OSHA Recordkeeping·300 Log·12 min read·Updated March 2026
The OSHA 300 Log is one of the most commonly mismanaged elements of an occupational hearing conservation program — not because employers aren’t paying attention, but because the recordkeeping rule for hearing loss (29 CFR 1904.10) uses different thresholds, different reference points, and different logic than the audiometric surveillance standard (29 CFR 1910.95). An employer can run a fully compliant hearing conservation program under 1910.95 and still be out of compliance with 1904.10, because the two standards are asking different questions from the same audiometric data. This guide explains exactly how the 300 Log recordability determination works for hearing loss, where employers consistently get it wrong, how age correction applies, and what happens when a recorded entry needs to be revised.
Soundtrace provides audiometric reports with 300 Log recordability determinations pre-calculated by the reviewing PLHCP, so the recordkeeping decision is never ambiguous.
The Core Confusion in One SentenceThe STS (Standard Threshold Shift under 1910.95) is a shift from baseline measured in dB. The 300 Log threshold (under 1904.10) is a total hearing level measured from audiometric zero. A worker can have an STS without being recordable, and — theoretically — be recordable without an STS triggering the standard 1910.95 response sequence.
Two Standards, Two Different Questions
OSHA’s hearing loss rules operate under two separate regulatory frameworks that are related but legally distinct:
- 29 CFR 1910.95 (Occupational Noise Exposure) governs the hearing conservation program: noise exposure monitoring, audiometric testing, HPD provision, training, and the STS response sequence. Its purpose is worker protection and early detection of progressive hearing loss.
- 29 CFR 1904.10 (Recording Criteria for Cases Involving Occupational Hearing Loss) governs 300 Log recordkeeping for hearing loss. Its purpose is workforce-level tracking of occupational hearing disease for OSHA statistical and inspection purposes.
These two standards use different metrics, different reference points, and different threshold values. An audiometric result that triggers an STS response under 1910.95 may or may not generate a recordable case under 1904.10. The determination must be made separately for each framework.
Figure 1 — 1910.95 vs. 1904.10: Two Different Standards, Two Different Determinations
Same audiometric data, different questions. Both determinations must be made independently for every audiogram showing a threshold shift.
Element
1910.95 — STS (HCP)
1904.10 — 300 Log Recordability
Question asked
Has the worker’s hearing shifted from their baseline?
Has the worker’s hearing reached a total level that is recordable?
Trigger metric
10 dB average shift at 2k/3k/4k Hz from baseline
STS + total hearing level ≥ 25 dB HL from audiometric zero
Reference point
Worker’s own baseline audiogram
Audiometric zero (0 dB HL)
Age correction
Permitted (Appendix F of 1904.10)
Permitted (same Appendix F)
Consequence
Notification, HPD refit, retraining, physician referral
Entry on OSHA 300 Log as occupational illness
Triggered independently?
Yes — STS ≠ recordable case
Yes — recordable ≠ STS required
STS vs. Recordability: Why They’re Not the Same
The most common employer misconception is that every OSHA STS automatically requires a 300 Log entry. This is incorrect. The two tests can produce divergent results in both directions:
- STS without recordability: A worker with excellent pre-employment hearing (baseline at 5 dB HL average) develops a 12 dB average shift, reaching an annual audiogram average of 17 dB HL. This is a confirmed STS requiring the full 1910.95 response sequence. It is not a recordable case under 1904.10 because the resulting total hearing level (17 dB) is below the 25 dB recordability threshold.
- Recordable without a new STS: A worker whose baseline was revised upward after a prior confirmed STS now has a high baseline audiogram. A subsequent annual audiogram shows a small additional shift that, combined with the already-elevated total hearing level, puts the total average above 25 dB HL. Even if this new shift does not reach the 10 dB STS threshold from the revised baseline, the total level may be recordable.
The Most Common MistakeMany employers record every STS on the 300 Log and stop checking. Others record nothing until an inspector asks. Both approaches are wrong. The 300 Log determination must be made every time an STS occurs, by checking whether the annual audiogram’s average hearing level at 2000/3000/4000 Hz in the affected ear meets or exceeds 25 dB HL from audiometric zero — separately from the baseline comparison.
The 25 dB Recordability Threshold: What It Measures and From Where
The recordability threshold under 1904.10 is 25 dB HL, averaged at 2000, 3000, and 4000 Hz, measured from audiometric zero. This is a straightforward comparison between the annual audiogram values and 25 dB HL. It does not matter what the baseline was. It does not matter when the worker was hired. The only question is: does the average of the three frequency thresholds in the affected ear on the most recent audiogram equal or exceed 25 dB HL?
Audiometric zero (0 dB HL) is the reference standard for normal hearing in young adults with no occupational noise exposure. It is defined by ANSI S3.6. All pure-tone audiometric test results are reported relative to this standard — a threshold of 20 dB HL means the worker needs sound to be 20 dB louder than audiometric zero to hear it at that frequency.
The 25 dB HL threshold was selected by OSHA as the level at which hearing loss begins to have meaningful functional impact on speech communication. Workers below this threshold are in the normal-to-mild hearing range. Workers at or above it are considered to have a hearing level that warrants recording as an occupational illness.
Figure 2 — The 25 dB Recordability Threshold: What It Is and What It Isn’t
The 25 dB threshold is measured from audiometric zero (0 dB HL) — not from the worker’s baseline. It applies to the current annual audiogram result, not to the shift itself.
✗ Common Misconception
“The STS is 10 dB, so the recordability threshold is 10 dB from baseline.”
“Every STS = 300 Log entry.”
“The 25 dB threshold is measured from the worker’s baseline.”
✓ Correct Application
Recordability requires two conditions: (1) an STS has occurred AND (2) the resulting total hearing level is ≥ 25 dB HL from audiometric zero.
The 25 dB threshold is compared to the annual audiogram result, not the shift amount. A worker starting at 20 dB HL baseline who shifts 10 dB reaches 30 dB HL → recordable. A worker starting at 5 dB HL who shifts 12 dB reaches 17 dB HL → not recordable.
Worked Example: Four Workers, Four Different Outcomes
Figure 3 — Recording Decision: Four Workers, Four Audiometric Scenarios
Same noise exposure, different starting points and results. Illustrates why baseline history determines recordability even when shifts are identical.
Worker
Baseline avg (2/3/4k)
Annual avg (2/3/4k)
Shift from baseline
STS? (1910.95)
Total ≥ 25 dB HL?
Recordable? (1904.10)
A
5 dB HL
17 dB HL
+12 dB
Yes ✓
No (17 < 25)
No — STS but not recordable
B
15 dB HL
28 dB HL
+13 dB
Yes ✓
Yes (28 ≥ 25)
Yes — both conditions met ⚠
C
20 dB HL
27 dB HL
+7 dB
No (7 < 10)
Yes (27 ≥ 25)
No — no STS; total level irrelevant
D
22 dB HL
33 dB HL
+11 dB
Yes ✓
Yes (33 ≥ 25)
Yes — both conditions met ⚠
Worker C illustrates a critical edge case: total hearing level exceeds 25 dB HL but no STS occurred. The 300 Log entry is not triggered because both conditions (STS + total level ≥ 25) must be met simultaneously. Worker A has an STS but is not recordable because the resulting total level is only 17 dB HL.
Age Correction: Permitted But Not Required
OSHA permits employers to use age correction when calculating whether an STS has occurred for 300 Log recordability purposes. Appendix F of 29 CFR 1904.10 provides age-correction tables for male and female workers at each test frequency. Age correction subtracts the expected age-related threshold change from the measured annual audiogram before comparing to baseline, thereby isolating the portion of the shift attributable to occupational noise rather than presbycusis.
Age correction is optional — employers may choose not to apply it. When applied, it can only reduce or eliminate the apparent STS. It cannot increase the measured shift. The practical effect is that some STS cases that would otherwise be recordable are not recorded when age correction is applied and the age-corrected shift falls below 10 dB.
Age Correction: Two Separate DecisionsOSHA’s 1910.95 and 1904.10 standards each independently permit age correction. An employer can choose to apply age correction under 1904.10 (recordkeeping) without applying it under 1910.95 (STS notification), or vice versa. These are separate program decisions. Most programs apply age correction consistently across both, but the standards do not require this.
Figure 4 — Age Correction Worked Example: How It Changes the Recording Decision
Same worker, same audiometric data. Age correction reduces the apparent shift and may eliminate recordability. Values are illustrative; actual age correction values come from Appendix F tables.
Step
Without Age Correction
With Age Correction
Worker profile
Male, age 58 at baseline, age 63 at annual. Baseline avg 18 dB HL; Annual avg 30 dB HL.
Raw shift
30 − 18 = +12 dB
Same raw shift: +12 dB
Age correction value
Not applied
Appendix F value for male, age 58→63: −4.5 dB (example)
Age-corrected shift
+12 dB (unadjusted)
12 − 4.5 = +7.5 dB
STS? (≥ 10 dB)
Yes (12 ≥ 10)
No (7.5 < 10)
Total level ≥ 25?
Yes (30 dB HL)
Same annual result: 30 dB HL
Recordable?
Yes — record on 300 Log
No — age correction eliminates STS; no entry required
Age correction does not change the annual audiogram result (still 30 dB HL). It changes whether an STS is considered to have occurred by attributing part of the shift to aging rather than noise exposure. The decision to apply age correction must be made before examining results and applied consistently across the workforce.
Even when both conditions are met (STS confirmed and total level ≥ 25 dB HL), the case is only recordable if the hearing loss is work-related. Under 29 CFR 1904.5, a case is work-related if a work event or exposure either caused or significantly contributed to the condition. For hearing loss cases, OSHA presumes work-relatedness when the worker has occupational noise exposure — the burden of demonstrating non-work-relatedness falls on the employer, not OSHA.
The PLHCP reviewing the audiogram is responsible for providing a work-relatedness opinion when the recordability threshold is met. A bare “non-work-related” notation without clinical reasoning is insufficient documentation. The PLHCP’s determination must be supported by the clinical basis for attributing the loss to non-occupational causes, and the employer must retain this documentation.
Figure 5 — 300 Log Recording Decision Flowchart
Three sequential questions determine whether an audiometric result requires a 300 Log entry. All three must be answered “yes” for the case to be recordable.
STEP 1: Has an STS occurred?
Average the annual audiogram at 2000/3000/4000 Hz for the affected ear. Compare to baseline. Is the difference ≥ 10 dB? (Apply age correction if your program uses it.)
If NO → STOP. Case is not recordable. No 300 Log entry required.
If YES → Proceed to Step 2.
STEP 2: Is total hearing level ≥ 25 dB HL from audiometric zero?
Average the annual audiogram thresholds at 2000/3000/4000 Hz for the affected ear. Is this average ≥ 25 dB HL?
If NO → STOP. Case is not recordable. No 300 Log entry required.
If YES → Proceed to Step 3.
STEP 3: Is the hearing loss work-related?
Did the PLHCP determine the hearing loss is work-related? If the worker has occupational noise exposure, work-relatedness is presumed unless documented otherwise.
If NO → STOP. Case is not recordable. Document PLHCP non-work-related determination.
If YES → RECORD on OSHA 300 Log as occupational illness (Column M3). Notify employee if 1910.95 STS obligations have not already done so.
How to Record on the 300 Log
When all three conditions are met (STS + total level ≥ 25 dB HL + work-related), the case is entered on the OSHA 300 Log as follows:
- Column classification: Hearing loss is an illness, not an injury, under 1904.10. It is entered in Column M(3) (Hearing Loss) on the OSHA 300 Log — not in the injury columns.
- Case description: The case description should identify the work area or job classification where the noise exposure occurred.
- Date: The date of the recordable event is the date the recording criteria were first met — typically the date of the audiometric test that produced the qualifying result, or the date the PLHCP confirmed the STS and work-relatedness.
- Days away / restricted: Occupational hearing loss from gradual noise exposure typically does not result in days away from work or work restrictions. Column G (days away) and Column H (restricted/transferred) are typically zero. However, if the PLHCP recommends temporary noise restriction while a case is under evaluation, restricted days should be recorded.
Figure 6 — OSHA 300 Log: Where Hearing Loss Cases Are Recorded
Hearing loss uses a specific column on the 300 Log. Misclassifying it as an injury instead of an illness is a common error that affects 300A summary accuracy.
300 Log Column
Label
Hearing Loss Entry?
Notes
Column G
Days away from work
Typically 0
Hearing loss rarely results in lost work time
Column H
Restricted work / transfer
Typically 0
Record if PLHCP recommends noise restriction
Column M(3)
Hearing loss
Check this box
Illness category for occupational hearing loss
Column J (injuries)
All other injuries
Do NOT use
Hearing loss is illness, not injury
When and How to Remove a 300 Log Entry
OSHA permits employers to line out (remove) a recorded hearing loss case from the 300 Log if, on the next audiogram, the threshold shift has resolved and the hearing level no longer meets the recordability criteria. Specifically, if the annual audiogram following the recorded case shows that the total hearing level at 2000/3000/4000 Hz has fallen below 25 dB HL, the prior entry may be removed.
However, the lined-out entry must be retained in the records. The original entry is not erased — it is struck through with a single line and a note explaining why it was removed. For the 300A annual summary, the entry is counted in the year it was originally recorded, regardless of when it was removed. The 300A for the year of removal does not include the case.
Removal Timing RulesA hearing loss entry can only be removed based on the next scheduled annual audiogram showing resolution. A same-year retest showing improvement does not qualify as the basis for removal — it must be the audiogram conducted in the following calendar year or the next annual test cycle. Additionally, removal is only appropriate when the threshold shift has fully resolved to below recordability criteria — partial improvement is not sufficient for removal.
The Six Most Common 300 Log Recordkeeping Mistakes
Figure 7 — The Six Most Common OSHA 300 Log Hearing Loss Recordkeeping Errors
Each error is either an under-recording or over-recording problem — both create inspection exposure.
#
Mistake
Type
Correct Approach
1
Recording every STS automatically without checking the 25 dB total level threshold
Over-recording
Check both conditions: STS AND total level ≥ 25 dB HL from audiometric zero
2
Measuring the 25 dB threshold from the baseline audiogram instead of from audiometric zero (0 dB HL)
Under-recording
The 25 dB comparison is always to audiometric zero, regardless of baseline
3
Classifying hearing loss as an injury (Column J) instead of an illness (Column M3)
Misclassification
Hearing loss = illness. Always Column M(3).
4
Applying age correction inconsistently — some workers corrected, others not, with no documented policy
Process error
Adopt and document a consistent age correction policy applied uniformly across the workforce
5
Removing a 300 Log entry based on a 30-day retest rather than the next annual audiogram
Under-recording
Removal only permitted based on next annual audiogram showing full resolution
6
Not recording cases where the PLHCP marked “STS confirmed” but did not explicitly address recordability
Under-recording
Employer is responsible for recordability check regardless of PLHCP language; do not rely on PLHCP to flag 300 Log requirement
Frequently asked questions
Does every OSHA STS require a 300 Log entry?
No. A recordable case under 1904.10 requires two conditions: an STS (10 dB average shift from baseline at 2000/3000/4000 Hz) AND a total hearing level at or above 25 dB HL averaged at those same frequencies — measured from audiometric zero. A worker with very good hearing who develops an STS may never meet the 25 dB total level threshold and therefore has no recordable case.
What is audiometric zero and how is it different from the baseline audiogram?
Audiometric zero (0 dB HL) is the ANSI-standardized reference for normal hearing in young adults — it is the same for everyone. The baseline audiogram is that specific worker’s pre-exposure hearing at the time of hire enrollment. The STS calculation compares annual results to the individual’s baseline. The 300 Log recordability calculation compares annual results to audiometric zero (25 dB HL). These are two different reference points producing two different calculations from the same audiometric data.
Can we use age correction to avoid recording a case?
Yes, if the age-corrected shift falls below 10 dB, the STS is considered not to have occurred and the case is not recordable. However, age correction must be applied consistently under a documented policy — you cannot selectively apply it case-by-case. The same approach (apply or don’t apply) must be used across all recordability determinations.
Who is responsible for making the 300 Log recordability determination?
The employer is legally responsible for the recordability determination and the 300 Log entry, not the PLHCP. The PLHCP provides clinical findings (STS, work-relatedness opinion) that feed into the determination, but the employer must perform the 1904.10 calculation and make the final recording decision. Employers who wait for the PLHCP to “flag” recordable cases may miss entries when PLHCP reports do not explicitly address 300 Log obligations.
Is there a deadline for recording hearing loss cases on the 300 Log?
Under 1904.29, employers must enter each recordable case on the 300 Log within 7 calendar days of receiving information that a recordable case has occurred. For hearing loss, this typically means within 7 days of receiving the PLHCP’s report confirming STS and work-relatedness, once the employer has completed the 1904.10 two-condition check.
300 Log Determinations Pre-Calculated in Every Report
Soundtrace audiometric reports include 300 Log recordability determinations from the reviewing PLHCP — so you always know whether a case requires a log entry, with the clinical reasoning documented.
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