120, 1975, pages 21-37.

[2] EPA’s proposed rule was issued in 2009, but OSHA is not certain about the status of the rulemaking. See www.regulations.gov/document?D=EPA-HQ-OAR-2003-0024-0040. Since 2009, ANSI revised its S12.6-2008 to S12.6-2016, but this revised industry standard still includes Method A, designated trained-subject fit, and Method B, designated inexperienced-subject fit.

[3] See www.osha.gov/laws-regs/standardinterpretations/2017-10-20,