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Standard Interpretations - Table of Contents
• Standard Number: 1910.95; 1910.95(h)(5); 1910.95(h)(5)(ii)

April 23, 2010

Mr. Travis McColley
7625 Golden Triangle Drive
Eden Prairie, MN 55344

Dear Mr. McColley:

Thank you for your letter to the Occupational Safety and Health Administration's (OSHA's) Chicago Regional Office. Your letter was forwarded to OSHA's Directorate of Enforcement Programs (DEP) for a response.  In your letter, you requested information about Appendix E to OSHA's standard at 29 CFR 1910.95, Occupational noise exposure, and the applicability of the updated American National Standards Institute's (ANSI's) use of an artificial ear International Organization of Standardization (ISO) 318 coupler.

This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any question not delineated within your original correspondence.  Your paraphrased scenario and question are presented below, followed by our reply.

Scenario:  OSHA's standard at 29 CFR 1910.95(h)(5) addresses audiometer calibration, and states:

(i) The functional operation of the audiometer shall be checked before each day's use by testing a person with known, stable hearing thresholds, and by listening to the audiometer's output to make sure that the output is free from distorted or unwanted sounds. Deviations of 10 decibels or greater require an acoustic calibration.

(ii) Audiometer calibration shall be checked acoustically at least annually in accordance with Appendix E: 'Acoustic Calibration of Audiometers.' Test frequencies below 500 Hz and above 6000 Hz may be omitted from this check.  Deviations of 15 decibels or greater require an exhaustive calibration.

(iii) An exhaustive calibration shall be performed at least every two years in accordance with sections 4.1.2; 4.1.3.;; 4.2; 4.4.1; 4.4.2; 4.4.3; and 4.5 of the American National Standard Specification for Audiometers, S3.6-1969.  Test frequencies below 500 Hz and above 6000 Hz may be omitted from this calibration.

ANSI S3.6-1969 was updated three times to ANSI S3.6-1989, ANSI S3.6-1996 and ANSI S3.6-2004.  As part of these updates, an artificial ear International Organization of Standardization (ISO) 318 coupler is used to obtain reference equivalent threshold sound pressure level (RETSPL) values.  Within the audiological community, the ISO 318 coupler has become more prominent due to the need for other measurements to be taken.

Question: Would OSHA allow the use of the ISO 318 coupler to be used for both acoustical and exhaustive calibrations using the ANSI S3.6-2004 RETSPLs for Telephonics Dynamic Headphone (TDH) type?

Reply:  Where an OSHA standard incorporates an earlier consensus standard, the only way the OSHA standard can be changed to adopt the new version is through rulemaking.  However, while requiring employers to comply with existing OSHA standards, the Occupational Safety and Health Act of 1970 (OSH Act) also authorizes OSHA to treat certain violations, which have no direct or indirect relationship to safety and health, as de minimis.  OSHA enforcement policy provides that a violation may be de minimis if an employer complies with an amendment of a consensus standard rather than with the OSHA standard, and the updated consensus standard is at least equally protective of employee safety and health.  OSHA does not issue citations for de minimis violations, penalties are not proposed, and abatement of the violation is not required by the employer.

OSHA considers the revised ANSI standard S3.6-2004 to be equally protective to ANSI S3.6-1969, and generally accepted good methods for audiometer calibrations.  ANSI S3.6-2004 states in paragraph 9.1.2 that supra-aural earphones shall be calibrated with an International Electrotechnical Commission (IEC) 60318-3 artificial ear or an NBS 9A coupler.  Therefore, if an employer chooses to use ANSI S3.6-2004 and meets all of the requirements, the employer will then be considered to be in de minimis violation of OSHA's 29 CFR 1910.95 requirements.

Section 1910.95(h)(5)(ii) states that should the calibrated levels deviate from those levels listed in Appendix E, Tables E-1 and E-2, an exhaustive calibration is required.  Therefore, if the ISO 318 coupler is equivalent to the IEC 60318-3, OSHA would consider its use for both acoustical and exhaustive calibrations using the RETSPLs provided in the ANSI standard to be a de minimis violation.  If another type of earphone is used, then the employer must either obtain a valid RETSPL from the manufacturer, or use the NBS 9A coupler.

Further, the State of Minnesota under an agreement with OSHA operates an occupational safety and health program in accordance with Section 18 of the Occupational Safety and Health Act of 1970.  The Minnesota Occupational Safety and Health program is administered by the Minnesota Department of Labor and Industry.  The department's Occupational Safety and Health (OSH) Division is responsible for compliance program administration, conducting enforcement inspections, adoption of standards, and operation of other related OSHA activities.  State plans are required to implement regulations that are "at least as effective" as the federal standards.  For specific Minnesota OSHA requirements and free consultation services, we recommend that you contact:

Minnesota Department of Labor and Industry, Minnesota OSHA
443 Lafayette Road North
St. Paul, Minnesota 55155-4307
PH: (651) 284-5050
TOLL FREE: (877) 470-6742
FAX: (651) 284-5741

Thank you for your interest in occupational safety and health.  We hope you find this information helpful.  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  If you have any further questions, please feel free to contact the Office of Health Enforcement at (202) 693-2190.


Thomas Galassi, Acting Director
Directorate of Enforcement Programs

Standard Interpretations - Table of Contents

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