Confined Space Awareness Course: Lessons 2026

Lesson 1: What a confined space is

A confined space is a fully or partly enclosed space that is not designed for people to work in it all the time, has limited or restricted ways in and out, and can be hazardous because of its design, location, air, contents or the work done in it. Despite the name, a confined space is not always small.

Tanks, vats, silos, hoppers and storage bins
Sewers, manholes, utility vaults and pump stations
Pipes, ducts, boilers, pits and access shafts
Rail or truck tank cars, shipping containers and fish holds

Every province and territory has confined space rules, and the definitions differ a little. Ontario's rules describe a space that is not both designed and built for continuous human occupancy, where atmospheric hazards may occur. Ontario's guideline says offices, mechanical rooms, shops, walk-in freezers and labs are designed for occupancy. In BC, the space must also be large enough for a worker to enter and do assigned work.

Lesson 2: Confined space hazards

Hazard	What it means
Too little oxygen	Normal air has about 21% oxygen. At 19.5% or less, people breathe fast, get clumsy and tired, then can collapse and die. Gases such as nitrogen, argon and carbon dioxide push oxygen out.
Too much oxygen	Extra oxygen makes fire and explosion far more likely. Never use oxygen to freshen the air.
Flammable air	Gases, vapours or dusts that can catch fire or explode
Toxic gases	For example hydrogen sulphide and carbon monoxide
Engulfment	Being trapped or buried by loose material such as grain or sand, or by flooding liquid
Other hazards	Moving machinery, heat or cold, noise, poor lighting, slips and falls, and germs from sludge or mould

Ontario treats oxygen below 19.5% or above 23% by volume as an atmospheric hazard.

Problems are more dangerous in a confined space. There is less room for error, escape and rescue are harder, fresh air does not move through easily, and conditions can change quickly.

Lesson 3: Before anyone enters

Employers need a confined space program, a hazard assessment and a plan for each space. Before entry, the usual steps are:

A competent person assesses the hazards.
Pipes and energy sources are isolated or locked out, and the space is ventilated if needed.
A trained person tests the air from outside, before anyone enters.
An entry permit is completed, and the attendant and rescue team are ready.
Workers enter only when the permit allows it. Testing continues where conditions may change.

Entry permits

In Ontario, a separate entry permit is issued each time work is to be done in a confined space. It lists the location, the work, the hazards and controls, how long it is valid, the attendant's name, each worker's entries and exits, the entry and rescue equipment, and the results of the air tests. It must be readily available to everyone who enters.

Air testing limits

Flammable gas is measured as a percentage of its lower explosive limit (LEL), the lowest amount in air that can burn or explode.

Flammable gas level (Ontario guideline)	What is allowed
Under 5% of the LEL	Hot work (sparks or flames) may be allowed
Under 10% of the LEL	Cold work, but no hot work
Under 25% of the LEL	Inspection only
25% of the LEL or more	No entry

In BC, continuous air monitoring is required if flammable gas could build up past 20% of the LEL. Pre-entry testing must be done no more than 20 minutes before a worker enters, and repeated if everyone has been out for more than 20 minutes.

Lesson 4: The attendant and rescue

In Ontario, an attendant stays outside and near the entrance while workers are inside. The attendant keeps in constant communication with them, can call for rescue right away, and does not enter the space. In BC, this role is called the standby person, who must check on the workers at least every 20 minutes in low and moderate hazard spaces, and watch them continuously where the hazard is high.

CCOHS reports that more than 60% of confined space deaths are would-be rescuers: people who went in to help without the right equipment and were overcome too.

Rescue must be ready before entry

In Ontario, nobody may enter unless written on-site rescue procedures are ready for immediate use and enough trained rescuers are available.
Rescuers are trained in the rescue procedures, first aid and CPR, and the rescue equipment.
Rescue from outside the space is preferred where possible.
Rescuers who enter should not breathe the same air: they need supplied air, such as SCBA.
In Ontario, calling 911 is not an on-site rescue procedure.

Lesson 5: Training, entry control and your role

Only trained and authorized workers may enter a confined space or do related work. Ontario's regulation requires adequate training for every worker who enters or does related work, such as attendants and rescuers, and written records of who gave and received it. CCOHS says entrant training should include hands-on practice.

This course is awareness only. It does not train or qualify you to enter a confined space, act as an attendant or take part in a rescue.

Keeping people out

In Ontario, if unauthorized entry is possible, each entrance must be secured, or have barricades, warning signs or both. In BC, access points must be secured or identified by a sign or other effective means. A confined space should never be closed up until someone has checked that no one is still inside.

No access for unauthorized persons: a sign like this may mark a confined space entrance.

Checklist for guards and site workers

Learn where the confined spaces are on your site.
Never enter one, even for a moment, unless you are trained, authorized and on the permit.
Keep covers, barricades and signs in place, and report any that are missing.
Report anyone trying to enter without authorization.
In an emergency, stay outside, raise the alarm and call for rescue as your site plan says.