How to Recognize the ‘Confined Spaces’ in Your Workplace


Of all of the hazards in the workplace, confined spaces are among the most dangerous—and not only for workers who enter such spaces but also rescuers coming to the aid of workers in trouble. To comply with OHS requirements for confined spaces, you first need to recognize the “confined spaces” in your own workplace. Some confined spaces are obvious, such as manholes, boilers, tunnels, wells, storage tanks, vats, silos and trenches. But not all confined spaces are so easily recognized. For example, did you know that the loft in a wind energy tower is a confined space? Failing to identify an area as a confined space and implementing the necessary safety measures to protect workers in that area could have catastrophic results.

We’ll show you how to determine which areas in your own workplace qualify as a confined space under the law. There’s also a chart that provides the definition of “confined space” under the OHS law in each jurisdiction.

ONLINE RESOURCE: Download Model Checklist – PDFWORD


Why are confined spaces so dangerous? Because many of the hazards that may be present in a confined space aren’t easily seen, smelled, heard or felt. But they can still be deadly. For example, confined spaces typically have poor ventilation. So a toxic, odorless gas could build up in the space and overcome workers before they even realize they’re in danger. Even if workers in confined spaces become aware of a hazard, their limited means of exit could prevent escape. Some confined spaces, such as trenches, also pose the risk of collapse.

That’s why every jurisdiction’s OHS laws require employers to take special precautions to protect workers from the hazards posed by what they define as “confined spaces”  (called “enclosed areas” in Québec). Of course, you can’t implement the required safety measures for work in a confined space until you understand the definition of this term in your jurisdiction’s OHS law and use it to identify all of the confined spaces in your workplace. (See the chart at the end of article for your jurisdiction’s definition of “confined space.”)

Although there are some slight differences, the jurisdictions all generally describe confined spaces as having the same four characteristics. An area is considered a confined space if it:

  1. Is enclosed or partially enclosed;
  2. Isn’t designed or intended for continuous human occupancy but large enough for a worker to enter to perform work;
  3. Has restricted or limited means of entrance and exit; and
  4. Is or may become hazardous to anyone entering it because of its design, construction, location, atmosphere, materials or substances in it, work done in it or other conditions.

Insider Says: Most OHS laws require an area to exhibit all four of these characteristics to be considered a confined space. But there are some variations. For example, Saskatchewan has separate definitions for “confined space” and “hazardous confined space.” A “confined space” exhibits the first three characteristics; a “hazardous confined space” is a confined space that also exhibits the fourth characteristic. In Alberta, you need to read two definitions: “confined space” and “restricted space,” which is used in the definition of “confined space.”


Identifying confined spaces in your workplace might not be as easy as you think. Let’s look at each of the common characteristics of confined spaces and see how they apply in real-life workplace situations.

1. Enclosed or Partially Enclosed

The first thing to consider is whether the space is sufficiently enclosed. A space can be confined if it’s:

  • Completely enclosed—that is, contained on all sides, underneath and overhead; or
  • Partially enclosed—that is, unenclosed on one side (or the top and bottom) and enclosed everywhere else.

One objective of confined space requirements is to protect workers in a space that’s penned in, making it easy for gases or exhaust from equipment to build up inside—one of the prime hazards of confined spaces. So if the area a worker enters poses that hazard, it’s almost surely a confined space under the law.

And don’t take the word “confined” too literally. “Confined” spaces aren’t necessarily small and tight. For example, a ship’s hold could be considered a confined space even if there’s plenty of room inside it for several workers to work at one time.

2. Not Designed or Intended for Human Occupancy

If you’ve determined that the area in question isn’t completely or partially enclosed, it’s not a confined space. But if it is enclosed, then you must determine whether it was designed or intended for human occupancy. Confined spaces aren’t meant to be used by workers for regular or ongoing work. Thus, they don’t have the ventilation systems, lighting and other safeguards that usual work spaces have. In general, confined spaces are those that workers must enter only to carry out distinct operations, such as to:

  • Conduct an inspection;
  • Make a repair;
  • Take samples;
  • Performance maintenance work; or
  • Construct or install something, such as parts.

Spaces that are continuously occupied in the course of business operations are likely to be considered designed or intended for human occupancy. For example, a walk-in freezer is completely enclosed. However, it’s also designed for human occupancy because chefs and other workers are expected to go into the freezer regularly to, say, select meat for that night’s dinner menu, unpack perishables or take inventory. As a result, a walk-in freezer is likely to have a ventilation system, easy point of entry/exit, adequate lighting and other safeguards that confined spaces don’t have. Thus, a freezer wouldn’t be considered a confined space under the law. Other examples of enclosed spaces that generally aren’t confined spaces under the law because they’re designed for human occupancy are boiler rooms and mechanical rooms.

3. Restricted or Limited Means of Entrance and Exit

If the area in question is enclosed and isn’t designed for human occupancy, you should next consider whether it has limited means of entrance and exit. One of the dangers of working in a confined space is that it may be hard for workers inside to escape—and rescuers outside to get in—if a crisis takes place. For example, the only way in or out of a confined space may be by ladder or a steep staircase or through a very narrow opening. Or physical obstructions, such as bulkheads, piping or machinery, may block entry and exit.

4. Is or May Become Hazardous

Finally, for an area to be considered a confined space, it must also be or possibly become hazardous to workers or anyone else who enters it. A confined space may be hazardous because of its:

  • Design or construction—for example, trenches may be hazardous because their walls could collapse on workers;
  • Location—for example, a confined space that’s near a water source may be at risk of flooding;
  • Atmosphere—confined spaces generally have poor ventilation and so it’s easy for a dangerous atmosphere to develop. For example, toxic gases could build up or the oxygen level could plummet. Even confined spaces with open tops (such as pits) can develop a dangerous atmosphere if a gas that’s heavier than air is released and settles in the bottom of the space;
  • Materials or substances in it—for example, the presence of manure or sewage in a confined space poses a hazard to workers;
  • Work done in it—for example, use of gasoline-powered equipment in a confined space could lead to carbon monoxide poisoning; or
  • Other conditions, such as the weather.

Insider Says: Just because an area doesn’t qualify as a confined space under the law doesn’t mean that your company doesn’t have to protect workers who work in it. Such areas may still endanger workers in many of the same ways as confined spaces. So if you conclude that an area in your workplace isn’t a confined space, you should still conduct a risk assessment of that area and take all appropriate safety measures to address any hazards you identify.

ONLINE RESOURCE: Download Model Checklist – PDFWORD


Confined spaces can be found in nearly every workplace. It’s easy to identify the most common types. But it’s the less common confined spaces that can trip up a safety coordinator. By being aware of the common characteristics of confined spaces, you’re more likely to spot confined spaces and ensure that your company takes the appropriate steps to protect workers who have to enter them.

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