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LEGISLATIVE INTERPRETATIONS

OCCUPATIONAL HEALTH AND SAFETY ACT

Confined space – Definition – Hazardous

Topic: Confined space – Definition – Hazardous Issued By: Director, Compliance and Regulatory Review
Statute: General Regulation 91-191 Date Issued: November 13, 2019
Section: 262 Date Revised:

Definition

262 In this Part “confined space” means an enclosed or partially enclosed space not designed or intended for continuous human occupancy with restricted access or egress and which is or may become hazardous to a person entering it because of its design, construction, location, atmosphere or the materials or substances in it or other conditions.

Question

How can I determine if a space “is or may become hazardous”?

Answer

For a space to be considered a confined space, it must meet the following four components within the definition:

  1. Enclosed or partially enclosed space.
  2. Not designed or intended for continuous human occupancy.
  3. With restricted access or egress.
  4. Is or may become hazardous to a person entering it because of its:

    • Design
    • Construction
    • Location
    • Atmosphere or the materials or substances in it or other conditions.

While all components of the definition must be addressed, to answer this question the focus is on determining whether or not a work space is or may become hazardous to a person entering it.

Many different spaces could potentially be considered confined spaces and each one has unique characteristics and a different set of potential hazards. Therefore, the application of this part of the confined space definition is the most complex and a careful assessment and identification of hazards in and around the particular space must be conducted to determine if a specific space is or could become hazardous. Examples from each of the four elements listed in #4 above can help determine what would make a space hazardous to a person entering it.

Design: Tight work spaces; size of the work area; long narrow openings to access work area (tunnel-like); equipment or piping in the space; etc.

Construction: Installed baffles or equipment restricting access/egress; material used for space (iron vs. stainless steel, wood vs. plastic) that may interact or interfere with the work that is being done; etc.

Location: High off the ground or located underground; work area located far away from the entry/exit; space located in an area where it can accumulate dangerous gases (for instance below ground near a source for a heavier-than-air gas); space close to (potential) emission source; etc.

Atmosphere or the materials or substances in it or other conditions: Gases or liquids that may cause acute toxicity (ammonia, hydrogen sulphide, methane, carbon monoxide, nitrogen, carbon dioxide, etc.); flammable gases, liquids, or solids, or combustible dusts (fire, explosion); liquids or solids that may entrap or engulf someone (water, grain, sand, mud, etc.), oxygen deficiency (for example through hot work, a chemical reaction such as rusting or biological activity in the space), extreme heat or cold (thermal stress). While these are only a few examples known to be dangerous, many more hazardous conditions are potentially present in work spaces with the potential to cause serious injury, irreversible health conditions, or death.

It is important to point out that the confined space definition includes spaces that may become hazardous. In other words, a given hazard does not have to be present to meet the definition; the potential of the hazard being present is enough. For instance, if there is no hazardous atmosphere present in the space at the beginning of the work, but a hazardous atmosphere might develop (as a result of the work performed or due to other conditions), the space may become hazardous, and therefore meets this part of the confined space definition.

It is also important to note that the work to be performed in a space might make an otherwise non-hazardous space hazardous, and therefore it has to be considered in the aforementioned assessment of hazards in and around the space. For instance, performance of hot work in the space may introduce an atmospheric hazard (such as carbon monoxide or oxygen deficiency).

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