Confined Space Work in Ontario: What O. Reg. 632/05 Requires

Confined spaces are among the most dangerous places a worker can be asked to enter. Tanks, vaults, silos, and vessels can hold atmospheric hazards that a worker cannot see, smell, or feel until it is too late. In Ontario, work in these spaces is governed by Ontario Regulation 632/05, made under the Occupational Health and Safety Act (OHSA). This article explains, in plain language, what the regulation requires before anyone goes in.

What counts as a confined space?

Under O. Reg. 632/05, a space is a confined space when it meets three conditions at the same time. It is:

large enough that a person can bodily enter it,
has restricted means of entry or exit, and
is not designed for continuous human occupancy.

All three have to be true. A space that a worker can enter but that has an ordinary door and is meant for people to occupy is not a confined space. It is the combination of enterable size, a difficult way in and out, and a design never intended for people to stay in that creates the risk the regulation is built to control.

What the regulation requires

O. Reg. 632/05 does not treat confined space entry as something a crew decides to do on the spot. It requires a system to be in place before anyone approaches the space.

A written confined space program: Employers must develop and maintain a written confined space program. This is the governing document that sets out how the organization identifies its confined spaces and controls the hazards inside them.

A written hazard assessment: Before entry, there must be a written assessment of the hazards specific to that space. Confined space hazards are not identical from one space to the next, so the assessment is done for the actual space being entered.

An entry permit: Entry is authorized through a written entry permit. The permit documents the conditions under which entry is allowed and records the results of testing so that everyone on the job is working from the same verified information.

Atmospheric testing: Before entry, the atmosphere inside the space must be tested. The regulation sets the acceptable limits:

Oxygen: between 19.5 and 23 percent
Flammable gas or vapour: below 25 percent of the Lower Explosive Limit (LEL)
Toxic contaminants: within their occupational exposure limits

Testing must be done with calibrated equipment, operated by a person trained to use it, and the results must be recorded on the permit. These atmospheric and testing requirements are set out in O. Reg. 632/05, sections 11 to 18.

The roles: entrant, attendant, competent person, rescue

Confined space work is a team activity with defined roles, and no one role can safely cover the job alone.

Entrant: the worker who goes into the space to do the work.
Attendant: stationed outside the space, the attendant must remain outside for the duration of the entry, maintaining contact with the entrant and watching for trouble.
Competent person / entry supervisor: the person responsible for verifying that conditions are safe and that the entry is authorized.
Rescue team: the people prepared to respond if the entrant needs to be brought out.

Keeping the attendant outside is not a technicality. If the attendant enters to help, the workplace loses the one person whose job is to watch, call for help, and coordinate a rescue.

Rescue must be planned before entry

One of the most important requirements in O. Reg. 632/05 is that rescue is not improvised after something goes wrong. On-site rescue procedures, the right rescue equipment, and a written rescue plan must all be in place before any worker enters the confined space.

This ordering matters because a large share of confined space fatalities are would-be rescuers who rushed in without training, equipment, or a plan and became the next casualty. Having the rescue capability ready before entry, rather than assembling it in an emergency, is what keeps a bad situation from becoming a worse one.

Frequently asked questions

Does every enterable tank or pit count as a confined space? Only if all three conditions are met: it is large enough to enter, has restricted means of entry or exit, and is not designed for continuous human occupancy. If any one of those is not true, it does not meet the regulation's definition.

Who can perform the atmospheric testing? Testing must be carried out with calibrated equipment by a person trained to operate it, and the results must be recorded on the entry permit.

Can the attendant help with the work inside? No. The attendant must remain outside the space throughout the entry. Their role is to monitor the entrant and coordinate a response if something goes wrong.

Is there a national standard as well as the Ontario regulation? Yes. CSA Z1006 is the national standard for managing work in confined spaces, and it is commonly used alongside O. Reg. 632/05.