1.1 What a confined space actually is
Ask a crew to point at the confined spaces on their site and they will point at manholes. Ask them about the crawl space under the mechanical room, the pit under the conveyor, the inside of the new duct run, the water tank on the roof, and the answers get vaguer. That is the whole problem: a confined space is defined by three conditions in 29 CFR 1910.146(b), and none of them is “looks like a manhole.”
1 Three conditions, and all three at once
1910.146(b) defines a confined space as a space that meets all three of the following. 29 CFR 1926.1202, the construction definition, is worded identically. Miss one condition and the space is not confined; meet all three and it is, whatever it is called on the drawings.
Notice what is not in the definition. There is no minimum or maximum volume. There is no list of shapes. There is nothing about depth, nothing about whether the space is underground, and nothing about whether it holds a hazard — hazards are the next question, the one that decides whether the space is permit-required. The first question is only about geometry and purpose.
2 “Large enough and so configured that an employee can bodily enter it”
This condition rules out the spaces you can only reach into. A hopper you clear with a rod, a chute you unjam with a bar, a machine cabinet you put an arm inside — none of those is a confined space, because a body cannot get in. The moment the space is big enough that somebody could climb in and work, it clears this hurdle, and it does not matter whether anyone intends to.
The word to hold on to is bodily. It is the same idea that governs the definition of entry at 1910.146(b): entry is the action by which a person passes through an opening into a permit-required confined space, it includes the work that follows, and it “is considered to have occurred as soon as any part of the entrant's body breaks the plane of an opening into the space.” The construction version at 1926.1202 adds five words that settle a lot of arguments: whether or not such action is intentional or any work activities are actually performed in the space.
3 “Limited or restricted means for entry and exit”
People read this as a statement about the size of the opening. It is really a statement about getting out. A 30-inch manhole is a limited means of exit even though a person fits through it easily, because a person who is dizzy, or who is trying to climb a fixed ladder while carrying a wrench, or who has to be lifted out by somebody else, cannot use it the way they would use a door.
Restricted means of exit shows up in shapes that have no small opening at all. A tank with a hatch on the roof and a 20-foot drop to the floor has a large opening and a badly restricted exit. A pit with a fixed ladder, an open-topped vessel you get into over the rim, a vault entered through a floor plate, a duct that runs 40 feet to the next access panel: all restricted, none of them because the hole was small.
The practical test on the floor: if the person inside collapsed, could they get themselves out? If the answer needs equipment, a second person, or a rope, the means of exit is restricted.
4 “Not designed for continuous employee occupancy”
This is the condition that decides most disputes, and it is a question about the designer's intent, not about the current use. A control room is designed for people: it has lighting, ventilation, an exit route and a floor to stand on. A digester is designed to hold sludge. Someone working inside the digester is a temporary visitor in a space built for something else, and everything that makes a workplace survivable — air changes, exits, light — has to be brought in and maintained by the crew.
A common mistake runs the other way: assuming a space is fine because people are in there all the time. A crawl space under a building that the maintenance crew visits weekly is still not designed for occupancy. Frequency of use is not evidence of design.
5 The spaces that get missed
The list below is not in the standard — the standard gives no list, which is exactly why the definitions matter. What it does contain is the kind of space that turns up in incident reports because nobody had classified it.
| Space | Which condition people forget |
|---|---|
| Electrical or utility vault under a sidewalk or roadway | Not designed for occupancy; exit is a floor plate and a ladder. The vault in Summary Nr 146892.015, where two workers died, was one of these. |
| Elevator or escalator pit | Restricted exit, and it is full of energy sources rather than bad air — Summary Nr 142862.015 (01/19/2022): an employee working inside an escalator pit was pulled in and crushed when the escalator energized while a coworker tested electrically at the bottom. |
| Tank trailer, tanker truck, rail car | Everyone sees the small hatch; fewer see that residue makes the atmosphere — Summary Nr 144331.015 (03/07/2022): a worker inspecting a semi tank trailer collapsed, apparently from overexposure to sodium hypochlorite. |
| Crawl space, attic plenum, pipe chase | Frequency of visits mistaken for design intent |
| New ductwork or new pipe, before commissioning | Nobody thinks of it as a space at all until somebody is inside it welding |
| Open-topped pit, sump, wet well, boiler, kiln, hopper, bin, silo | Open top read as “not confined” — but the exit is still restricted and the space was never designed for people |
| A manhole or vault opened inside a trench | The trench has its own standard, 1926 Subpart P; the manhole in the trench floor is a separate confined space with its own rules |
6 Who has to find them, and by when
In general industry the duty is 1910.146(c)(1): the employer shall evaluate the workplace to determine if any spaces are permit-required confined spaces. The note to that paragraph points at the decision flow chart in Appendix A, which walks the same questions this chapter has walked.
Construction is more specific, and the timing is tighter. 1926.1203(a): before it begins work at a worksite, each employer must ensure that a competent person identifies all confined spaces in which one or more of the employees it directs may work, and identifies each space that is a permit space, through consideration and evaluation of the elements of that space, including testing as necessary. A competent person, defined at 1926.1202, is someone capable of identifying existing and predictable hazards and authorized to take prompt corrective measures to eliminate them. Both halves matter: identification without authority is a report, not a control.
Once a permit space is identified, 1910.146(c)(2) and 1926.1203(b)(1) require exposed employees to be informed by posting danger signs or by any other equally effective means. Both standards offer the same sample wording: DANGER — PERMIT-REQUIRED CONFINED SPACE, DO NOT ENTER. Construction adds a second obligation at 1926.1203(b)(2): inform employees' authorized representatives and the controlling contractor, in a timely manner, by some means other than posting. A sign talks to the person standing in front of it; the controlling contractor needs a phone call.
7 If you decide nobody will go in
That is a legitimate answer, and it is not a free pass. 1910.146(c)(3): if the employer decides its employees will not enter permit spaces, it must take effective measures to prevent them from entering, and it still has to comply with (c)(1) evaluation, (c)(2) signs, (c)(8) host-employer duties toward contractors and (c)(8)'s companion paragraphs. 1926.1203(c) says the same for construction: effective measures to keep the directed employees out, plus all other applicable requirements.
“Effective measures” means something physical or procedural, not a policy nobody has read. A bolted cover, a locked hatch, a barricade with signage, a written prohibition that supervisors enforce. It is the same standard of proof as anywhere else in the standard: you should be able to walk someone to the space and show them what stops entry.
- A confined space meets three conditions at once: a person can bodily enter it, entry and exit are limited or restricted, and it was not designed for continuous employee occupancy — 1910.146(b), 1926.1202.
- None of the three conditions mentions a hazard. Hazards decide whether the space is permit-required, which is the next chapter.
- “Restricted means of exit” is about getting out under stress, not about the width of the opening. An open-topped tank 20 ft deep qualifies.
- Entry has occurred as soon as any part of the body breaks the plane of the opening — intentionally or not, and whether or not any work is done (1910.146(b), 1926.1202).
- General industry: the employer evaluates the workplace, 1910.146(c)(1). Construction: a competent person identifies every confined space and every permit space before work begins, 1926.1203(a).
- Deciding that nobody will enter still requires effective measures to prevent entry, plus the evaluation, the signs and the contractor duties — 1910.146(c)(3), 1926.1203(c).
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