Confined spaces in construction: OSHA Subpart AA, explained
Confined spaces kill in ways that look preventable in hindsight — a bad atmosphere, an engulfment, a would-be rescuer overcome trying to help. OSHA's construction standard, 29 CFR 1926 Subpart AA, sets out what has to happen before anyone enters one on a construction site.
Is it permit-required?
A confined space is large enough to enter, not designed for continuous occupancy, and has limited entry or exit. It becomes a permit-required confined space if it also has a hazardous atmosphere, engulfment potential, an inwardly converging shape, or any other serious hazard. Manholes, tanks, sewers, pits and some crawl spaces commonly qualify.
Before entry
The employer must identify confined spaces, and for permit-required ones: test and monitor the atmosphere, issue an entry permit, provide an attendant outside, establish communication, and have rescue arranged before entry — not improvised afterward. Continuous atmospheric monitoring is standard.
Coordinate on multi-employer sites
Subpart AA specifically requires the controlling contractor to coordinate entry operations when more than one employer is involved — so information about the space and its hazards is shared, not lost between crews.
Questions, answered
What makes a confined space 'permit-required'?
A confined space becomes permit-required if it contains or could contain a hazardous atmosphere, engulfment potential, an inwardly converging configuration, or any other recognized serious safety or health hazard.
Do I need a rescue plan before entry?
Yes. For permit-required confined spaces, rescue arrangements must be in place before entry begins. Relying on calling 911 after something goes wrong does not meet the standard.
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