A confined space is an enclosed or partly enclosed area that is not designed for people to work in continuously, has limited ways in and out, and could become hazardous to anyone inside. The exact legal definition depends on your province, but the idea is the same everywhere: if a worker could be trapped, overcome or unable to get out quickly, the space needs to be identified and managed before anyone enters.
The common elements of a definition
Each province writes its own definition into its occupational health and safety rules, so check the wording that applies to your sites. Most definitions share several elements:
- Enclosed or partly enclosed. The space is surrounded by walls, a shell or the ground, even if it has an open top. A pit or trench can qualify.
- Not designed for continuous occupancy. People go in to inspect, clean, repair or build, but nobody works there as a normal workstation.
- Restricted access or exit. Entry is through a manway, hatch, ladder or small opening, or the route out is long or awkward.
- Potential to be hazardous. The space may have, or could develop, a dangerous atmosphere, a risk of engulfment, or other conditions that could harm someone inside.
Some provinces separate spaces where the only real issue is awkward access from spaces that also have a hazardous atmosphere or similar hazard. Alberta, for example, uses the term restricted space for the first group. British Columbia and Ontario have their own definitions and requirements, and some federally regulated workplaces follow separate rules. The CSA Z1006 standard on managing work in confined spaces is widely used as a reference across Canada. Check the current edition and your provincial legislation.
Common examples
Confined spaces show up in almost every type of facility, often in places that people walk past every day:
- Storage tanks, process vessels, hoppers and silos
- Sewers, manholes, lift stations, wet wells and utility vaults
- Boilers, furnaces, large ducts and air handling plenums
- Pits under equipment, sumps and elevator pits in some circumstances
- Crawl spaces, attics and the space above some ceilings, depending on conditions
- Rail cars, tanker trailers and shipping containers being cleaned or repaired
- Excavations and trenches, which may also fall under separate excavation rules
Why confined spaces are so dangerous
The hazards inside a confined space are often invisible and can change in seconds. The main ones are:
Hazardous atmospheres
Oxygen can be displaced by other gases or consumed by rusting steel, bacteria or combustion, leaving too little to breathe. Flammable gases and vapours can build up from residues, leaks or the work itself. Toxic gases such as hydrogen sulphide and carbon monoxide can accumulate to lethal levels. Many of these gases have no colour or smell, or deaden the sense of smell at dangerous concentrations.
Engulfment
Grain, sand, sludge, water or other loose material can flow in and bury or drown a worker. Material that looks solid can collapse from underneath.
Energy and moving parts
Agitators, conveyors, augers, fans and connected piping can start up or release product if they are not isolated and locked out.
Configuration and environment
Sloped floors, narrowing walls and internal structures can trap a worker. Heat, cold, noise, poor lighting and slippery surfaces add to the risk and make rescue harder.
Would-be rescuers are at risk too. A large share of confined space deaths involve co-workers who went in to help someone who had collapsed. Never enter to rescue unless you are trained, equipped and part of the planned rescue. Call for the rescue team and stay outside.
How to decide whether a space is a confined space
The decision should be made by a competent person and written down. A practical approach is to:
- List every space on the site that people may need to enter, including ones entered rarely.
- For each, check it against your province's definition: enclosure, design for occupancy, access and exit, and potential hazards.
- Consider the work that will be done inside, since welding, painting, cleaning or using fuel-powered equipment can create a hazard where there was none.
- Record the result and the reasoning, and label confined spaces at each entry point.
- Review the list when equipment, processes or tasks change.
Once a space is identified, it needs a written hazard assessment, a code of practice or program, and controls such as entry permits, atmospheric testing and a rescue plan before anyone goes in.
What employers are expected to have
Requirements vary by province, but employers with confined spaces are generally expected to:
- Identify and assess each confined space
- Have a written program or code of practice
- Use an entry permit system where the hazards call for one
- Isolate energy and piping, test the atmosphere and ventilate as needed
- Train entrants, attendants, supervisors and rescuers for their roles
- Have a rescue plan and the people and equipment to carry it out
- Prevent unauthorized entry
- Keep records of assessments, permits, testing and training
The people involved each have defined duties, described in Confined space roles: entrant, attendant, supervisor.
How ehZee can help
We survey sites to build a confined space inventory, assess each space and write the program, permits and rescue plan around your province's rules. Our confined space programs service explains how the work runs from first site visit to rollout.
Common questions
Is a space with an open top a confined space?
It can be. Open-topped tanks, pits and vats can trap gases heavier than air and may be difficult to climb out of. Assess the space against your province's definition rather than assuming an open top makes it safe.
If the air tests fine, can we skip the program?
No. Atmospheres can change during the work, and other hazards such as engulfment or moving parts do not show up on a gas detector. The program and permit address all of the hazards, not only the air.
Who decides if a space is a confined space?
The employer is responsible, and the assessment should be done by a competent person who understands the space, the work and the legislation. The reasoning should be recorded.