What is a confined space?

A confined space is some place (like an underground vault or storage tank) that is not designed for continuous human occupancy, is large enough to fit the whole body inside of, and has restricted means of egress.

What is a permit-required confined space?

A permit-required confined space meets at least one of four additional criteria in addition to those explained above.

  1. The space has the potential to contain a hazardous atmosphere. This includes oxygen deficiency, toxic gases, and flammable vapors.

  2. The space poses an engulfment hazard. This is the potential to become engulfed by some material, whether it be a solid or liquid.

  3. An internal configuration with inwardly converging or sloping walls that could crush and asphyxiate a person.

  4. Any other serious hazard that would endanger life. This can be heat, electricity, or some mechanical means like fan blades.

If a space meets all of the first three requirements and at least one of the second four, the space requires special procedures before any employee may enter.

How do I recognize a permit-required confined space?

At the Laboratory, any space that has been recognized by the Safety Division as a permit-required confined space will be labeled with this sign.
If you don't see this sign, but are suspicious about the safety of the space, please contact the Safety Division, who will perform an analysis and determine if the space is a permit-required confined space. Keep the guidelines that are outlined above for identifying a confined space in mind when working in any area that may be enclosed or pose access concerns.

Can I work in a permit-required confined space?

Permit-required confined spaces can be exceptionally dangerous. Only individuals who have been appropriately trained and who have received a confined space entry permit from the Safety Division may enter a permit-required confined space. The training is administered as a class by a representative of the Safety Division. You should contact Training to sign up for the next class.

Requirements for Working In a Permit Required Confined Space

There are 3 basic requirements: Confined Space Entry Training, a Confined Space Entry Permit, and a Safety Watch. Other requirements will be specified on the Confined Space Entry Permit.

Confined Space Entry Training

  • Requires renewal every 2 years.
  • Must attend an instructor-led training session every other period, or once every 4 years.
  • All entrants, safety watches and responsible persons must have this training.

Confined Space Entry Permit

  • Written by Industrial Hygienist (IH) of ES&H. Contact Bill Slavin or Neil Gerrish for a permit.
  • Permits are written for the duration of a job.
  • Maximum duration for a standard permit is 30 days. There are a few routine permits with a 6 month duration.
  • Signed by IH, initialed by Responsible Person
  • Permit is posted at location of Permit-Required Confined Space
  • All requirements listed on permit must be carried out. Responsible person initials permit for each requirement when completed.
  • All requirements must be completed and initialed BEFORE entry into the confined space may begin.
  • Upon completion of work, the permit must be canceled and returned to IH by the Responsible Person.

Safety Watch

  • Referred to as attendant by OSHA
  • Main job is to maintain constant contact with the entrants.
  • May NEVER enter a confined space while acting as Safety Watch.

Non-Permit Confined Spaces

A confined space as defined above that has no potential for atmospheric hazard, and no potential for causing death or serious harm.
  • A large empty cardboard box may meet the definition of a confined space, but poses no hazards.
  • There are no requirements for working in a non-permit confined space beyond normal work practices.
  • Note: If you add a serious hazard to a non-permit confined space, it becomes a permit-required confined space.
    • Example, welding in a large empty cardboard box would be hazardous enough to make it permit-required.


ESHD 5008, Section 8 "Industrial Hygiene", Chapter 5 "Confined Spaces"