OSHA Recordkeeping: When an STS Becomes a 300 Log Entry

When does a standard threshold shift become an OSHA 300 Log entry?

A standard threshold shift (STS) under 1910.95 and a recordable hearing loss case under 29 CFR 1904.10 are two different determinations, and mixing them up is one of the most common recordkeeping errors in hearing conservation programs. Every STS — a 10 dB or greater average shift at 2000, 3000, and 4000 Hz in either ear compared to baseline — triggers the follow-up actions required by 1910.95 (notification, retest option, protector fitting). But it only becomes an OSHA 300 Log entry if it also meets the separate recordability test in 1904.10: the employee's total hearing level in the same ear must be 25 dB or more above audiometric zero, averaged at those same three frequencies. An STS that doesn't cross that 25 dB threshold gets handled under 1910.95 but doesn't go on the log.

How is an STS calculated for recordkeeping purposes?

The comparison starts with the employee's most recent audiogram against their baseline, averaged at 2000, 3000, and 4000 Hz in each ear separately — a shift in one ear only still counts. If age correction is applied (optional, at the employer's discretion, using tables in 1910.95 Appendix F), it adjusts the comparison for expected age-related hearing decline before determining whether a 10 dB shift actually occurred. The recordability check under 1904.10 then applies a second, independent test to that same ear's current hearing level: is it 25 dB or worse averaged across those frequencies, using the current audiogram values. Both tests use the same three frequencies, which is why documentation needs to track per-ear, per-frequency values rather than just a summary pass/fail.

Can age correction change whether an STS is recordable?

Yes, and this is where employers get tripped up. Age correction is optional for the STS determination under 1910.95 — an employer can choose to apply it or not — but 1904.10 explicitly allows age correction to be used for the recordability determination as well, using the same tables. If applying age correction moves the calculated shift below 10 dB, there's no STS and nothing to record. If an STS still exists after age correction but the age-corrected hearing level doesn't reach 25 dB, the case isn't recordable even though the STS itself still requires the 1910.95 follow-up steps. Employers need to decide up front, as a matter of program policy, whether they apply age correction consistently — switching approaches case by case invites scrutiny.

Determination	Governing section	Threshold
Standard threshold shift (STS)	29 CFR 1910.95	10 dB average shift at 2000/3000/4000 Hz vs. baseline, either ear
Recordable hearing loss case	29 CFR 1904.10	STS present, AND current level 25 dB+ above audiometric zero at same frequencies, same ear

What recordkeeping deadlines apply after a recordable STS?

Once an employer determines a case meets the 1904.10 recordability criteria, it goes on the OSHA 300 Log within the same recording timeframe that applies to other recordable injuries and illnesses — entered within 7 calendar days of the employer determining the case is recordable, not 7 days from the test date itself. If a later retest shows the shift is no longer present — the employee's hearing improved or the original result was affected by a temporary factor — 1904.10 allows the employer to erase or line out the original entry rather than leave a permanent record of a shift that didn't hold up.

How does Foster flag a possible STS during testing?

Foster's technicians compare each annual audiogram to the employee's stored baseline on-site, at 2000, 3000, and 4000 Hz per ear, the day of the test rather than in a batch review weeks later. When the average shift hits 10 dB or more in either ear, the tech flags the file for professional review before the visit ends, and separately calculates whether the current hearing level also crosses the 25 dB recordability threshold in that ear so the employer knows immediately whether they're looking at a 1910.95 follow-up only or a 1904.10 recordability question as well. That same-day flag is what lets an employer start the 21-day written notification clock and line up a retest or professional review without losing time to data-entry lag.

What do employers get wrong when logging STS cases?

The most frequent error is recording every STS on the 300 Log regardless of whether it clears the separate 25 dB threshold, which overstates the log and can itself draw scrutiny for inconsistent recordkeeping practice. The second is applying age correction inconsistently — using it for some employees' STS determinations and not others without a documented, uniform policy, which looks like the tables are being used to manage outcomes rather than measure hearing loss. The third is missing the 7-calendar-day recording window once a case is determined recordable, usually because the recordability determination itself got delayed behind an audiologist review that took longer than expected — the clock starts at the employer's determination, so tracking when that determination is actually made matters as much as the medical review itself.

Frequently Asked Questions

Does every STS require a 300 Log entry?

No — only STS cases that also meet the separate 25 dB recordability threshold in 1904.10 go on the log; others still require the 1910.95 follow-up steps but aren't recordable.

Who determines whether age correction applies?

The employer decides whether to apply age correction, using the tables in 1910.95 Appendix F, for both the STS and recordability determinations.

Can a recorded STS case be removed from the 300 Log later?

Yes, if a retest shows the shift is no longer present, the employer may line out or erase the earlier entry per 1904.10.

Foster Special Instruments supports hearing conservation program management including STS determination and recordkeeping support, backed by properly calibrated audiometers. See the full baseline audiogram rules that every STS comparison depends on.