Part 113 min

1.3 1910.146 and 1926 Subpart AA, side by side

There are two confined space standards, and which one you are under changes real things: who has to find the spaces, whether monitoring is continuous, whether a permit can be suspended instead of cancelled, and who owes information to whom on a site with four contractors on it. General industry has had 29 CFR 1910.146 since 1993. Construction got 29 CFR 1926 Subpart AA in 2015, and it is a noticeably tighter document.

1 What construction had before 2015, and what it has now

Before Subpart AA, a construction employer's confined space obligations rested on the general training duty of 29 CFR 1926.21(b) and on the general duty clause — a paragraph of instruction, not a program. The 2015 rule, published at 80 FR 25366 on May 4, 2015, added eleven sections that map closely onto 1910.146 without being a copy of it, and amended 1926.21 at the same time (the amendment appears in that section's own citation line, 80 FR 25518). If you find an old training deck citing a confined space paragraph inside 1926.21, check the current text before repeating the number: the paragraph a pre-2015 document points at is not necessarily there any more.

The scope section is worth reading for its own sake. 1926.1201(a) carries a note listing where confined spaces occur in construction, and the list is longer than most site assessments: bins; boilers; pits such as elevator, escalator, pump and valve pits; manholes of every utility; tanks; incinerators; scrubbers; concrete pier columns; sewers; transformer vaults; HVAC ducts; storm drains; water mains; precast manhole units; drilled shafts; enclosed beams; vessels; digesters; lift stations; cesspools; silos; air receivers; sludge gates; air preheaters; step-up transformers; turbines; chillers; bag houses; and mixers or reactors.

On the job: use that list as a walk-down sheet. It is public-domain regulatory text, it is specific to construction, and it names the spaces — concrete pier columns, drilled shafts, enclosed beams — that a general industry checklist never thinks to mention.

2 Three exceptions, and the trench question

1926.1201(b) takes three kinds of work out of Subpart AA: construction work regulated by Subpart P (Excavations), by Subpart S (Underground Construction, Caissons, Cofferdams and Compressed Air), and by Subpart Y (Diving). So a trench is not a Subpart AA problem — its atmosphere is handled by 1926.651(g), which requires testing before employees enter excavations greater than 4 feet deep wherever oxygen deficiency or a hazardous atmosphere exists or could reasonably be expected.

What Subpart AA does cover is the manhole, the vault, the wet well or the pipe that gets opened inside the excavation. Work in that space is not work regulated by Subpart P. And 1926.1201(c) closes the gap in general terms: where this standard applies and another applicable OSHA standard addresses a confined space hazard, the employer must comply with both.

3 The differences that change what you do

29 CFR 1910.146 and 29 CFR 1926 Subpart AA, on the points that differ
Question	General industry — 1910.146	Construction — 1926 Subpart AA
Who identifies the spaces, and when?	The employer evaluates the workplace — (c)(1)	A competent person, before work begins at the site, including testing as necessary — 1926.1203(a)
Monitoring during entry	Test or monitor as necessary to determine that acceptable conditions are maintained — (d)(5)(ii)	Continuous monitoring, unless the employer demonstrates that continuous equipment is not commercially available or that periodic monitoring is frequent enough — 1926.1204(e)(2)
Engulfment that cannot be isolated	No specific provision	An early-warning system that continuously monitors and alerts entrants and attendants in time to exit — 1926.1204(e)(1)(iii)
If a prohibited condition arises	The entry supervisor terminates entry and cancels the permit — (e)(5)(ii)	Cancel, or suspend and fully reassess the space before reentry where the condition is temporary and creates no new hazard — 1926.1205(e)(2)
Ventilation failure	Covered through the acceptable entry conditions	The permit must state the means of detecting an increase in atmospheric hazard levels if the ventilation system stops working — 1926.1206(e)
Language of the training	Not addressed	In a language and vocabulary the employee can understand — 1926.1207(b)(1)
Rescue awareness	Covered through (d)(9)	Training must give employees not authorized to perform entry rescues an understanding of the dangers of attempting one — 1926.1207(a)
Rescue service availability	Evaluate, select, inform, give access — (k)(1)	Same, plus the service must agree to notify the employer immediately if it becomes unavailable — 1926.1211(a)(3)(iii)
Non-entry rescue	A retrieval system is used unless it would increase risk or not contribute — (k)(3)	Stated as a duty: non-entry rescue is required unless one of those two applies; otherwise designate an entry rescue service — 1926.1211(c)
Training records	Certification with each employee's name, trainers' signatures or initials and the dates — (g)(4)	Records with each employee's name, the trainers' names and the dates, kept for the period of employment — 1926.1207(d)
Lighting inside the space	Enough to work safely and exit quickly — (d)(4)(v)	Same, plus meeting the illumination minimums of 1926.56 and approved for the ignitable or combustible properties of what is present — 1926.1204(d)(5)

4 Four employers, one hole in the ground

The biggest structural difference is that Subpart AA assumes a multi-employer site and names the parties. 1926.1202 defines them:

1
Host employer — the employer that owns or manages the property where the construction work is taking place. There is never more than one host employer on a site.
2
Controlling contractor — the employer with overall responsibility for construction at the site. It is the primary point of contact for information about permit spaces.
3
Entry employer — any employer who decides that an employee it directs will enter a permit space. Every subcontractor sending people in is an entry employer, and each one owes its own program.

1926.1203(h) then sets out the information flow, and it runs in both directions. Before entry operations begin the host employer gives the controlling contractor the location of each known permit space, the hazards or the reason each is a permit space, and any precautions previously implemented. The controlling contractor passes that on to every entity that will enter and to any other entity whose activities could foreseeably create a hazard in the space. Each entry employer obtains that information and tells the controlling contractor what program it will follow and what hazards it is likely to confront or create.

Then, after the work: 1926.1203(h)(5) requires the controlling contractor to debrief each entity that entered, each entry employer to report the program it followed and the hazards it met or created, and the controlling contractor to pass that back to the host employer. If there is no controlling contractor on site, 1926.1203(i) puts the role onto the host employer or whoever arranged the work.

Common mistake: the coordination duty of 1926.1203(h)(4) is not only about two crews entering at once. It also covers entry happening at the same time as any activity that could foreseeably create a hazard in the space — a paving crew running a compactor over the vault lid, a mechanic starting a generator near the only opening, a plumber charging a line that discharges into the space. Nobody in those examples is entering anything.

5 Host and contractor duties in general industry

1910.146 has the same idea in a shorter form. Under (c)(8) a host employer that arranges for a contractor to perform permit space entry must inform the contractor that the workplace contains permit spaces and that entry is allowed only under a compliant program; apprise it of the elements that make the space a permit space, including the host's own experience with it; apprise it of any precautions the host has implemented; coordinate entry operations when both host and contractor personnel will be working in or near the space; and debrief the contractor afterwards about the program followed and any hazards confronted or created.

Under (c)(9) the contractor has the mirror-image duties: obtain the available information from the host, coordinate, and inform the host of the program it will follow and any hazards it met or created — through a debriefing or during the entry itself.

The phrase to notice in both standards is “the host employer's experience with the space.” That is institutional memory: the vault that always reads low on oxygen after rain, the tank that off-gasses when the sun hits it, the line that somebody once found still charged. None of it is in the drawings, and a contractor cannot discover it by looking.

6 What is identical, and worth memorizing once

The core is the same in both standards, and the numbers are the same numbers:

The three conditions of a confined space, and the four characteristics of a permit space — 1910.146(b), 1926.1202.
Oxygen below 19.5 percent or above 23.5 percent, flammables above 10 percent of the LFL.
The order of tests: oxygen, then combustible gases and vapors, then toxics — 1910.146(d)(5)(iii), 1926.1204(e)(3).
At least one attendant outside for the duration of entry operations — 1910.146(d)(6), 1926.1204(f).
A mechanical device available for retrieval from vertical spaces more than 5 feet deep — 1910.146(k)(3)(ii), 1926.1211(c)(2).
Cancelled permits retained at least one year, and the program reviewed within one year of each entry — 1910.146(e)(6) and (d)(14), 1926.1205(f) and 1926.1204(n).
Rescuers practice on actual or representative spaces at least once every 12 months — 1910.146(k)(2)(iv), 1926.1211(b)(4).

Everything else in this course names its standard as it goes. When a paragraph is quoted with a 1910 number, it is general industry; a 1926 number is construction. Where they agree, both are given.

Key takeaways

1910.146 covers general industry; 1926 Subpart AA has covered construction since 2015 and does not apply to work regulated by Subpart P (excavations), Subpart S or Subpart Y — 1926.1201(b).
Construction requires a competent person to identify every confined space and permit space before work begins — 1926.1203(a).
Construction makes continuous atmospheric monitoring the default and adds an early-warning system for non-isolated engulfment hazards — 1926.1204(e).
Construction lets a permit be suspended and the space reassessed for a temporary condition that creates no new hazard; general industry only cancels — 1926.1205(e)(2) vs 1910.146(e)(5)(ii).
Subpart AA names the host employer, the controlling contractor and each entry employer, and routes information through the controlling contractor before and after entry — 1926.1203(h).
General industry has the same idea in (c)(8) and (c)(9), including the host's duty to share its own experience with the space and to debrief the contractor afterwards.

Free educational content — not OSHA-authorized training, no certificate or card issued. Follow your employer's program and the standards cited.