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Confined Space Hazards 101: The Basics

03 February, 2023

A confined space consists of any one of the following characteristics:

  • Limited openings for entry and exit
  • Unfavorable natural ventilation
  • Not designed for continuous worker occupancy

Examples of confined spaces include, but are not limited to:

  • Storage tanks
  • Silos
  • Pits
  • Vats
  • Compartments of ships
  • Process vessels
  • Degreasers
  • Reaction vessels
  • Furnaces, incinerators, boilers and steam drums
  • Ventilation and exhaust ducts
  • Sewers
  • Tunnels
  • Underground utility vaults
  • Pipes
  • Includes construction confined spaces as of March 2015
    • Isolated-Hazard Confined Space
    • Controlled-Atmosphere Confined Space
    • Permit-Required Confined Space
    • Continuous System-Permit-Required Confined Space

Attributes associated with hazards:

  • May contain a hazardous or potentially hazardous atmosphere (fuel storage tank).
  • May contain a material which can engulf an entrant (grain silo)
  • May contain walls that converge inward or floors that slope downward and taper into a smaller area which can trap or asphyxiate a person (coal silo)
  • May contain physical hazards such as unguarded machines or exposed live wires (process vessels)

Confined spaces with these potential hazards are permit-required confined spaces that must be identified by the employer. Typically a sign or label will be used to identify permit-required confined spaces. Workers who are exposed to a permit-required confined space must be informed of their existence and location, and be informed about their hazards.

The existence of one or more permit-required confined spaces requires that the employer have a program for controlling, and where appropriate, for protecting employees from permit-required confined space hazards and for regulating employee entry into the permit-required confined spaces.

What should you do if you need to enter a permit-required confined space?

  • Do not enter any confined space without being full informed about the space and the hazards of that confined space.  Do not rely on there being a sign or label identifying a space as a permit-required confined space. Don't make assumptions.
  • Do not enter permit-required confined spaces without having a permit to enter that space.
  • Be sure you have the appropriate training before entering a permit-required confined space.
  • Review, understand and follow the established procedures before entering a permit-required confined space.
  • Identify and know how and when to exit the confined space.
  • Before entry, identify any physical hazards.
  • Before and during entry, test and monitor the atmosphere in the confined space for oxygen content, flammability, toxicity or explosive hazards.
  • Follow the entry procedures for the permit-required confined space you are entering.  Use the required fall protection, ventilation, air-monitoring, rescue, lighting and communication equipment.
  • When in a confined space maintain contact at all times with a trained attendant either visually, using a wired phone, or using a two-way radio. If there is a problem, the communications system allows the attendant or entry supervisor to order you to get out of the confined space evacuate or to call on trained rescue personnel.

Ensure your workers are safe and are following proper protocol. Download our free Confined Space Best Practices guide below.