TL;DR
- Construction has its own confined space standard (29 CFR 1926 Subpart AA), effective 2015 — separate from 1910.146, which most safety managers know but does not apply to construction.
- Any space large enough to enter, not designed for continuous occupancy, and with limited means of entry or exit is a confined space. Add a recognized hazard and it becomes permit-required.
- Every permit-required entry needs a written permit, a designated entry supervisor, a trained attendant who stays outside, and a pre-planned rescue procedure.
- On multi-employer sites, the host, controlling contractor, and entry employer each have defined coordination duties — failure at any level is citable.
- Atmospheric testing must happen before entry and continuously during: oxygen first, flammable gas second, toxic contaminants third.
Two workers die in confined spaces every week in the United States. Most of those deaths are preventable, and a significant number involve would-be rescuers who entered without proper equipment and died alongside the original victim. Confined space entry is one of the few areas where the cure kills as often as the hazard itself.
OSHA's construction-specific confined space rule, 29 CFR 1926 Subpart AA, took effect August 3, 2015. It replaced a patchwork of general industry provisions that construction employers had been incorrectly applying for years. If your safety program still references 29 CFR 1910.146 for construction confined space work, it needs to be updated.
What Counts as a Confined Space
A confined space has three characteristics:
- Large enough for an employee to enter and perform assigned work
- Limited or restricted means of entry or exit
- Not designed for continuous employee occupancy
Excavations, manholes, crawl spaces, tanks, silos, vaults, utility tunnels, and pits typically meet this definition on construction sites. The physical characteristics matter more than the label. A trench that workers enter to perform work is a confined space.
Permit-Required vs. Non-Permit
A confined space becomes permit-required if it has one or more of the following:
- Contains or has a potential to contain a serious atmospheric hazard — oxygen deficiency or enrichment, flammable gases above 10% of the lower explosive limit (LEL), or airborne contaminants at or above permissible exposure limits
- Contains material with the potential for engulfment — grain, sand, liquid, or any flowable solid that could trap or suffocate a person
- Has an internal configuration that could trap or asphyxiate — inwardly converging walls, a floor that slopes downward, any geometry where a worker could be trapped
- Contains any other recognized serious safety or health hazard
Non-permit spaces still require evaluation and monitoring. If conditions change to create a hazard, the space becomes permit-required immediately.
Multi-Employer Coordination
This is where 1926 Subpart AA differs most from the general industry rule, and where construction sites most commonly fail. Three distinct roles must be coordinated when multiple employers are involved — which on most construction sites means always.
Host employer: The entity that owns or manages the facility. Before any confined space work begins, the host must identify all confined spaces, communicate their locations, and provide all known hazard information to the controlling contractor.
Controlling contractor: Typically the GC. Must coordinate between the host and any entry employers, ensure entry employers have the information they need, and share hazard information when multiple subs work near the same space.
Entry employer: The employer whose workers actually enter the space. Responsible for the permit system, atmospheric testing, attendant, and rescue.
OSHA citations from confined space incidents frequently cite all three employers. Not knowing about a space is not a defense for a controlling contractor who failed to ask.
The Entry Permit
A written entry permit must be completed before anyone enters a permit-required space. A compliant permit must include:
- The space being entered and the purpose of the work
- Date and authorized duration of entry
- Authorized entrants and entry supervisor
- Hazards identified in the space
- Measures to isolate and control hazards — lockout/tagout, blanking, purging
- Acceptable entry conditions with specific thresholds: oxygen %, LEL %, PEL %
- Atmospheric testing results — tester name and time of each reading
- Communications procedures between entrants and attendant
- Required equipment: respirators, retrieval systems, communications
- Rescue and emergency services and how to reach them
Permits must be retained for one year after entry.
The Three Roles
Every permit-required entry requires three designated roles. Consolidating them is where fatalities happen.
Entry supervisor: Authorizes entry, verifies conditions are acceptable, confirms required equipment is present and working, verifies rescue service availability, and signs the permit. May also serve as the attendant — but cannot be an authorized entrant.
Authorized entrant: The worker entering the space. Must know the hazards, recognize signs and symptoms of exposure, use equipment correctly, maintain communication with the attendant, and exit immediately if directed or if conditions change.
Attendant: Remains outside the space at all times. Tracks authorized entrants. Monitors conditions inside and outside the space. Maintains continuous communication with entrants. Summons rescue if needed. Does not enter the space to rescue an entrant — calls for trained rescue instead. The attendant has one job. No production work.
Atmospheric Testing
Testing must occur before entry and continuously during entry for permit-required spaces. The sequence matters:
- Oxygen first: Below 19.5% is oxygen-deficient and requires supplied-air respiratory protection. Above 23.5% is oxygen-enriched and creates a fire hazard.
- Flammable gases second: Above 10% LEL triggers action. Above 25% LEL requires evacuation.
- Toxic contaminants third: Based on what the space previously contained, what work is being done, and what adjacent operations could introduce.
Testing must be performed by someone trained on the equipment. Readings must be documented on the permit. Calibration records for the atmospheric monitor must be maintained.
Rescue Requirements
Rescue planning happens before entry, not after something goes wrong.
Non-entry rescue is preferred and is required for vertical entries deeper than 5 feet in most conditions. A chest or full-body harness with a retrieval line attached to a mechanical retrieval device — tripod or davit arm — at the entry point allows rescuers to extract a worker without entering the space.
Entry rescue is used where retrieval is not feasible. This requires either an on-site trained rescue team or an emergency response service that has been informed of the confined space hazards and can respond.
Many confined space fatalities are rescuers. A worker becomes incapacitated and coworkers who are untrained and unequipped attempt a rescue. The result is frequently multiple deaths in the same space. Everyone involved must know the rescue plan before entry begins.