Confined Space Classification

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Regardless of the classification level of confined space, an employer may decide that its employees will never enter permit spaces."

A Guide to Classifying Your Confined Spaces

Confined spaces can be found in almost any type of industry or workplace. Being able to identify and classify confined spaces present in the workplace will not only make it easier to maintain a written confined space program, but also help ensure the safety of workers who will be working in these confined spaces. A confined space is defined by OSHA as having these 3 characteristics:

  • Having limited means for entry and exit
  • Being large enough for continuous human occupancy
  • Not designed for continuous human occupancy

Confined space classification levels can affect the safety of workers. Confined Space Classification Levels

Confined spaces can then be further categorized into different classification levels. The different classification levels of confined space have important differences that can affect the safety of workers. The classification levels are as follows:

Non-Permit Confined Space

By OSHA’s definition in CFR 1910.146, a non-permit confined space means “a confined space that does not contain or, with respect to atmospheric hazards, have the potential to contain any hazard capable of causing death or serious physical harm.”

  • It is critical to ensure that when a confined space is classified as a non-permit space, that all potential for health or safety hazards have been completely eliminated. The following conditions must be met:
  • The confined space contains no potential or existing hazardous atmosphere
  • The confined space does not contain hazards capable of causing physical harm or fatality. This includes, but is not limited to, electrical shock, hazards of moving components, or engulfment in liquid or solid material.
  • It is important to note that if a confined space must be entered to remove the existing hazards, the space is treated as a permit-required confined space until all hazards are eliminated.
  • Documentation must be provided on how the confined space was determined to be a non-permit confined space.

Permit-Required Confined Space

By OSHA’s definition in CFR 1910.146, a permit-required confined space means “a confined space that has one or more of the following characteristics:

  • Contains or has a potential to contain a hazardous atmosphere;
  • Contains a material that has the potential for engulfing an entrant;
  • 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
  • Contains any other recognized serious safety or health hazard.”
  • A confined space deemed as permit-required may pose health or safety hazards, and require a permit for entry.
  • Once a confined space has been identified as permit-required, the employer should provide signage or some other form of effective communication to let others know of the existing confined space.
  • Before an authorizer employee can enter a permit-required confined space, a written or printed permit must be provided by the employer to allow entry into the confined space.

There are many different types of spaces that fall under confined space classification. Do Not Enter Confined Space

Regardless of the classification level of confined space, an employer may decide that its employees will never enter permit spaces. To properly implement this, the employee has to ensure that effective measures are taken to prevent workers from entering permit spaces, such as adequate signage or any other equivalent means.

Reclassification of Confined Spaces

Under certain conditions and requirements, a non-permit confined space can be reclassified as a permit-required confined space, or vice versa. If changes are made to non-permit confined space where hazards develop or are re-introduced, it must be reclassified as a permit-required confined space. Similarly, if all hazards in a permit-required confined space can be completely eliminated without entry and are no longer present, it can be reclassified as a non-permit confined space.

Common Types of Confined Spaces

  • HVAC ducts: Non-permit CS
  • Air handler units and elevator pits
  • De-energized and lockout/tagout performed: Non-permit CS
  • Not de-energized: Permit-required CS
  • Telecommunication manholes: Non-permit CS
  • Electrical manholes and manholes containing water or sewage
  • Oxygen or hazardous gases reduced to below hazardous levels: Non-permit CS
  • Not de-energized or lockout/tagout not performed: Permit-required CS
  • Storage tanks and silos: Permit-required CS
  • Hoppers with auger: Permit-required CS


Confined space operations are one of the leading causes for occupation fatalities in the United States. Having the preparation and knowledge, as well as being able to properly identify the hazards associated with confined space and classifying confined spaces properly can greatly reduce the risk of these dangers. Contact us to better understand confined space classification.

About Kristopher Carreon
Kristopher Carreon has managed multiple lockout/tagout implementation projects for many large companies in the US and Internationally. He has worked in various industries including manufacturing, automotive, lumber, mining, and railroad. Kris specializes in mining facilities and has a clear understanding of what is needed for the clients to meet their MSHA regulations.