What Is a Confined Space? Definition & Examples

Last updated: March 2026

A confined space is any area that was not designed for continuous human occupancy, has restricted entry and exit, and could expose workers to serious hazards. Understanding the exact definition matters because it determines what safety requirements apply to your crew before anyone sets foot inside.

What Is a Confined Space?

A confined space is any enclosed or partially enclosed area that was not designed for people to work in continuously, has limited ways to get in or out, and could expose your crew to serious hazards. Think tanks, manholes, vaults, silos, and crawl spaces. They show up on almost every construction, oil and gas, manufacturing, and mining site in Canada.

If you run a 10- to 100-person contracting crew, you have probably walked past a confined space this week without flagging it. That matters because the regulations around confined spaces carry real teeth. Missing one can mean stop-work orders, fines, or worse. This guide breaks down the confined space definition under Canadian law, explains how to identify these spaces on your jobsite, and gives you practical examples by industry so nothing slips through the cracks.

The Legal Definition of a Confined Space in Canada

There is no single national definition that applies everywhere. The rules depend on whether your work falls under federal or provincial jurisdiction, and each province uses slightly different language. Here is what the key regulators say.

Federal. Canada Occupational Health and Safety Regulations (COHSR), Part XI

Under the amended Part XI of the COHSR, a confined space is an enclosed or partially enclosed space that:

1. Is not intended or designed for continuous human occupancy
2. Has restricted means of access or egress
3. May contain a hazard (atmospheric, engulfment, entrapment, or other)

The federal regulations also distinguish between a regular confined space and a hazardous confined space, which is a confined space where the hazards have been confirmed through testing or assessment. This matters because the entry requirements for a hazardous confined space are more stringent, including mandatory entry permits and rescue plans.

Federal rules apply to workplaces under the Canada Labour Code: interprovincial transport, telecommunications, federal Crown corporations, and First Nations. If your jobsite is provincially regulated (most construction and oil and gas operations), your provincial OHS code is what applies.

Alberta. OHS Code, Section 1 and Part 5

Alberta takes a layered approach. The OHS Code defines two categories:

Restricted space: An enclosed or partially enclosed space, not designed or intended for continuous human occupancy, that has a restricted, limited, or impeded means of entry or exit because of its construction.

Confined space: A restricted space that may become hazardous to a worker entering it because of:

• An atmosphere that is or may be injurious (oxygen deficiency or enrichment, flammability, explosivity, or toxicity)
• A condition or changing set of circumstances within the space that presents a potential for injury or illness

In Alberta, every confined space is first a restricted space. It becomes a confined space once a hazard potential is identified. That distinction drives the level of controls. Restricted spaces still require a hazard assessment, but confined spaces require a full code of practice, entry permits, and dedicated safety procedures.

Ontario. O. Reg. 632/05 (Confined Spaces)

Ontario defines a confined space as a fully or partially enclosed space that:

1. Is not both designed and constructed for continuous human occupancy
2. Has a risk of atmospheric hazards because of its construction, location, contents, or work done inside it

Ontario's definition is narrower than Alberta's or BC's because it focuses specifically on atmospheric hazards. Physical hazards like engulfment or entrapment alone do not trigger the confined space regulation in Ontario, though they are still covered under the general duty clause of the OHSA.

British Columbia. OHS Regulation, Part 9 (Section 9.1)

WorkSafeBC defines a confined space as an area, other than an underground working, that:

1. Is enclosed or partially enclosed
2. Is not designed or intended for continuous human occupancy
3. Has limited or restricted means for entry or exit that may complicate the provision of first aid, evacuation, rescue, or other emergency response
4. Is large enough and so configured that a worker could enter to perform assigned work

BC's definition is notable because it does not require a hazard to be present for a space to qualify as confined. If it meets the four physical criteria above, it is a confined space under Part 9 regardless of atmospheric conditions. Hazard classification (low, moderate, or high hazard atmosphere) comes later and determines the level of controls required.

The 3 Characteristics That Define a Confined Space

Despite the differences in wording across jurisdictions, every Canadian confined space definition comes back to three core characteristics. If a space checks all three boxes, you are almost certainly dealing with a confined space:

1. Enclosed or Partially Enclosed

The space has walls, a floor, and a ceiling (or some combination) that restrict airflow and create a contained environment. It does not need to be fully sealed. A pit with an open top can still qualify if the walls are deep enough to trap gases or restrict air movement.

2. Not Designed for Continuous Human Occupancy

The space was built for storing material, housing equipment, moving fluids, or some other purpose that is not "people working here all day." A mechanical room with ventilation, lighting, and exits built to building code standards is designed for human occupancy. A storage tank is not.

3. Restricted Entry or Exit

Getting in and out is not straightforward. Maybe the opening is a manhole cover. Maybe you need a ladder. Maybe the only way out is the same way in. If entry or exit could slow down rescue or evacuation, this criterion is met.

When you are standing on site wondering what is considered a confined space, run through these three questions. If the answer to all three is yes, treat it as a confined space until a proper assessment says otherwise.

Confined Space Examples by Industry

Confined spaces are not always obvious. Here are common examples grouped by the industries where Canadian contractors encounter them most often.

Construction

• Manholes and utility vaults, sewer, storm, and electrical access points
• Deep excavations and trenches, especially those deeper than 1.2 metres with limited exits
• Concrete formwork and caissons, enclosed pours and foundation structures
• Crawl spaces under buildings, limited clearance, restricted airflow
• Pipe runs and large-diameter piping, anything 600 mm or larger that a worker can enter
• Elevator shafts during construction, before permanent ventilation and egress are installed

Oil and Gas

• Storage tanks and pressure vessels, the classic confined space
• Separators and treaters, residual H2S gas, hydrocarbon vapours, and oxygen displacement
• Pipeline segments, during maintenance, pigging, or tie-in work
• Flare knock-out drums, accumulated liquids and toxic atmospheres
• Mud tanks and reserve pits, drilling waste and gas accumulation

Manufacturing

• Mixers, blenders, and reactors, chemical residue, moving parts, oxygen displacement
• Hoppers and bins, engulfment hazard from stored materials
• Boilers and furnaces, residual heat, combustion gases
• Ductwork and ventilation plenums, large enough for a worker to enter for cleaning
• Tank trucks and rail cars, portable confined spaces that show up across sites

Mining

• Ore passes and chutes, engulfment and fall hazards
• Sumps and settling tanks, water, slurry, and chemical accumulation
• Equipment compartments, large mobile equipment enclosures during maintenance
• Ventilation raises and shafts, oxygen depletion and gas accumulation underground

When doing your job hazard assessment, walk the site with this list in mind. If a space shows up that looks like it fits, flag it for a formal confined space assessment.

What Is NOT a Confined Space

Knowing what is a confined space also means knowing what is not. These are the misconceptions that trip up contractors most often:

Small rooms are not automatically confined spaces

A mechanical room, storage closet, or basement workshop with normal doors, lighting, and ventilation is designed for human occupancy. It might be cramped, but "small" does not equal "confined" under the regulations. The key question is whether the space was designed and constructed for people to work in continuously.

Open-top spaces can still be confined spaces

A common misconception is that a space needs to be fully enclosed to qualify. A deep pit, an open-top tank, or a below-grade vault can absolutely be a confined space if gases can accumulate, access is restricted, and it was not designed for continuous occupancy.

Regular offices and workshops are not confined spaces

If the space meets building code requirements for ventilation, egress, and lighting, and it was designed for people to occupy continuously, it is not a confined space. This is true even if the space feels enclosed or has limited windows.

Attics and crawl spaces need evaluation

In some provinces (like BC), certain crawl spaces and attics in non-industrial buildings may be excluded from confined space rules if specific criteria are met, including clean air, natural ventilation, and no potential for hazardous atmospheres. But this exclusion requires a formal evaluation. Do not assume.

The "big enough to enter" rule

If a worker cannot physically enter the space (the opening is too small for a person's body to pass through), it typically does not qualify as a confined space under the regulations. However, any work involving reaching into such spaces still falls under general OHS duty-of-care requirements.

How to Identify Confined Spaces on Your Jobsite

If you do not have a dedicated safety manager, use this practical checklist to evaluate spaces on your site. Run through it for every space your crew might need to enter.

Confined Space Identification Checklist

1. Walk the site. Look at every structure, pit, tank, vault, crawl space, and enclosure your crew might enter.
2. Ask the three questions: Is it enclosed or partially enclosed? Not designed for continuous human occupancy? Restricted entry or exit?
3. Check for hazards. Could atmospheric hazards develop (toxic gases, oxygen depletion, flammable vapours)? Are there engulfment risks (grain, sand, water)? Physical hazards (moving parts, energized equipment)?
4. Review previous work. Has anyone entered this space before? What conditions did they find?
5. Document everything. Your provincial OHS code requires you to identify and list all confined spaces at your worksite. In Alberta, this goes into your written code of practice.
6. Post signage. Every identified confined space needs clear signage warning workers not to enter without authorization and a valid entry permit.
7. Get a competent person involved. If you are unsure whether a space qualifies, bring in someone with the training and experience to make that call. Your field-level hazard assessment process should flag potential confined spaces as part of pre-work planning.

Keep your confined space inventory current. New spaces can appear as construction progresses, equipment gets installed, or site conditions change. Review it at the start of every new project phase.

Confined Space vs Restricted Space

If you work in Alberta, you have probably heard both terms. Here is the quick distinction:

• Restricted space: Meets the physical criteria (enclosed, not designed for continuous occupancy, restricted access) but has no identified hazards beyond those physical characteristics.
• Confined space: A restricted space where hazards have been identified or may develop, including atmospheric hazards, engulfment, entrapment, or other conditions that could injure a worker.

In practical terms, a restricted space still requires a hazard assessment, worker training, and precautions. But a confined space triggers the full set of requirements: written code of practice, entry permits, atmospheric testing, attendants, rescue plans, and emergency equipment.

Ontario uses the terms differently. Under O. Reg. 632/05, "restricted space" appears only in the healthcare facilities regulation (O. Reg. 67/93) and refers to spaces with restricted egress. It is a separate concept from the confined space definition.

BC does not use the term "restricted space" in its confined space regulation at all. If it meets the four criteria in Part 9, it is a confined space, and the hazard classification (low, moderate, or high) determines what controls apply.

Provincial Definition Differences at a Glance

If your crews work across provinces, do not assume that a space classified one way in Alberta will be classified the same way in Ontario. The definitions are close but not identical. Always check the local regulations before starting work.

Next Steps

Understanding the confined space definition is the first step. From here, the practical work begins:

• Identify every confined space on your current jobsite using the checklist above
• Assess the hazards in each space with a competent person (see our guide to confined space safety for contractors)
• Get your workers trained on confined space entry procedures, atmospheric monitoring, and emergency response
• Build your written program, your province requires it before anyone enters a confined space
• Set up your field-level hazard assessment process to flag confined spaces during pre-work planning

If your safety program does not have a confined space section yet, Safety Evolution software can analyse your existing records to identify which spaces qualify as confined and what documentation you need for each one.