Regulatory Comparison
Construction vs. General Industry
Two OSHA standards cover confined spaces. Which one applies depends on the type of work, not the industry your company is generally in.
29 CFR 1926 Subpart AA
Applies to confined space work on construction sites. Adopted after 1910.146 to address challenges unique to construction: multiple employers on one site, constantly changing hazards, and shifting work areas.
- Continuous atmospheric monitoring requirements
- Information exchange rules between employers on multi-employer sites
- Explicit Competent Person program-oversight role
29 CFR 1910.146
Applies to permit-required confined space work outside of construction: manufacturing, utilities, water/wastewater, warehousing, and similar general industry settings.
- Same core roles: entrant, attendant, entry supervisor
- Written permit space program requirement
- No construction-specific multi-employer provisions
The deciding question: is this a construction site or construction activity (as OSHA defines it), or a general industry facility? Some companies operate under both standards depending on the job. Our Awareness, Entry, and Supervisor courses reference 1926 Subpart AA as the primary standard, with 1910.146 concepts covered where they overlap. See our full standards guide for details, and confirm with qualified counsel or OSHA if you're unsure which applies to your work.
Side by side
Where Subpart AA goes further than 1910.146
OSHA's construction rule took effect on August 3, 2015. It keeps the familiar framework of 1910.146 (permit spaces, entrants, attendants, entry supervisors, permits and rescue) and adds provisions aimed at the way construction sites work. OSHA has highlighted these key differences:
| Topic | 1926 Subpart AA (construction) | 1910.146 (general industry) |
|---|---|---|
| Identifying spaces | A competent person must identify confined spaces and permit spaces before work begins | The employer evaluates the workplace for permit spaces |
| Multi-employer sites | Detailed information exchange among host employers, controlling contractors and entry employers | More general host employer and contractor duties |
| Atmospheric monitoring | Continuous monitoring wherever possible | Periodic testing as necessary to confirm conditions |
| Engulfment hazards | Continuous monitoring of engulfment hazards, such as an early-warning system for upstream flows | Not addressed in the same detail |
| Changing conditions | A permit may be suspended for a temporary change and then resumed | The permit is canceled and a new one issued |
Deciding which standard applies
The question is what kind of work is being done, not what industry the company is in. A water utility, for example, may follow 1910.146 for routine maintenance in an existing vault and Subpart AA when crews are building or substantially altering a structure. OSHA's construction definitions generally cover construction, alteration and repair, including painting and decorating.
When the line is unclear, many employers train to the stricter construction provisions so crews are ready for either. Our OSHA standards guide links to the official text of both rules.
Common construction confined spaces
OSHA's examples of construction locations where confined spaces may occur include:
- Manholes, sewers, storm drains and transformer vaults
- Precast concrete and other pre-formed manhole units
- Tanks, boilers, bins, silos and vessels
- Pits, such as elevator, pump and valve pits
- HVAC ducts and water mains
- Drilled shafts and concrete pier columns
- Digesters, lift stations and cesspools
- In residential construction, attics and crawl spaces
See our free guide to confined space examples and the confined spaces in construction lesson for how each is evaluated.
Training under either standard
Both standards require training before an employee's first assigned duties, when duties change, when a change in operations creates a new hazard, and when the employer believes the employee's knowledge or use of procedures is inadequate. Subpart AA adds that training must be provided at no cost to the employee and in a language and vocabulary the employee understands. Both rules require the employer to keep a training certification with the employee's name, the trainer's signature or initials, and the dates of training.
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