29 CFR 1926 Subpart AA: OSHA Confined Spaces in Construction

Regulatory citation: 29 CFR Part 1926, Subpart AA, Confined Spaces in Construction (1926.1200–1213)

What Is the OSHA Confined Spaces in Construction Standard?

Subpart AA protects construction workers who work in or near confined spaces such as manholes, crawl spaces, tanks, pits, vaults and attics. It applies to construction activities at a worksite with one or more confined spaces. Section 1926.1200 is reserved, so the rules run from 1926.1201 to 1926.1213.

Why Confined Space Rules Matter in Construction

Construction sites change daily, and so can the hazards in and around a confined space. Planning entry and rescue before work starts is essential.

Core Obligations

1. Identify Spaces Before Work Starts (1926.1203(a)–(c))

Before work begins, a competent person must identify all confined spaces employees may work in and decide which are permit-required confined spaces. A permit space is a confined space with a potential hazardous atmosphere, potential for engulfment, an inward-converging or tapering layout that could trap or asphyxiate an entrant, or any other serious safety or health hazard. Exposed employees must be warned by signs or equally effective means, and employers that do not allow entry must take effective steps to prevent it.

2. Exchange Information Between Employers (1926.1203(h) and (i))

The host employer must tell the controlling contractor what it knows about permit spaces and their hazards. The controlling contractor must pass this to each entry employer, coordinate entry when more than one employer works in or near a space, and debrief entry employers afterward. No one is required to enter a space just to collect this information.

3. Write a Permit Space Program (1926.1203(d) and 1926.1204)

An entry employer that allows employees into permit spaces must have a written program available for inspection. The program must cover preventing unauthorized entry, identifying hazards, setting acceptable entry conditions, isolating hazards, ventilating, providing equipment at no cost, assigning at least one attendant and coordinating with other employers. Canceled permits must be reviewed within 1 year after each entry, and a single annual review may cover all entries in a 12-month period.

4. Test and Monitor the Atmosphere (1926.1202 and 1926.1204(e))

Testing must check oxygen first, then combustible gases and vapors, then toxic gases and vapors. A hazardous atmosphere includes oxygen below 19.5% or above 23.5%, flammable gas or vapor above 10% of its lower flammable limit, combustible dust at or above its lower flammable limit, and any substance above its permissible exposure limit. Atmospheric hazards must be monitored continuously unless the employer can show that equipment is not commercially available or that periodic monitoring is enough.

5. Use Permits for Each Entry (1926.1205 and 1926.1206)

A permit must be completed before entry and signed by the entry supervisor, and posted at the entry portal or otherwise made available to entrants. It must list the space, purpose, date and duration, entrants, attendants, entry supervisor, hazards, controls, acceptable conditions, test results, rescue services and communication methods. A permit may not last longer than the time needed for the task, must be suspended or canceled when conditions change, and canceled permits must be kept for at least 1 year.

6. Use Alternate Procedures Only When Conditions Are Met (1926.1203(e) and (g))

Some spaces may be entered under alternate procedures when all physical hazards are eliminated or isolated, continuous forced-air ventilation alone keeps the space safe, and monitoring data supports this. A permit space may be reclassified as a non-permit space only when a competent person certifies that all hazards are eliminated or isolated. Ventilation alone does not count as elimination.

7. Train Entrants, Attendants and Supervisors (1926.1207–1210)

Training must be given at no cost and in a language and vocabulary employees understand. It is required before first assignment, before duties change, when new hazards arise and when the employer finds deviations or gaps in knowledge. Records must show each employee's name, the trainers and the dates. Attendants must stay outside the space until relieved.

8. Plan Rescue Before Entry (1926.1211)

Employers must evaluate rescue services for response time and capability. Rescue team members need training and PPE, at least one must hold current first aid and CPR certification, and practice rescues must be held at least every 12 months unless a real rescue was performed in a similar space in that period. Non-entry rescue equipment is required unless it would increase risk, and a mechanical device is required to retrieve entrants from vertical spaces more than 5 feet deep.

Common Compliance Approaches

Site Confined Space Register

Controlling contractors keep a live list of spaces, their classification and the employers working in them, updated as the building progresses.

Example: Confined Spaces in Construction in Practice

A general contractor is building a water treatment facility with several underground valve vaults. Its competent person classifies the vaults as permit spaces and marks them with signs. The owner, as host employer, shares records of past hydrogen sulfide readings. An electrical subcontractor that needs to pull cable through a vault receives this information, writes a permit, uses a four-gas monitor with continuous alarms, and sets up a tripod and winch because the vault is 9 feet deep.

Related regulations: OSHA permit-required confined spaces (general industry), OSHA excavations, OSHA construction general safety and training.

Note: Subpart AA does not apply to work covered by Subpart P (excavations), Subpart S (underground construction, caissons, cofferdams and compressed air) or Subpart Y (diving). Where another standard also addresses a confined space hazard, both apply. State plan states may set stricter rules.

Frequently Asked Questions

Who decides whether a space is a permit space?

A competent person must identify confined spaces and permit spaces before work begins.

Can ventilation alone make a permit space safe to enter without a permit?

Ventilation alone cannot be used to reclassify a space. It may support entry under alternate procedures, but only if all physical hazards are eliminated or isolated and monitoring data supports it.

How long must permits be kept?

Canceled entry permits must be retained for at least 1 year and used in the annual program review.