OSHA 29 CFR 1910.95(g)(8) requires employers to notify workers in writing within 21 days of determining that a Standard Threshold Shift has occurred. This 21-day clock is one of the most commonly missed compliance timelines in hearing conservation programs — and failure to notify is an independent citation basis separate from any failure in the underlying STS determination. According to CDC/NIOSH, approximately 22 million U.S. workers face hazardous noise annually, with a significant fraction experiencing threshold shifts that trigger this notification requirement each year.
The 21-Day Clock and When It Starts
The 21-day notification window begins when the STS is “determined” — meaning when the professional supervisor reviews the audiogram and confirms the STS. The determination date is the reference point, not the date the audiogram was conducted. If the audiogram was conducted on January 1 but not reviewed by the professional supervisor until January 15, the 21-day clock starts January 15 and notification must be delivered by February 5.
This sequence has practical implications: delays in professional supervisor review extend the gap between audiogram and notification. Programs that batch audiograms for monthly professional supervisor review create notification risk if a worker’s audiogram sits in queue for several weeks before review.
OSHA 1910.95(g)(7)(ii) permits a retest within 30 days. However, the 21-day notification clock for confirmed STSs is not paused while awaiting a retest. If an STS is confirmed on the original test and the retest window is used, employers who wait for the retest result before notifying may violate the 21-day requirement. Best practice: if you intend to retest, conduct the retest before the 21-day clock expires, or notify the worker of the provisional STS determination pending retest.
Documentation of STS Notifications
Maintain documentation of each STS notification in the HCP records:
- Copy of the written notification provided to the worker
- Date notification was provided (must be within 21 days of STS determination)
- Confirmation of delivery (signature, certified mail receipt, or other documentation)
- Professional supervisor’s STS determination date (from which the 21-day clock started)
- Documentation of any follow-up actions taken (HPD refit, training, referral)
The 21-day notification is not the end of the STS response process — it is the first required step. The notification should trigger the follow-up actions: HPD refitting or replacement, additional training, and professional supervisor’s determination of whether medical referral is warranted. Document each follow-up action with the date completed. This complete documentation trail shows the employer followed through on all required STS response steps.
Frequently Asked Questions
STS Determinations, Notifications, and Follow-Up — All Documented
Soundtrace Professional Supervisor review triggers the 21-day STS notification workflow automatically, generating the documentation trail for OSHA compliance and WC defense.
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