August 13, 2018

Mr. Michael Rice
Occupational Health Office
Robley Rex VA Medical Center
800 Zorn Avenue
Louisville, Kentucky 40206

Dear Mr. Rice:

Thank you for your letter to the Occupational Safety and Health Administration’s (OSHA) Directorate of Enforcement Programs. You requested a clarification of the provisions of OSHA’s Occupational Noise Exposure Standard, 29 CFR 1910.95 (Noise standard) regarding exposure to impulse or impact noise. 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 specific question is paraphrased below, followed by OSHA’s response.

Background: Impulsive noise, which includes impact and impulse noise, is a rapid rise in sound pressure that typically last less than one second. Impulsive noise is generally more hazardous than continuous noise, and it has a synergistic effect when combined with continuous noise exposure. Some exposures can have peak levels above 170 decibels or dB (e.g., flash-bangs, large caliber firearms, breaching operations).

Your letter references an OSHA letter of interpretation to Mr. David George, April 1, 1991, addressing impulse noise. You quote the section of that letter that states, “The OSHA limit for impulsive or impact noise is also 140 dB peak sound pressure level. This limit is independent of the duration of the noise impulse. There is no OSHA limit for number of exposures to impulsive or impact noise. Impulsive or impact noise must be integrated into the measurement of continuous noise exposure, however.”

Question: If the maximum impulsive or impact noise level of 140 dB is reached, e.g., where employees conduct annual weapons firing, must employees be entered into the hearing conservation program regardless of whether they meet or exceed the action level, i.e., an 8-hour time-weighted average sound level (TWA) of 85 decibels measured on the A scale, slow response (85 dBA)?

Response: No, a hearing conservation program is not required unless workers are exposed at or above the action level of 85 dBA, measured as an 8-hour time weighted average, as required by the Noise standard at 29 CFR 1910.95(c).

Paragraph 29 CFR 1910.95(d)(2)(i) goes on to require that all continuous, intermittent, and impulsive sound levels from 80 dB to 130 dB be integrated into the measurement of noise exposure. As discussed in the January 16, 1981, preamble to the final rule for the Noise standard, the range of 80 dB to 130 dB reflected the technological limitations of sound level meters and dosimeters at the time the Noise standard was issued. See, 46 Federal Register 4137. Please be advised even most of the existing commercially available dosimeters will not accurately integrate peak noise levels greater than the maximum range of the instrument, typically 130-140 dB.

For the noise exposures such as you describe, where employees conduct annual weapons firing, even if the measured 8-hr TWA does not reach the action level, OSHA encourages employers to administer a hearing conservation program, especially if hearing protection is the method used to control the noise exposure. Any employer may choose to include their workers (regardless of individual noise exposure levels) in a hearing conservation program, as long as all of the other provisions of the standard are followed for each employee (see OSHA’s letter of interpretation to Mr. Ben F. Ervin, January 19, 1982).

In addition, please keep in mind that Table G-16 of OSHA’s Noise standard at 29 CFR 1910.95 states, “Exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level.” Thus, exposure to noise above that level is not allowable. See also, OSHA’s letter of interpretation to Dr. Todd Sagin, December 7, 1987, regarding ear blasts from earphones. OSHA’s Noise standard at paragraph 29 CFR 1910.95(b)(1) states that when employees are subjected to sound exceeding those listed in Table G-16, feasible engineering and/or administrative controls must be used to reduce noise levels at their workplace. If engineering and administrative controls fail to reduce sound levels within the levels specified in Table G-16, personal protective equipment must be provided and used to reduce sound to permissible limits.

Current OSHA enforcement policy regarding 29 CFR 1910.95(b)(1) allows employers to rely on personal protective equipment and a hearing conservation program, rather than engineering and/or administrative controls, when hearing protectors will effectively attenuate the noise to which employees are exposed to acceptable levels. A properly administered hearing conservation program will provide training on hearing protectors and their selection, fitting, use, and care. (See Table G-16 of 29 CFR 1910.95 and Table G-16A of Appendix A to 29 CFR 1910.95). In situations such as weapons firing, where noise levels exceed 140 dB, single hearing protection may not be adequate.

See also the National Institute for Occupational Safety and Health (NIOSH) Health Hazard Evaluations (HHE), Measurement of Exposure to Impulsive Noise at Indoor and Outdoor Firing Ranges During Tactical Training Exercises, at www.cdc.gov/niosh/hhe/reports/pdfs/2013-0124-3208.pdf, and Noise and Lead Exposures at an Outdoor Firing Range- California, at www.cdc.gov/niosh/hhe/reports/pdfs/2011-0069-3140.pdf. These studies show peak sound level meter measurements greater than 160 dB during gunfire and recommend noise controls that include the use of noise suppressors on firearms, limiting the number of daily gunfire exposures, the use of double hearing protection, and a hearing conservation program that meets the requirements of the OSHA Noise standard.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA’s requirements are set by statute, standards, and regulations. Our 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 http://www.osha.gov. If you have further questions, please feel free to contact the Office of Health Enforcement at (202) 693-2190.

Sincerely,

Amanda Edens, Acting Director
Directorate of Enforcement Programs