Under 29 CFR 1926 Subpart AA, every contractor whose workers may enter a permit-required confined space must run a written program, issue permits, test the atmosphere, station a trained attendant, and have a rescue plan in place before anyone crosses the opening plane.
What Law Governs Confined Spaces on Construction Sites?
Construction confined spaces fall under 29 CFR 1926 Subpart AA (sections 1926.1200–1926.1213), which became effective August 3, 2015. If your workers are on a construction site — not inside a permanent facility — this is the standard that applies, not 1910.146. The two standards share the same definitional framework, but 1926 Subpart AA makes controlling-contractor coordination duties more explicit.
If you operate in a state-plan jurisdiction (California, Michigan, Washington, and others), verify state-specific requirements separately. State-plan rules can be more stringent than the federal standard.
How Do You Know If a Space Is Permit-Required?
Start with the two-step classification. A space is a confined space when all three conditions are true simultaneously:
- Large enough for an employee to bodily enter and perform work
- Limited or restricted means for entry or exit
- Not designed for continuous employee occupancy
If any one of those three is absent, the space is not a confined space under the regulation.
A confined space becomes permit-required when it also has at least one of these characteristics (per 29 CFR 1926.1202):
| Characteristic | What It Means in Practice |
|---|---|
| Contains or may contain a hazardous atmosphere | "May contain" is enough — untested air qualifies |
| Contains material that could engulf an entrant | Grain, sand, liquid, any flowable solid |
| Inwardly converging walls or tapering floor | Could trap or asphyxiate even without fill material |
Classification is not a one-time task. A non-permit space becomes permit-required the moment work introduces a new hazard — hot work, chemicals, a loss of ventilation. Document your hazard reassessment for each entry.
"Entry" begins the instant any part of a worker's body breaks the plane of the opening. Atmospheric testing, permits, and attendants must be in place before a worker leans in to look or take a sample.
Employer Obligation 1: Evaluate and Communicate
Before any entry, you must survey the worksite and identify every confined space. For each permit-required confined space, you must inform exposed employees of its existence, location, and danger — through posted danger signs or equally effective means. The required sign language under 29 CFR 1910.146(c)(2), adopted by reference in the construction standard, is:
> DANGER — PERMIT-REQUIRED CONFINED SPACE, DO NOT ENTER
"Exposed employees" includes maintenance workers, delivery personnel, adjacent-trade contractors, and anyone whose routine duties bring them near the opening — not only workers who will enter.
Signs must be legible and in a language workers understand. OSHA has made clear that faded signs or English-only signs posted for a non-English-speaking workforce are treated as no sign at all. When a cover or manhole lid is removed during work, add a physical barrier — a railing or temporary cover — per 29 CFR 1910.146(c)(5)(ii)(B), not just a sign.
Employer Obligation 2: Written Permit Program
If any worker will enter a permit-required confined space, you must develop and implement a written permit-required confined space program (29 CFR 1910.146(c)(4), incorporated by reference). The program must address how you will:
- Identify and classify all permit spaces
- Test and monitor the atmosphere
- Isolate energy sources and control hazards
- Issue, control, and cancel entry permits
- Train entrants, attendants, and supervisors
- Provide and maintain rescue services
- Review canceled permits at least annually
The program is not a form — it is a management system. An annual review using canceled permits is required; a stack of old permits sitting in a drawer is not a review. OSHA expects documented evidence of what was evaluated and what changed.
Employer Obligation 3: Atmospheric Testing Before and During Entry
Before anyone enters, you must test the internal atmosphere with a calibrated direct-reading instrument. The testing sequence is fixed (29 CFR 1910.146(d)(5)(i)):
1. Oxygen — acceptable range is 19.5% to 23.5% by volume 2. Flammable gases/vapors — must be below 10% of the Lower Flammable Limit (LFL) 3. Toxic air contaminants — must be below applicable permissible exposure limits
The order matters. Oxygen levels affect how combustible-gas meters read, so you test oxygen first.
Testing must be stratified. Gases have different vapor densities: hydrogen sulfide sinks to the bottom, methane rises to the top, carbon monoxide distributes throughout. Test at the top, middle, and bottom of vertical spaces. Allow approximately one second of instrument draw time per foot of sample hose, plus sensor response time, before reading each level. A single reading at the opening is an enforcement target.
Bump-test monitors before each shift. A monitor that has not been bump-tested against known gas is not a "calibrated direct-reading instrument" for OSHA purposes. Zero the instrument in verified fresh air — never inside a vehicle or near an idling engine.
When the permit specifies continuous monitoring, the atmosphere must be tested throughout the entry. If ventilation is stopped for any reason, re-test and re-authorize before re-entry.
Employer Obligation 4: Isolate Every Energy Source
Closing a valve is not isolation. Per 29 CFR 1910.146(d)(3)(i), acceptable isolation methods are:
- Blanking or blinding (solid plate fastened over the bore)
- Misaligning or removing sections of lines, pipes, or ducts
- Double block and bleed
For mechanical energy, lockout/tagout per 29 CFR 1910.147 applies. Stored or residual energy — spring tension, hydraulic pressure, gravity — must be relieved or restrained before entry is authorized.
For spaces with engulfment hazards such as augers, hoppers, or grain bins, physical isolation means locking out discharge gates, blanking liquid lines, and blocking material flow — not switching off a control panel.
The entry supervisor must physically verify isolation before signing the permit. A signature based on a verbal report from someone else is a common citation.
Employer Obligation 5: Issue a Complete Entry Permit
An entry permit is the formal authorization that makes entry lawful. Per 29 CFR 1910.146(f)(3), every permit must include:
- Specific location identification of the space
- Purpose of the entry and authorized duration
- Names of authorized entrants, the attendant, and the entry supervisor
- Known hazards of the space
- Isolation and control measures in place
- Actual numerical atmospheric test results ("OK" or "Safe" is a violation)
- Names or initials of testers with time of testing
- Rescue services and means of summoning them
- Communication procedures
- Required equipment
- Any additional permits (e.g., hot work)
The entry supervisor's signature is a certification of firsthand verification — not a remote sign-off from a truck or office. The permit is canceled when entry is complete or when any prohibited condition arises in or near the space. Canceled permits must be retained for at least one year (29 CFR 1910.146(e)(6)) to support the annual program review.
Employer Obligation 6: Assign and Train an Attendant
An attendant must be stationed outside the space for every permit entry. The attendant's duties under 29 CFR 1910.146(i) are non-delegable and non-interruptible:
- Maintain an accurate count of who is inside
- Communicate continuously with entrants
- Monitor inside and outside conditions
- Order immediate evacuation when any mandatory trigger occurs
- Summon rescue services if entrants may need assistance
- Remain at the portal until relieved by another trained attendant
Assigning secondary tasks — forklift operation, tool running, paperwork away from the opening — is a violation. The attendant cannot enter the space as part of their response. Non-entry rescue is the required first response.
Mandatory evacuation triggers are not judgment calls. The attendant must order evacuation when:
- Any gas-monitor alarm sounds
- A prohibited condition is detected
- An entrant shows behavioral signs of exposure (confusion, slurred speech, loss of coordination, silence)
- An external hazard arises
- The attendant cannot safely perform all required duties
If communication is lost for any reason, entry must terminate immediately.
Employer Obligation 7: Provide Non-Entry Rescue Capability
Approximately 60% or more of confined space fatalities involve would-be rescuers who entered without proper equipment and were overcome by the same hazard that incapacitated the original victim. The regulation addresses this directly.
Per 29 CFR 1910.146(k)(3), a retrieval system must be used for every entry unless the employer documents that it would increase overall risk or would not contribute to rescue. Required components:
- A chest or full-body harness with the retrieval line attached at the center of the back near shoulder level or above the head
- A retrieval line connected to a mechanical device or fixed anchor outside the space
- A mechanical retrieval device for any vertical space more than 5 feet deep — this threshold is exact and non-negotiable
A fall-arrest self-retracting lifeline is not a retrieval device. It stops a fall but cannot crank an incapacitated worker back to the surface. If your tripod is equipped only with a fall-arrest block and no winch or mechanical-advantage crank, you are not in compliance with the retrieval requirement.
The attendant must be trained on the specific retrieval equipment on-site and must have practiced the extraction before an emergency occurs.
Shift Turnovers and Reclassification
Shift turnovers: Multiple people may serve as entry supervisor in succession during a single entry. Each incoming supervisor must independently verify that entry conditions remain consistent with the permit before assuming responsibility. Simply handing over a clipboard is not a transfer of authority — it is a citation waiting to happen.
Reclassification: A permit-required confined space can be reclassified as a non-permit space only if the sole hazard is atmospheric and continuous forced-air ventilation alone keeps conditions within acceptable limits (29 CFR 1910.146(c)(7)). Any physical, mechanical, or engulfment hazard disqualifies reclassification entirely. Reclassification certifications must be re-verified before each entry — a one-time document does not cover ongoing or future entries.
Training Requirements
Training is required before a worker's first assignment in each role and must be repeated whenever duties change, hazards change, procedures change, or the employer has reason to believe proficiency has lapsed (29 CFR 1926.1207). Training must be documented in writing and must include each employee's name, the trainer's attestation, and the date. Generic LMS completion records without trainer attestation have been cited.
Three distinct roles require role-specific training:
| Role | Core Training Content |
|---|---|
| Authorized Entrant | Hazards, PPE use, communication duties, evacuation obligations |
| Attendant | Hazard recognition, behavioral signs of exposure, evacuation triggers, rescue summoning, no-entry rule |
| Entry Supervisor | All of the above, plus permit completion, isolation verification, and rescue service validation |
Jobsite tracks OSHA training, certifications, and inspection records for contractors — so your confined space program documentation is audit-ready when OSHA shows up. [See how Jobsite supports safety compliance →](/product/safety-compliance)
FAQ
Does 29 CFR 1926 Subpart AA apply to construction workers entering a permanent facility's confined spaces?
It depends on who controls the space. If your workers are entering a space as part of a construction project, 1926 Subpart AA applies. If they are entering a permanent facility operated by a host employer under general industry conditions, 29 CFR 1910.146 may govern instead — and the host employer's coordination duties under 1910.146(c)(8)–(9) come into play. Verify which standard applies with your safety counsel before your program is written.
Can the entry supervisor also serve as the attendant?
Technically yes, but it creates serious operational conflicts. The attendant must remain at the portal at all times until relieved by another trained attendant. If the entry supervisor takes on that role, they cannot leave to manage overall site safety, coordinate with emergency services, or supervise other work. OSHA's guidance and field experience both flag this dual assignment as a compliance risk except for the smallest, lowest-hazard entries.
How long must canceled entry permits be kept?
At least one year, per 29 CFR 1910.146(e)(6). Canceled permits must be reviewed as part of the annual program review. The review must produce documented evidence — a memo, summary, or meeting minutes — showing what was evaluated and what changed. A stack of permits in a drawer without a documented review does not satisfy the requirement.
What triggers mandatory retraining under the construction confined space standard?
Per 29 CFR 1926.1207(c), retraining is required when an employee's duties change, when permit space operations or hazards change, when a deviation from permit procedures occurs, or when the employer has reason to believe the employee's knowledge or proficiency is inadequate. There is no fixed federal calendar interval; the trigger is event-based. Many employers use a 12-month default as a best practice to stay ahead of these triggers.
Cited standards
See how Jobsite handles this in practice: Safety & compliance on the platform →
About the author
The Jobsite Editorial Team — Construction safety & OSHA compliance
The Jobsite Editorial Team writes the safety and compliance library behind Jobsite, the construction safety, OSHA compliance, and training platform for contractors. Every article starts from the primary regulatory text — the CFR section itself, not a summary of it — and is fact-checked against that source before it publishes, so what you read here is what the standard actually requires of small and mid-size contractors in the field.