Summary
In short
- OSHA 1910.146 requires a written entry permit before anyone enters a permit-required confined space, signed by an entry supervisor who verifies every condition on it before authorising entry.
- Atmospheric testing must follow a fixed order: oxygen first, then flammable gases and vapours, then toxic contaminants, because the instrument readings for the later tests are unreliable if oxygen is out of range.
- The attendant must remain outside the space for the whole entry and must never enter to attempt a rescue, because untrained would-be rescuers account for a large share of confined space fatalities.
- Rescue arrangements must be in place before entry, and where an outside rescue service is used the employer must have evaluated its ability to respond to that specific space, not merely have its phone number.
- A space can be reclassified as non-permit only where every hazard has been eliminated rather than controlled, which is documented under 1910.146(c)(7) and reverts the moment a hazard returns.
- General industry entries fall under 1910.146; construction work has a separate standard at 29 CFR 1926 Subpart AA with similar but not identical requirements.
What it is
What it is
What is a permit-required confined space?
A confined space is large enough to enter, has limited means of entry or exit, and is not designed for continuous occupancy. It becomes permit-required if it also contains or could contain a hazardous atmosphere, engulfment material, an inwardly converging configuration, or any other recognised serious hazard.
What is a confined space entry permit?
A confined space entry permit is the written authorisation issued by an entry supervisor before anyone enters a permit-required space. It records the hazards, the atmospheric test results, the isolation and ventilation in place, the entrants and attendant by name, and the rescue arrangements. It is valid only for the duration and conditions stated on it.
When to use it
When to use it, and when not to
Most confined space citations start with a classification error. A space that should have been permit-required was entered on a checklist, or a space with every hazard genuinely eliminated is still being permitted at full cost. Get the classification right and the rest of the programme follows.
Use it for
- The space meets all three criteria and contains or could contain a hazardous atmosphere, engulfment material, an inwardly converging configuration, or any other recognised serious hazard
- Entry is planned into a tank, vessel, silo, pit, sewer, duct, hopper or mixer where atmosphere cannot be guaranteed
- Hot work, coating, solvent use or welding will happen inside the space, which changes the atmosphere after testing has passed
- Contractors will enter a space you control, which triggers the host and outside employer duties under (c)(8)
- Any condition on a previous permit has changed, which requires a new permit rather than an extension
Not for
- Spaces where every hazard has been eliminated and the reclassification under (c)(7) is documented, which need an entry record rather than a permit
- Alternate procedure entries under (c)(5) where the only hazard is atmospheric and continuous forced ventilation controls it
- Construction work, which falls under 29 CFR 1926 Subpart AA with its own requirements
- Spaces designed for continuous occupancy, such as walk-in chillers with normal access and ventilation
- Work performed entirely from outside the space, where no part of the body breaks the plane of the opening
Standards
What it is built against
The permit is the artifact that proves the programme was applied to this entry. It does not replace the written programme, the training, or the rescue evaluation that sit behind it.
| Clause | Requirement | Where it lands |
|---|---|---|
| (f)(1) | Space to be entered identified on the permit | Header, space identification |
| (f)(2) | Purpose of the entry stated | Header, scope of work |
| (f)(3) | Date and authorised duration of the permit | Header, validity |
| (f)(4) | Authorised entrants identified by name or by a means of accurate identification | Personnel |
| (f)(5) | Attendants identified by name | Personnel, attendant |
| (f)(6) | Entry supervisor identified, with a space for the signature that authorises entry | Authorisation |
| (f)(7) | Hazards of the space identified | Hazard identification |
| (f)(8) | Measures used to isolate the space and eliminate or control hazards | Isolation and controls |
| (f)(9) | Acceptable entry conditions stated | Acceptable entry conditions |
| (f)(10) | Results of initial and periodic atmospheric tests, with tester and time | Atmospheric testing |
| (f)(11) | Rescue and emergency services, and how to summon them | Rescue |
| (f)(12) | Communication procedures between entrants and attendant | Communication |
| (d)(3)(iii) | Continuous or periodic monitoring as conditions require | Atmospheric testing |
What it does not cover
- The written permit space programme under (d), which identifies spaces, sets the evaluation process and governs contractors.
- Training and certification under (g) for entrants, attendants and entry supervisors, each with different duties.
- Rescue service evaluation under (k), which requires assessing whether the service can actually reach and extract from this space.
- Energy isolation, which needs a lockout/tagout procedure under 1910.147 where mechanical or electrical hazards are present.
- Hot work inside the space, which needs its own permit and its own controls.
The sequence
How the record runs
- 1
Identify the space and the work(f)(1)-(f)(3)
Name the space by its permanent identifier, not by description. State the specific task and the authorised duration. A permit valid for a shift does not cover the shift after it.
- 2
Identify the hazards(f)(7)
Atmospheric, engulfment, configuration, mechanical, electrical, thermal, noise, and anything introduced by the work itself. Welding, coating and solvent use change the atmosphere after testing has already passed.
- 3
Isolate and control(f)(8)
Blank, blind, double block and bleed, or physically disconnect. Lock out mechanical and electrical energy under 1910.147. Start ventilation and let it run long enough to turn the volume of the space over before testing.
- 4
Test the atmosphere in order(f)(10)
Oxygen first, then flammables, then toxics. The order matters because combustible gas indicators give unreliable readings in oxygen-deficient or oxygen-enriched atmospheres. Record the actual numbers, the instrument, its calibration date and the time.
- 5
Set acceptable entry conditions(f)(9)
State the numeric range that must hold for entry to continue, and what happens when it is breached. Evacuation must be automatic on alarm, not a judgement call made at the hatch.
- 6
Assign roles and confirm rescue(f)(4)-(f)(6), (f)(11)
Name every entrant, the attendant, and the entry supervisor. Confirm the rescue arrangement is available now, for this space, and that retrieval equipment is rigged where required. Only then does the supervisor sign.
Audit findings
Common audit findings
Confined space citations concentrate in a handful of places, and the pattern is consistent: the permit exists, but it does not reflect what actually happened at the space.
| Finding | Clause | What fixes it |
|---|---|---|
| Atmosphere not tested, or tested without recording the readings. | (d)(5) | Numeric results per gas, with instrument ID, calibration date, tester and time, before entry and at the stated monitoring interval. |
| Testing performed out of order, so flammable readings are unreliable. | (d)(5)(iii) | Enforce oxygen, then flammable, then toxic in the form order so the sequence cannot be skipped. |
| Permit incomplete or generic, with hazards and controls not specific to the space. | (f) | Space-specific permit drawn from the space register, with the twelve required elements each present. |
| No attendant, or the attendant left the space unmonitored. | (i) | Attendant named on the permit, relieved only by another named attendant, with the handover recorded. |
| Attendant entered the space to attempt a rescue. | (i)(6) | Non-entry retrieval rigged where feasible, and training that makes summoning rescue the only permitted action. |
| Rescue service named but never evaluated for this space. | (k)(1) | Documented evaluation of response time, equipment and ability to extract from that configuration, refreshed annually. |
| Energy sources not isolated before entry. | (d)(3)(ii) | Reference the machine specific energy control procedure on the permit and verify isolation before signing. |
| Space reclassified as non-permit while hazards were merely controlled by ventilation. | (c)(7) | Reclassify only where hazards are eliminated. Ventilation is control, not elimination, and reverts the space to permit-required. |
| Permit not cancelled when work ended or conditions changed. | (e)(5) | Cancellation and retention built into the closure step, with the cancelled permit kept for the annual programme review. |
| Contractor entry proceeding without exchange of hazard information. | (c)(8) | Documented briefing to the contractor covering the space hazards and the programme, and a debrief at the end. |
Worked case
Why the second body is the one that was preventable
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By jurisdiction
How the duty differs by jurisdiction
Confined space regimes are unusually consistent internationally, because the failure mode is the same everywhere: an entrant is overcome, and an untrained colleague goes in after them.
29 CFR 1910.146 (general industry); 29 CFR 1926 Subpart AA (construction)
Prescriptive. Twelve mandatory permit elements, defined roles, rescue evaluation.
The permit itself is the compliance artifact and is checked element by element.
CSA Z1006; provincial OHS regulations
Standard referenced, provincially enforced. BC OHSR Part 9 is among the more prescriptive.
Hazard assessment and written entry procedures required per space, with rescue provisions before entry.
Confined Spaces Regulations 1997; HSE ACOP L101
Duty based. Avoid entry where reasonably practicable; if entry is unavoidable, a safe system of work and adequate emergency arrangements are required.
No prescribed permit format, but a permit to work is the expected means of implementing the safe system of work.
Model WHS Regulations Part 4.3; AS 2865
Duty based. Entry permit required, risk assessment, atmospheric monitoring, standby person and emergency procedures.
The model regulations name the entry permit explicitly, which is closer to the US position than most WHS duties.
Definitions
Definitions and key terms
- Confined space
- Large enough to enter and perform work, with limited means of entry or exit, and not designed for continuous occupancy. All three must hold.
- Permit-required confined space
- A confined space that also has a hazardous atmosphere, engulfment potential, an inwardly converging shape, or any other recognised serious hazard.
- Authorised entrant
- An employee trained and authorised to enter, who must know the hazards, use equipment properly, communicate with the attendant and exit on alarm or order.
- Attendant
- The person stationed outside for the duration of entry, monitoring entrants and conditions and summoning rescue. Must never enter to rescue.
- Entry supervisor
- The person who verifies conditions, signs the permit to authorise entry, and cancels it when work ends or conditions change.
- Acceptable entry conditions
- The stated conditions that must exist for entry to be safe and to continue, usually expressed as numeric atmospheric ranges.
- Non-entry retrieval
- A harness and retrieval line rigged so a casualty can be extracted without anyone entering. Required where feasible and where it does not increase risk.
- Reclassification
- Downgrading a permit space to non-permit under (c)(7), permitted only where all hazards are eliminated, not controlled.
FAQ
Frequently asked questions
In what order should confined space atmospheric testing be done?+
Oxygen first, then flammable gases and vapours, then toxic contaminants. Combustible gas indicators depend on a normal oxygen level to give accurate readings, so testing for flammables in an oxygen-deficient or enriched atmosphere produces results you cannot rely on. Record actual numbers for each, with the instrument and time.
Can the attendant enter the space to rescue an entrant?+
No. Under 1910.146(i) the attendant must remain outside for the duration of entry operations until relieved by another attendant. The attendant's job is to summon rescue. Entrant-turned-rescuer behaviour is a leading cause of multiple-fatality confined space incidents, which is why the roles are separated in the standard.
How long is a confined space entry permit valid?+
For the duration stated on the permit, which cannot exceed the time required to complete the assigned task. The permit must be cancelled when the work is completed or when any condition it relies on changes. A new permit is required for a new shift, a new task, or a change in hazards.
When can a space be reclassified as non-permit?+
Only when all hazards within the space have been eliminated rather than controlled, with documented testing and inspection under 1910.146(c)(7). Continuous forced ventilation controls an atmospheric hazard, it does not eliminate it, so a ventilated space remains permit-required. If any hazard returns, the space reverts immediately.
Does the confined space standard apply to construction work?+
Not 1910.146. Construction has its own standard at 29 CFR 1926 Subpart AA, effective 2015. The requirements are similar in structure but not identical, particularly around continuous monitoring and multi-employer coordination on shared sites.
What has to be in place for rescue before entry begins?+
An arrangement that has been evaluated for this specific space, not just a contact number. Where an outside service is used, the employer must have assessed its ability to respond in time and extract from that configuration. Non-entry retrieval equipment must be rigged where feasible. Retrieval lines and harnesses that are stored rather than fitted do not count.
The agents
What the agents do with it
Permits fail between issue and closure. The atmosphere is tested once and never again, the attendant changes without a handover, the permit stays open after the crew has gone home.
Issues the permit against the space register, enforces the testing order, requires numeric readings, and forces cancellation at the stated expiry rather than letting it drift.
Holds the entrant, attendant and supervisor rosters separately, so a permit cannot name someone whose role training has lapsed.
Links the isolation on the permit to the machine specific energy control procedure for the equipment feeding the space.
Surfaces open permits, overdue monitoring intervals and rescue evaluations approaching expiry, and holds every write for approval.
This template lives in KnowSafe — safety and compliance. Incidents, hazards, permits, inspections and the critical controls behind them.
Meet KnowSafe→Sources
Sources
- 29 CFR 1910.146, Permit-required confined spaces
- 29 CFR 1910.146 Appendix C, example programmes
- 29 CFR 1926 Subpart AA, Confined spaces in construction
- CSA Z1006, Management of work in confined spaces
- Confined Spaces Regulations 1997 and HSE ACOP L101 (UK)
- Model WHS Regulations Part 4.3 and AS 2865 (Australia)