Confined Spaces

A confined space is any enclosed or partially enclosed space with restricted entry or exit that is not designed or intended for continuous human occupancy. The word ‘confined’ may suggest ‘small’, but not all confined spaces are. Some examples of confined spaces include tanks, access shafts, utility vaults, sewers, pipes, truck or rail tank cars, boilers, manholes, silos, and storage tanks. Ditches and trenches may also be a confined space when access or egress is limited.

A space must meet all of the following criteria to be considered a confined space:

  • A space that is large enough to bodily enter.
  • A space that has limited means of entry or exit.
  • A space not designed for continuous employee occupancy.


Many confined spaces contain hazardous substances or dangerous conditions. Hazards and threats could include:

  • Poor Air Quality
    • Atmospheres with an oxygen content less than 19.5% (deficient) or more than 23% (enriched) are not safe.
  • Toxic Gasses
    • Hydrogen sulfide, carbon dioxide, carbon monoxide, smoke, ammonia, chlorine, etc. are all potentially deadly.
  • Flammable Atmospheres
    • A highly explosive atmosphere can be created when finely ground combustible materials such as grain, carbon, cellulose, fibers, plastics, or flammable liquids are present.
  • Mechanical, Electrical, or Physical Hazards
    • Examples include moving parts, structural hazards, noise, temperature, and visibility.
  • Loose Materials that may Engulf or Smother
    • Shifting or collapse of bulk material, barrier failures, etc.

A NON-PERMIT CONFINED SPACE is a confined space which contains secondary hazards (i.e., slips, falls, poor lighting, etc.) which are not anticipated to cause death or serious physical harm under normal operating conditions. Non-permit Spaces do not contain a hazardous atmosphere or have the potential to contain a hazardous atmosphere under normal condition.

Examples of Non-Permit Confined Spaces Include:

  • Air Handling Units
  • Plenum Spaces
  • Attic Spaces

A PERMIT-REQUIRED CONFINED SPACE is a Confined Space, which has one or more of the following characteristics:

  • Contains or has the potential to contain a hazardous atmosphere.
  • Contains a material that has the potential for engulfing an Entrant.
  • Has an internal configuration that may cause an employee to become trapped, or asphyxiated by inwardly  converging walls or a tapering floor.
  • Contains any other recognized serious safety or health hazards.

Examples of Permit-Required Confined Spaces Include:

  • Sewer Ejector Pits
  • Condensate Pits
  • Tanks
  • Boilers
  • Crawl Spaces
  • Manholes