The 21-day STS notification letter is one of the most frequently missed compliance requirements in hearing conservation programs. When a Standard Threshold Shift is confirmed by the professional supervisor, OSHA 29 CFR 1910.95(g)(8) requires written notification to the affected worker within 21 days. The letter must be in writing; verbal notification is insufficient. According to CDC/NIOSH, many employers with otherwise compliant HCPs miss the written notification requirement because they have no systematic process to generate notifications when STS determinations are made.
What the Notification Must Accomplish
OSHA does not provide a form notification letter, but the notification must inform the worker that an STS has occurred. Best practice content for the letter:
- Worker’s name and employee ID
- Dates of the baseline and annual audiograms being compared
- STS magnitude and which ear was affected
- Brief, plain-language explanation of what an STS means
- What follow-up actions are being taken (HPD refit, additional training, referral if warranted)
- Contact information for the EHS professional or professional supervisor with questions
The clock starts when the professional supervisor determines the STS — not when the audiogram was conducted. If audiograms are batched for monthly professional supervisor review, a worker tested on the 1st whose audiogram isn’t reviewed until the 28th has only 21 days from the 28th. Batch-review programs that delay PS review by weeks create systemic notification risk. Programs with faster PS review turnaround reduce this risk.
Delivery and Documentation
Deliver the notification in a way that creates documentation of both the content and the date. Options:
- Certified mail with return receipt (creates date-stamped proof of mailing and delivery)
- Electronic delivery with read receipt (timestamp records delivery)
- Hand delivery with worker signature and date
- Secure employer portal with documented notification timestamp
Maintain a copy of each STS notification letter in the worker’s HCP file, along with documentation of the delivery date and method. In OSHA inspections, the inspector may request to see notification letters for any STSs identified during the inspection period. Without retained copies, the employer cannot demonstrate that the 21-day requirement was met.
Frequently Asked Questions
STS Notifications Generated and Documented Automatically
Soundtrace Professional Supervisor review triggers the STS notification workflow — generating compliant written notifications with documentation of timing and delivery for every confirmed STS.
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