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.

June 25, 1986

Mr. Darrell K. Mattheis
National Place, Suite 911
1331 Pennsylvania Avenue, N.W.
Washington, D.C. 20004

Dear Mr. Mattheis:

This is in response to your letter of October 7, asking for clarification of the time period given in the Hearing Conservation Amendment for notifying employees of a standard threshold shift (STS) in their hearing ability. Please accept my apology for the delay in response.

Employees must be notified of their STS within 21 calendar days from the date that the determination is made that their audiometric test showed the STS.

If we may be of future assistance, please feel free to contact us again.


John B. Miles, Jr.,
Directorate of Field Operations

October 7, 1985

Mr. John B. Miles
Director of the Directorate of
Field Operations
U.S. Department of Labor - OSHA
Room N-3603
Washington, D.C. 20210

Dear John:

Recently I have received a number of questions concerning OSHA's Hearing Conservation Amendment. Some organizations are concerned about OSHA's interpretation of the time period allowed after an audiometric test, before an employee must be notified of the existence of a Standard Threshold Shift (STS).

The standard says that: "If a comparison of the annual audiogram to the baseline audiogram indicates a standard threshold shift as defined in paragraph (g)(10) of this section has occurred, the employee shall be informed of this fact in writing, within 21 days of the determination."

The questioners want to know whether the 21 day period begins the day the audiogram was taken? 21 days from the time the company receives the results of the test from the testing service? Or 21 days from the time the company makes its determination that a STS has occurred, (after having received test results)? Finally, are the 21 days, working of calendar days?

Any assistance that you can give me on these questions will be appreciated!


Darrell K. Mattheis