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 10, 1986

P.W. Hess, Ph.D.
Director, Environmental Affairs
Hershey Foods Corporation
Technical Center
Post Office Box 805
Hershey, Pennsylvania 17033

Dear Dr. Hess:

This is in response to your letter of July 31, to Mr. John B. Miles, Director, Directorate of Field Operations, Occupational Safety and Health Administration (OSHA), asking: "How do I calibrate the Type II dosimeter in the field to be positive that it is accurately integrating the impulse noise, as mandated by the Hearing Conservation Amendment?" Your letter was forwarded to this office for response.

OSHA does not specify exactly how monitoring instruments should be calibrated. Paragraph 29 CFR 1910.95(d)(2)(ii) of the OSHA Hearing Conservation Amendment states that: "Instruments used to measure employee noise exposure shall be calibrated to ensure measurement accuracy."

In your letter you also raised a question regarding what method OSHA uses to calibrate its noise dosimeters. Please note on page I-14 of OSHA Instruction CPL 2.20A., March 30, 1984, the Industrial Hygiene Technical Manual, that OSHA requires its compliance officers to "follow the manufacturer's instructions" for the calibration of duPont MK-1, GenRed, and Quest noise dosimeters. This dictum applies also to the duPont MK-2 and and Metrosonics dosimeters used by OSHA personnel. In addition to field calibrations, all OSHA noise measurement Instruments are returned yearly to the OSHA Measurement and Calibration Laboratory in Cincinnati, Ohio for checkup and calibration.

If you have questions about the calibration of your noise monitoring instruments, we recommend that you consult with the instrument manufacturer(s) for assistance. If you need additional information regarding the OSHA calibration procedures, please contact Mr. Raymond G. Kunicki of my staff at (202) 523-7065.


Edward J. Baier
Directorate of Technical Support