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In this lesson
What you'll learn
- Know when Subpart AA applies instead of 1910.146
- Describe the roles of host employer, controlling contractor and entry employer
- List the main requirements Subpart AA adds or changes
- Explain training and language requirements in construction
OSHA's construction confined space standard, 29 CFR 1926 Subpart AA (1926.1200 to 1926.1213), took effect in August 2015. It covers construction work in confined spaces, which before then fell under a short training requirement. The core concepts match 1910.146, with additions for the realities of construction sites.
Which standard applies?
- Construction work (building, altering, repairing, including painting and decorating) in a confined space: Subpart AA.
- Maintenance, inspection and other general industry work: 1910.146.
The same space can fall under either one depending on the work. Building a new pump station is construction; routine cleaning of the wet well later is general industry. See our page on construction vs. general industry training.
Who does what on a multi-employer site
Subpart AA defines roles for employers who share a site:
| Role | Who | Key duties |
|---|---|---|
| Host employer | The employer that owns or manages the property | Share information about known permit spaces, hazards and previous entries with the controlling contractor |
| Controlling contractor | The employer with overall responsibility for construction at the site | Get information from the host, pass it to entry employers, coordinate entries when more than one employer works in or near a space, debrief after entry |
| Entry employer | Any employer that decides an employee it directs will enter a permit space | Run the permit program for its employees, coordinate with the controlling contractor, report hazards found |
The controlling contractor must coordinate entry operations when more than one entry employer is working, or when other activities nearby could create hazards in the space.
What Subpart AA adds or changes
According to OSHA, the main differences from 1910.146 are:
- A competent person must evaluate the worksite and identify confined spaces, including permit spaces, before work begins.
- More detailed multi-employer coordination among host employers, controlling contractors and entry employers.
- Continuous atmospheric monitoring whenever possible.
- Continuous monitoring of engulfment hazards, with an early-warning system for non-isolated engulfment hazards, such as upstream flows in a sewer.
- Permit suspension: an entry permit may be suspended, instead of canceled, for a temporary change in conditions, as long as the space is returned to the acceptable entry conditions before re-entry.
- Coordination with emergency services: employers relying on local emergency services must arrange for them to give advance notice if they will be unavailable.
- Clarified requirements such as training in a language and vocabulary the worker understands, and additional definitions such as "entry employer," "entry rescue," "early-warning system" and "physical hazard."
Training in construction
Under 1926.1207, the employer must provide training at no cost to the employee:
- Before the employee is first assigned duties under the standard,
- Before a change in assigned duties,
- Whenever there's a change in permit space operations that presents a hazard the employee wasn't trained for, and
- Whenever there's evidence of deviations or inadequacies in the employee's knowledge or use of procedures.
Training must establish proficiency, be provided in a language and vocabulary the employee understands, and be certified with the employee's name, the signatures or initials of the trainers, and the dates of training. The certification must be available for inspection.
Common construction confined spaces
Attics, crawl spaces, sewers, manholes, pits, tanks, vaults, boilers, HVAC ducts, storm drains, drilled shafts, enclosed beams, lift stations and precast concrete structures are all frequently encountered. See more in confined space examples.
Key takeaways
- Subpart AA covers construction work in confined spaces; 1910.146 covers general industry work.
- Host employer shares information; controlling contractor coordinates; entry employer runs the entry.
- Subpart AA adds a competent person, continuous monitoring, engulfment early warning, permit suspension and emergency service notice.
- Training must be in a language the worker understands and must be certified.
Knowledge check
Lesson 12 quiz: 8 questions
Choose one answer for each question, then select Check my answers. Score 80%% or higher to pass. Your answers stay in your browser and are never saved.
Sources and official references
Last reviewed: October 25, 2026 · Free general education based on OSHA 29 CFR 1910.146 and 29 CFR 1926 Subpart AA. It does not replace the site-specific training, written program and hands-on evaluation your employer must provide, and it does not issue a certificate. Nothing you enter on this page is saved or sent.