Mining employers operate under MSHA 30 CFR Part 62, not OSHA 1910.95. While the two standards share similar exposure limits and both require hearing conservation programs, they diverge in important ways: different audiometric definitions of a hearing loss event, different reporting pathways, and a specific dual hearing protection requirement that OSHA’s standard does not have. This guide covers every meaningful difference between Part 62 and 1910.95, with a focus on what mining employers must know to maintain compliance under both agencies when operations have any overlap with general industry.
- MSHA jurisdiction: which operations are covered
- Part 62 vs. 1910.95: full comparison
- Action level and PEL: same numbers, separate authority
- OSHA STS vs. MSHA reportable hearing loss
- Dual hearing protection: Part 62’s 105 dBA trigger
- Part 50 reporting: mining’s government reporting requirement
- Jurisdictional overlap: when both standards apply
- Frequently asked questions
MSHA Jurisdiction: Which Operations Are Covered
The Mine Safety and Health Administration (MSHA) has jurisdiction over all surface and underground mining operations in the United States under the Federal Mine Safety and Health Act of 1977. This includes:
- Coal mines (surface and underground)
- Metal mines (gold, silver, copper, zinc, lead, iron)
- Nonmetal mines (limestone, gypsum, potash, sand and gravel, phosphate, industrial minerals)
- Stone quarries and gravel pits
- Mill operations directly associated with a mine (ore processing, preparation plants)
MSHA jurisdiction begins at the mine entrance and covers all mining operations and milling conducted at the mine site. Contract workers performing mining work at an MSHA-covered site are covered by MSHA standards, not OSHA. The key test is whether the work is performed at or constitutes a mining operation.
Part 62 vs. 1910.95: Full Comparison
Action Level and PEL: Same Numbers, Separate Authority
Both MSHA Part 62 and OSHA 1910.95 use an 85 dBA TWA action level and a 90 dBA TWA PEL. Both use a 5 dB exchange rate. Despite identical numerical thresholds, they are separate legal obligations administered by separate agencies with separate inspection programs, separate citation pathways, and separate penalty structures. An employer cannot cite compliance with OSHA as a defense to an MSHA citation, or vice versa.
OSHA STS vs. MSHA Reportable Hearing Loss: The Threshold Gap
The most operationally significant difference between the two standards is the audiometric event that triggers follow-up obligations:
- OSHA STS: An average change in hearing threshold of 10 dB or more at 2,000, 3,000, and 4,000 Hz in either ear. This triggers notification, HPD refit, and possible 300 log recordability.
- MSHA Reportable Hearing Loss: An average change in hearing threshold of 25 dB or more at 2,000, 3,000, and 4,000 Hz in either ear. This triggers miner notification and Part 50 reporting to MSHA.
The 15 dB gap between the thresholds is significant. An MSHA-covered miner can have an audiometric shift of 20 dB — well above OSHA’s STS threshold — without triggering any MSHA reporting obligation. This makes MSHA’s surveillance system less sensitive to early hearing loss than OSHA’s.
Dual Hearing Protection: Part 62’s Explicit 105 dBA Trigger
30 CFR 62.170(b) explicitly requires miners to use both earplugs and earmuffs simultaneously when exposure equals or exceeds 105 dBA TWA. No equivalent provision exists in OSHA 1910.95. For mining employers:
- Jobs involving continuous miners, longwall shearers, rock drills, and high-speed machinery commonly generate TWAs above 105 dBA
- Single HPD devices — even high NRR earmuffs — typically cannot provide the 15–20 dB of attenuation needed to bring 105+ dBA exposures below the PEL
- The combination of earplugs and earmuffs provides approximately 3–5 dB more attenuation than the higher-rated single device
- Documentation of dual HPD issuance and use must be maintained
Part 50 Reporting: Mining’s Government Reporting Requirement
Under 30 CFR Part 50, mining operators must report occupational injuries and illnesses to MSHA. Hearing loss events that meet the Part 62 reportable threshold (25 dB average shift at 2k/3k/4k Hz) must be reported. Unlike OSHA’s 300 log (which is retained by the employer), MSHA Part 50 reports go directly to the federal government — creating a government-maintained audiometric event record.
The reporting timeline under Part 50 is typically within 10 working days of the event becoming known. Mining operators should have a clear workflow for identifying reportable hearing loss events during the audiometric testing process.
Jurisdictional Overlap: When Both Standards Apply
True dual jurisdiction is rare but possible. Situations where both standards could theoretically apply include:
- A mine operator who also runs a separate manufacturing facility at the same property — the manufacturing operation is OSHA-covered, the mining operation is MSHA-covered
- Contractors performing non-mining maintenance work at a mine site — jurisdiction analysis depends on the nature and location of the work
- Sand and gravel operations that also produce processed aggregate products — the mining extraction is MSHA-covered; downstream manufacturing may be OSHA-covered
Federal employees working at mine sites are subject to 29 CFR Part 1960, which generally incorporates 1910.95 requirements. Simultaneously, if they are performing mining operations at an MSHA-covered site, MSHA jurisdiction may also apply. This overlap is relatively rare but requires specific jurisdictional analysis.
Frequently Asked Questions
Mining operations are governed by MSHA 30 CFR Part 62, not OSHA 1910.95. MSHA has exclusive jurisdiction over mining operations under the Federal Mine Safety and Health Act. OSHA does not have authority over mining operations. Contract workers performing mining work at an MSHA-covered site are covered by MSHA, not OSHA, regardless of the worker’s employer.
OSHA’s STS threshold is a 10 dB average shift at 2,000, 3,000, and 4,000 Hz — triggering worker notification, HPD refit, and possible 300 log recordability. MSHA’s reportable hearing loss threshold is 25 dB average shift at the same frequencies — triggering miner notification and Part 50 reporting to MSHA. A 20 dB shift triggers OSHA follow-up but not MSHA reporting.
30 CFR 62.170(b) requires miners to use both earplugs and earmuffs simultaneously when noise exposure equals or exceeds 105 dBA TWA. This is an explicit requirement in the MSHA standard with no equivalent in OSHA 1910.95. Continuous miners, rock drills, and other high-noise equipment commonly produce TWAs above this level.
Yes. Under 30 CFR Part 50, mining operators must report occupational illnesses including hearing loss events that meet the Part 62 reportable threshold (25 dB average shift) to MSHA, typically within 10 working days. OSHA does not require employers to report hearing loss events to OSHA — only to record them on the internal 300 log.
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