29 CFR § 1910.146 — Permit-required confined spaces
29 CFR — Labor · OSHA / DOL
29 CFR 1910.146 governs entry into permit-required confined spaces — tanks, vessels, silos, vaults, sewers, manholes, pipelines, and similar spaces with limited entry/exit and one or more recognized hazards. Required: written program, PRCS identification/labeling, pre-entry permit, atmospheric testing (oxygen, flammables, toxics), trained personnel (authorized entrant, attendant, entry supervisor), and rescue arrangements. Confined-space fatalities are frequently multi-fatality events because untrained 'rescuers' often die alongside the original entrant. OSHA's PRCS standard is among the most thoroughly enforced; 60%+ of confined-space fatalities involve no permit or program.
Regulation summary
29 CFR 1910.146 establishes safety procedures for entry into permit-required confined spaces (PRCS) — confined spaces with one or more of the following hazards: hazardous atmosphere, material that could engulf an entrant, internal configuration that could trap or asphyxiate, or other recognized serious safety/health hazard. Required elements: written permit-required confined space program; identification and labeling of all PRCS; entry permit completed before each entry; pre-entry atmospheric testing; trained authorized entrants, attendants, and entry supervisors; rescue arrangements; and post-entry permit closure.
Who must comply
General industry employers with permit-required confined spaces in their workplaces. Construction-industry PRCS rules are in 29 CFR 1926 Subpart AA (effective 2015). Maritime has separate PRCS standards under 1915/1917/1918.
What happens if violated
Serious violation penalties: up to $16,131. Willful or repeat: up to $161,323. PRCS fatalities almost always result in willful classifications. Multi-fatality incidents trigger criminal referrals to DOJ in some cases. Civil litigation exposure is severe.
Implementation checklist
- Identify all confined spaces in your facility.
- Determine which are PERMIT-required (have one or more recognized hazards).
- Label PRCS or otherwise inform employees they exist (signs, warning communications).
- Develop a written PRCS program covering pre-entry, entry, and post-entry procedures.
- Train authorized entrants, attendants, and entry supervisors on their specific roles.
- For each entry, complete a written permit covering: testing results, ventilation, communications, rescue, supervisor signature.
- Conduct pre-entry atmospheric testing (oxygen, flammables, toxics) and continuous monitoring during entry.
- Arrange for emergency rescue — either trained on-site rescue team or designated off-site service.
- Close out the permit at end of entry.
- Coordinate with contractors performing PRCS work in your facility.
- Annually review the program and update for new spaces or changes.
Common misinterpretations
- Misinterpretation: 'It's a tank — that's just a confined space.' Reality: A confined space without hazards is a 'non-permit' confined space and has different (lighter) requirements. PRCS adds hazardous atmosphere, engulfment, trapping, or other serious hazards on top of the confined-space definition. The distinction determines program requirements.
- Misinterpretation: 'My contractor handles their own PRCS.' Reality: 29 CFR 1910.146(c)(8) requires the HOST employer to inform the contractor of PRCS, provide hazard information, coordinate entries with multi-employer worksites, and require contractor compliance with 1910.146. Host responsibility doesn't transfer.
- Misinterpretation: 'Atmospheric testing is just oxygen.' Reality: Pre-entry testing must cover: oxygen (must be 19.5-23.5%), flammable gases/vapors (must be <10% LEL), and toxic atmospheric contaminants (must be below permissible exposure limits). All three categories.
- Misinterpretation: 'My attendant can rescue the entrant.' Reality: 29 CFR 1910.146(i) prohibits the ATTENDANT from entering the space to rescue. Attendant maintains communication, monitors, and SUMMONS RESCUE — but does not enter. Untrained 'attendant rescues' are a leading cause of multi-fatality PRCS incidents.
Frequently asked questions
What is a permit-required confined space?
A confined space (limited entry/exit, not designed for continuous occupancy, large enough to enter and perform work) that ALSO contains one or more of: hazardous atmosphere, material that could engulf, internal configuration that could trap or asphyxiate, or other recognized serious safety/health hazards.
What's the difference between PRCS and non-permit confined spaces?
Non-permit confined spaces meet the confined space definition but have NO recognized hazards. They have lighter requirements (basic awareness, no permit, no atmospheric testing required). PRCS adds the hazard component — and therefore the permit, testing, training, and rescue requirements.
Do I need a permit for every entry?
Yes, for permit-required spaces. Each entry requires a written permit covering atmospheric testing, ventilation, communications, rescue arrangements, and supervisor signature. The permit must be completed BEFORE entry and posted at the entry point.
Who needs PRCS training?
(1) Authorized entrants — workers who enter the space. (2) Attendants — workers stationed outside who monitor entrants. (3) Entry supervisors — designated supervisors who authorize entry. Each role has specific training requirements per 29 CFR 1910.146(g) and (k).
Can the attendant enter to rescue?
NO. 29 CFR 1910.146(i) prohibits the attendant from entering the space to rescue. The attendant maintains communications, monitors, and SUMMONS RESCUE. Untrained 'attendant rescues' are a leading cause of multi-fatality PRCS incidents — the would-be rescuer is overcome by the same hazard.
What pre-entry testing is required?
Atmospheric testing for: (1) oxygen (must be 19.5-23.5%), (2) flammable gases/vapors (must be <10% Lower Explosive Limit), (3) toxic atmospheric contaminants (must be below permissible exposure limits). All three categories before entry, and continuous monitoring during entry. Testing equipment must be calibrated and the operator must be trained.
How do I arrange rescue?
Either: (1) an in-house trained rescue team that can respond within a meaningful timeframe (typically <4 minutes for atmospheric hazards), OR (2) a designated off-site rescue service that the employer has evaluated for capability and communicated PRCS-specific hazards. Calling 911 alone is not 'arranged rescue' — local fire/EMS may not be trained or equipped for confined-space rescue.
Cross-references: 29 CFR 1910.134 · 29 CFR 1910.147 · 29 CFR 1910.132 · 29 CFR 1926.1200
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