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Confined Spaces Overview

Learning Objectives

  • Identify characteristics and examples of a confined space
  • Identify hazards of confined spaces
  • Identify the differences between permit-required and non-permit-required confined spaces

Available in English, Spanish

This lesson educates all general industry employees about the existence of confined spaces, the type of hazardous conditions that can be present in them, and the basic requirements for entry into permit-required confined spaces.

Confined spaces - such as manholes, crawl spaces, and tanks - are not designed for continuous occupancy and are difficult to exit in the event of an emergency. People working in confined spaces face life-threatening hazards including toxic substances, electrocutions, explosions, and asphyxiation.

Confined spaces are enclosed or partially enclosed spaces of a size such that a worker can squeeze entry for performing assigned work through a narrow opening—they’re tough to get in and out of, tight spaces. These spaces are normally only entered to perform specific tasks and then barricaded to prevent unauthorized access.

Many confined spaces are also poorly ventilated, so the release of vapors which might otherwise be released into the open air can create an oxygen-deficient, toxic, combustible, or otherwise harmful atmosphere.  Exposure to these atmospheres can result in immediate asphyxiation, acute or chronic poisoning, or impairment that can result in injury. Asphyxiation is the leading cause of death in confined spaces. Confined spaces can also pose the hazard of asphyxiation or other injury from engulfment in the materials within the space, such as grain or sawdust within a silo.  

Confined spaces kill when several unexpected situations develop.

Oxygen deficiency is one probable factor contributing to confined space accidents. This is when the air in a confined space is consumed by chemical or biological reactions, diluting the percentage of oxygen in the immediate atmosphere to below 21%, causing increasingly negative physiological responses as that percentage declines.

Oxygen displacement is another killer in confined spaces. Typically, this is when inert gas is present at levels that remove oxygen from the chamber, essentially crowding out the normal air we breathe and replacing it with, say colorless, odorless gases like nitrogen or carbon dioxide, creating a situation of complete suffocation for workers.

Regulations
  • OSHA Act Section 5(a)(1), known as the General Duty Clause
  • 29CFR 1910.146 Permit-required confined spaces
  • Appendix A to 1910.146 -- Permit-Required Confined Space Decision Flow Chart
  • Procedures for Atmospheric Testing - 1910.146 App B
  • Examples of Permit-Required Confined Space Programs - 1910.146 App C
  • Confined Space Pre-Entry Check List - 1910.146 App D
  • Sewer System Entry - 1910.146 App E
  • Non-Mandatory Appendix F -- Rescue Team or Rescue Service Evaluation Criteria - 1910.146 App F