Worker in a hard hat, hi-vis vest and harness kneeling well back from an open access hatch, checking a handheld gas monitor whose sampling hose runs into the opening, with a rescue tripod and winch set up over the hatch.

Regulations & Standards

Before Anyone Goes In: Confined-Space Air Testing and Rescue Planning

November 11, 20268 min read

By Riley M.

Short answer: Before anyone enters a confined space, test the air for oxygen, flammable gases and toxic gases with a calibrated monitor, record the results and have a written rescue plan, trained rescuers and equipment ready. Retest after any break and at set intervals or continuously, and keep an attendant outside who never enters.

The air inside a tank, pit, vault or hatch can look and smell normal and still kill. Oxygen can be too low, a toxic gas can build up, or a flammable vapour can collect, and none of it has to give a warning. That is why the order of operations in confined-space work never changes: test the air, keep testing it, and have a rescue plan ready before anyone goes in. When that order breaks down, the first worker in is at risk, and so is the next person who goes in to help.

Why this is in the news

On November 5, 2026, Newfoundland and Labrador's Occupational Health and Safety Division announced eight charges against Mowi Canada East following a January 2025 fatality at a worksite in Stephenville. Among the charges, the government alleges the company failed to:

conduct and record appropriate tests for harmful vapours, gases, fumes, mists, dusts, explosive substances and oxygen deficiency before entry, after an interruption in work and at appropriate intervals;
establish written rescue and evacuation procedures, including for confined spaces;
inform workers of confined-space hazards through posted signage or equally effective means; and
establish and follow emergency rescue procedures, including worker training and immediate evacuation.

These are allegations, not findings. None of the charges has been proven in court, and the company's first appearance is scheduled for November 19, 2026, in Provincial Court in Stephenville. We're not commenting on what happened at that site. What the charge list does give every employer is a clear picture of what regulators expect to see in place before a confined-space entry.

What the rules actually require

Every province and territory has its own confined-space rules, and the details differ. Two examples:

Newfoundland and Labrador (NLR 5/12, Part XXVII):

Tests for harmful vapours, gases, fumes, mists, dusts or explosive substances and oxygen deficiency must be made and recorded before entry, after an interruption in the work and at appropriate intervals (s. 512(11)).
If a test shows an unsafe condition, the space must be ventilated or cleaned, or both, and retested until oxygen is between 20% and 22%, flammables are below 10% of the lower explosive limit (LEL), and exposure to harmful substances stays within ACGIH TLVs (s. 512(12)).
Testing must be done by someone trained on the equipment, and the equipment must be calibrated and maintained to the manufacturer's instructions (s. 512(15) and (16)).
An attendant stationed outside, who never enters, must stay in contact and be able to summon rescue (s. 513), and emergency rescue procedures must be established and followed (s. 516).

Ontario (O. Reg. 632/05):

A person with adequate knowledge, training and experience must test as often as necessary, before and while a worker is inside, using calibrated instruments suited to the hazards, and every result must be recorded (s. 18).
Acceptable oxygen is at least 19.5% and not more than 23% by volume (s. 1).
No one may enter or stay in a confined space unless written on-site rescue procedures are ready for immediate use, with enough people trained in those procedures, first aid and CPR, and the rescue equipment (s. 11).
An attendant must be stationed outside, stay in constant contact and never enter (s. 15).

For the rest of Canada, CCOHS keeps a jurisdiction-by-jurisdiction summary of atmospheric testing rules. Always check the regulation that applies to your site.

The pre-entry checklist

Use this as a starting point for your own written program and entry permit.

Know where your confined spaces are, and mark them. Do a written assessment of each one and post signs or use an equally effective way to warn workers.
Write the permit before anyone enters. Record the hazards, the controls, the attendant's name, the equipment and the test results.
Isolate first. Blank or disconnect lines that could feed hazardous substances in, and lock out and tag mechanical and electrical equipment inside the space. Our lock-out/tag-out guide covers the basics. Trucks or mobile equipment parked at the space need their own steps, set out in our guide to energy control for vehicle and mobile-equipment repair.
Test the air at three moments: before entry, after any interruption in the work, and at set intervals (or continuously) while people are inside. Test for oxygen, flammable gases and vapours, and the toxic gases your assessment identified. A portable multi-gas monitor can read several of these at once.
Use a monitor you can trust. It should be calibrated and maintained to the manufacturer's instructions, with the right calibration gas and detection accessories on hand, and used by someone trained on it. Our article on the role of gas monitors explains how they work.

Dräger X-am 2800 portable multi-gas monitor for explosive gases, oxygen, carbon monoxide and hydrogen sulphide

Record every result. If it isn't written down, it can't be checked, and the next shift has nothing to go on.
Ventilate and retest if any reading is out of range. Portable confined-space ventilation blowers and ducting move fresh air into the space. Don't enter until a retest shows it's back within acceptable levels.

Orange Allegro 12-inch axial explosion-proof plastic blower with black statically conductive ducting attached

Station an attendant outside. They stay in contact, watch conditions and call for rescue. They do not go in.
Set up rescue before entry, not after. Have the retrieval system rigged, the people trained, and a way to summon help on hand.

3M DBI-SALA aluminum confined-space tripod with Salalift II winch and galvanized cable, set at a 7 ft anchor height

Train and practise. Entrants, attendants and rescuers should all know the plan, and rescue should be drilled before you ever need it.

Confined spaces are one of the hazards we cover in our overview of common workplace hazards.

Keyline Safety's stand

No one should enter a confined space until the air has been tested and a rescue plan is ready to go. Gas monitors and retrieval systems support that plan; they don't replace it. The test has to be repeated after every break and at regular intervals, the results have to be written down, and the person who would pull a worker out has to be standing at the entrance with the equipment already set up. If any of that is missing, the entry should wait.

What Keyline Safety does

We supply the equipment that a confined-space plan relies on, and we can help you match it to the hazards on your site.

Gas detection. Our Gas Monitoring and Detection Equipment range includes Dräger multi-gas monitors such as the Dräger X-am 2800 (Ex, O2, CO, H2S) and the Dräger X-am 5800 (Ex, O2, CO, H2S), Dräger Pac 8000 and Pac 8500 single-gas monitors, and the Dräger Bump Test Station for X-am 1000/2000/5000 detectors.
Retrieval and rescue. Our Confined Space Rescue and Descent Equipment range includes the 3M DBI-SALA Confined Space Aluminum Tripod with Winch 8301080, the 3M DBI-SALA Tripod with Winch and 3-Way SRL 8301074, the Dynamic Cable 3-Way Self-Retracting Lifeline with Retrieval (CSA Class SRL-R), 50 ft and 3M DBI-SALA davit components such as the Universal Davit Mast 8000109.
Ventilation. Blowers such as the Allegro 12" Axial Explosion-Proof (EX) Plastic Blower with Canister and 25 ft Statically Conductive Ducting, for moving fresh air into a space before and during entry.
Lockout for isolation. Padlocks, hasps, cable lockouts and group lockout boxes are in our Lockout / Tagout collection.
Help choosing. Tell us which gases your assessment flagged and how your spaces are accessed, and we'll help you narrow down the monitors and retrieval equipment that fit.

Dräger X-am 5800 multi-gas monitor beside its charging cradle and power adapter

Planning a confined-space entry or reviewing your rescue setup? Contact Keyline Safety through our safety assistant chat, and we'll help you find the right gas detection and retrieval equipment.

Frequently asked questions

When should the air in a confined space be tested?

Before entry, after any interruption in the work, and at set intervals or continuously while workers are inside, with every result recorded.

What is an acceptable oxygen level for confined space entry?

Ontario's O. Reg. 632/05 sets acceptable oxygen at 19.5% to 23% by volume. Newfoundland and Labrador's rules use 20% to 22% after ventilation. Check the regulation that applies to your site.

What does a confined space attendant do?

The attendant stays outside the space, keeps in constant contact with the entrants, watches conditions and calls for rescue. The attendant must never enter.

Does a confined space rescue plan have to be in place before entry?

Yes. Ontario requires written on-site rescue procedures ready for immediate use, with enough people trained in them, first aid and CPR, and the rescue equipment, before anyone enters.