Permit-required confined space
A confined space with at least one serious hazard, such as a possible hazardous atmosphere, engulfment or entrapment.
Definition, in the source's words
29 CFR 1910.146(b)(opens ecfr.gov in a new tab)“Permit-required confined space (permit space) means a confined space that has one or more of the following characteristics: (1) Contains or has a potential to contain a hazardous atmosphere; (2) Contains a material that has the potential for engulfing an entrant; (3) Has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward and tapers to a smaller cross- section; or (4) Contains any other recognized serious safety or health hazard.”
What it means
It's a confined space first, then any one of four characteristics makes it a permit space. Note the word potential in (1): the atmosphere doesn't have to be hazardous right now.
Entering a permit space brings in the written program, entry permits, an attendant, an entry supervisor and rescue arrangements under 1910.146.
Example
A sewer lift station wet well can collect hydrogen sulfide. Even if today's reading is clean, it has the potential to contain a hazardous atmosphere, so characteristic (1) applies and it's a permit space. A grain bin meets (2) because the grain can engulf an entrant.
Where it appears on the exam
ASP: ASP11 Domain 2, Safety Programs and Concepts
Practice: Permit-Required Confined Spaces
CSP: CSP11 Domain 1, Advanced Application of Safety Principles
Practice: Confined Spaces and Lockout/Tagout
CHST: CHST5 Domain 1, Hazard and Risk Identification and Control
Practice: Confined Spaces in Construction
Questions
- Does a permit space need all four characteristics?
- No. One or more of the four is enough.
Related
- Confined space
- Hazardous atmosphere
- Attendant (confined space)
- Entry supervisor
- IDLH (immediately dangerous to life or health)
- Regulation: 29 CFR 1910.146
Checked 2026-10-16. Spot a problem? Email hello@passcited.com.