After a Confirmed STS: The Follow-Up Actions OSHA Requires

A confirmed standard threshold shift (STS) is not the end of the paperwork, it is the start of it. Under 29 CFR 1910.95(g)(8), once an employer determines that an employee's annual audiogram shows an STS, three separate actions come due, each with its own trigger and deadline. Miss one and the hearing conservation program has a compliance gap even if the audiometric testing itself was done correctly. This is the step employers most often get wrong, not because the rule is unclear, but because the three actions live in different parts of the program and nobody owns all three.

What exactly triggers the follow-up requirements?

The trigger is a confirmed STS, not the first test that flags one. OSHA's standard threshold shift is an average shift of 10 dB or more at 2000, 3000, and 4000 Hz in either ear, compared to that employee's baseline audiogram. When the annual test shows an STS, the employer may retest within 30 days and treat that retest as the annual audiogram of record. If the shift holds on retest, or the employer chooses not to retest, the shift is confirmed and the follow-up clock starts. A physician or other suitably trained professional can also determine that a confirmed shift is not work-related, which removes the obligation to treat it as an STS for program purposes, though it may still be evaluated for OSHA 300 log recordability under 29 CFR 1904.10 on a separate track.

What does the written notification require?

The employer must notify the affected employee in writing within 21 days of determining that the STS occurred. This is not a verbal heads-up at the testing van door, it has to be a written record, and the clock runs from the determination date, not from the original test date. On a mobile hearing testing program where results come back from a reviewing audiologist days or weeks after the visit, the 21-day window starts when that determination lands, which means an employer tracking this manually across a spreadsheet and an inbox is exactly the scenario this requirement is built to catch out. A written notice that goes out late is a documentation gap an inspector can find on file review alone, without ever talking to an employee.

What has to happen with hearing protection after an STS?

An employee who was not already using hearing protectors has to be fitted with them, trained in their use and care, and required to use them going forward. An employee who was already wearing protectors has to be refitted and retrained, and if the existing protector does not provide adequate attenuation for that employee's noise exposure, issued protectors with a greater attenuation rating. Employees get to choose among the suitable protectors an employer makes available, which means "refitting" is a conversation about options, not a one-size reissue. This step is where the hearing conservation program crosses over into the respiratory and PPE side of the operation, and it is the step most likely to get skipped when the audiogram review and the PPE program are handled by different people.

When is a referral for further evaluation required?

If the employer suspects that a medical pathology unrelated to hearing protector use is responsible for the shift, or if a problem is suspected that the audiometric test alone cannot resolve, the employee must be referred for a clinical audiological evaluation or an otological examination, as appropriate. This referral is not automatic for every confirmed STS. It depends on whether the reviewing professional sees something in the pattern of loss, the employee's symptoms, or the audiogram shape that points to a cause other than ordinary noise-induced shift. A reviewing audiologist who has the employee's full test history, not just the two audiograms being compared, is in the best position to make that call, which is one reason continuity of records across testing years matters as much as the test itself.

Follow-up action	Deadline / trigger	Who it falls on
Written notice to employee	Within 21 days of determining the STS	Employer
Fit/refit hearing protectors, retrain	Promptly after confirmation	Employer, PPE program
Referral for clinical evaluation	When pathology or unresolved cause is suspected	Employer, on reviewing professional's input
OSHA 300 log entry	Separate 1904.10 recordability test	Recordkeeping, not automatic

How does a revised baseline fit into this?

A confirmed STS does not automatically replace the employee's baseline audiogram. OSHA allows the employer to substitute the annual audiogram for the baseline when the STS is persistent, meaning it holds up on confirmation retest and the reviewing professional judges that the employee's hearing has genuinely changed rather than reflecting a temporary noise-related effect. Revising the baseline resets the reference point for measuring future shifts, which matters because carrying forward an outdated baseline can either mask a real ongoing decline or keep flagging the same shift as new every year. This decision belongs with the reviewing professional, not with whoever is entering results into the tracking spreadsheet.

How does Foster handle the follow-up clock on a mobile testing day?

Foster's audiometric software flags a three-frequency STS automatically at the point of testing, but the harder problem is what happens after the van leaves an on-site testing visit. See how the STS calculation itself works for the math behind the flag. The 21-day notification window, the protector refit, and any referral decision all depend on dates that start running once a result is determined, often after a reviewing audiologist has looked at the case, not on the day of the test. Foster's Compliance Workspace tracks each of those dates against the employee's record so a confirmed STS doesn't sit in an inbox past the notification deadline, and keeps the evidence (notice sent, protector reissued, referral made) attached to that employee's file for the next audit rather than scattered across email threads and paper sign-off sheets. For how a confirmed shift separately becomes an OSHA 300 log entry, see when an STS is recordable.

Frequently Asked Questions

Does every STS require a hearing protector refit?

Yes. Once an STS is confirmed, the employer must fit protectors (if the employee wasn't already using them) or refit and retrain (if they were), and provide greater-attenuation protectors if the current ones are inadequate for that employee's exposure.

Does a confirmed STS automatically mean a recordable OSHA 300 log case?

No. Recordability under 29 CFR 1904.10 is a separate test, based on whether the employee's total hearing level is 25 dB or more above audiometric zero at 2000, 3000, and 4000 Hz in the same ear, after age correction. A confirmed STS can be non-recordable, and a recordable case still requires the full set of 1910.95(g)(8) follow-up actions.

Who decides whether the shift was work-related?

A physician or other suitably trained professional makes that determination, not the employer. If they determine the STS is not work-related or not aggravated by occupational noise exposure, the mandatory follow-up actions under (g)(8) don't apply, though separate recordkeeping rules may still come into play.

Can the 21-day notification deadline be missed if the employee is on leave?

The rule doesn't carve out an exception for employee leave. The determination date starts the clock regardless of the employee's schedule, so employers need a way to deliver written notice even when the employee isn't on site, such as mail to the address on file.

Sources

• OSHA 29 CFR 1910.95, Occupational Noise Exposure
• OSHA 29 CFR 1904.10, Recording Criteria for Cases Involving Occupational Hearing Loss