What is a confined space?
A confined space is a space large enough for a person to enter and work in, with limited or restricted ways in and out, that is not designed for someone to stay in.
Also called permit-required confined space, permit space
What it means.
That is OSHA's three-part test in 29 CFR 1910.146(b). Tanks, vessels, silos, storage bins, hoppers, vaults and pits are among the examples the rule gives.
A permit-required confined space is a confined space that also has one or more serious hazards: a hazardous atmosphere or the potential for one, a material that could engulf a person, an inside shape that could trap or asphyxiate someone (inwardly converging walls, or a floor that slopes downward and tapers to a smaller cross-section), or any other recognized serious safety or health hazard. Entry into a permit space is controlled by a written entry permit, and the employer must evaluate the workplace to find out whether any permit spaces exist.
Not every confined space is permit-required, and not every hole in the ground is a confined space. Getting the classification right is most of the work.
Entry permit (permit) means the written or printed document that is provided by the employer to allow and control entry into a permit space
Where it shows up on a job.
Cleaning out a hopper, inspecting a vault or repairing the inside of a tank. Before anyone goes in, the site confirms whether the space is permit-required and, if it is, completes the entry permit with the people entering, the attendant and the conditions that must hold for entry.
Where this comes from.
Each source was read on 22 October 2026. Guidance is advice; a regulation is the rule.
- 29 CFR 1910.146Code of Federal Regulations, Title 29. Regulation. Confined space, permit space, entry permit and hot work permit definitions.
- Confined SpacesOccupational Safety and Health Administration. OSHA guidance, advisory. OSHA's overview of the confined space standards.
A plain-language definition, not legal advice. For a decision on your site, read the standard that applies to it.
Related terms
- permit to work
A permit to work is a written authorization, signed by someone allowed to sign it, for a specific hazardous job to go ahead under named controls for a set period.
- hot work
Hot work is any job that can start a fire because it is a source of ignition, such as welding, cutting, burning, heating or riveting.
- lockout/tagout
Lockout/tagout is putting a lock, a tag or both on the device that controls a machine's energy, so the machine cannot start or release stored energy while someone works on it.
- job hazard analysis
A job hazard analysis is breaking a job into steps, identifying what could go wrong at each step, and deciding how to control it before the work starts.
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