Most concrete crews never think of themselves as confined space workers. Then a job comes along with a water vault to form, a lift-station chamber to patch, an elevator pit to pour, or a sump to core into, and the question arrives at seven in the morning with the truck already on the way: does anyone need a permit to get down there?
In Alberta the answer does not depend on how the space feels. It depends on two definitions in the Occupational Health and Safety Code, and on which one the space meets. Get that reading right and the rest of Part 5 falls into place. Get it wrong and you have workers in a space with no permit, no atmospheric reading and nobody at the hatch.
After 38 years pouring concrete in Calgary, we have learned that this is one of the few hazards where the paperwork genuinely has to come before the pour date, not after it.
The short answer
If a space is enclosed or partially enclosed, is not designed for continuous human occupancy, and is hard to get into or out of because of the way it is built, it is a restricted space. If that same space may also become hazardous — because of the atmosphere in it, because of conditions inside it that can change, or because of the work being done in it — it is a confined space, and the full weight of Part 5 applies, including an entry permit.
Part 5 covers both. The confined space classification is the one that adds the permit.
Restricted space or confined space?
Alberta’s own guidance states the definitions plainly. A restricted space is “any space that: is enclosed or partially enclosed; isn’t designed or intended for continuous human occupancy; and has a restricted, limited or impeded means of entry or exit because of its construction.” A confined space is “any restricted space that may become hazardous” because of an injurious atmosphere, a changing set of circumstances inside, or the inherent characteristics of the activity being carried out in it.
That last clause is the one crews miss. The space can be perfectly benign when you look into it and still be a confined space, because of what you are about to do in it.
| The space | Likely reading | Why |
|---|---|---|
| Formed water or utility vault, lid off, nothing running | Restricted space | Enclosed, not for occupancy, awkward entry, no atmospheric hazard yet |
| Same vault, but a fuel-fired heater is running to hold cure temperature | Confined space | The heater creates the hazardous atmosphere; the activity is what changes the classification |
| Lift-station or sanitary chamber tie-in | Confined space | Sewer gas, oxygen deficiency, and conditions that change without warning |
| Elevator pit with waterproofing or a solvent-based product going in | Confined space | Vapours collect in the lowest point of the structure |
| Deep sump being cored from inside | Confined space | Dust and exhaust from the saw or ring drill, plus limited exit |
| Crawl space under a formed slab, open on one side | Restricted space, reassess daily | Partially enclosed and awkward, but reclassify the moment heating, coating or cutting starts |
Where these spaces show up on concrete work
The Canadian Centre for Occupational Health and Safety lists utility vaults, manholes, pump stations, tanks, access shafts, pits, trenches and ditches among its examples. On a Calgary concrete project that translates into a short, predictable list:
- Cast-in-place water, sanitary and storm chambers, including the day you strip the forms
- Elevator pits, sump pits and service pits in commercial slabs
- Formed tanks, cisterns and reservoirs before the lid is cast
- Existing structures you are coring or saw-cutting into from the inside
- Any enclosed pour being heated with a fuel-fired unit through a Calgary cold snap
That last item deserves its own sentence. A hoarded basement or a tarped vault with a fuel-fired heater running is a space whose atmosphere you have changed yourself. The Code’s definition catches it through the clause about a condition or changing set of circumstances inside the space. Nothing about the structure changed; the hazard arrived with the heater.
What Part 5 actually asks for
Part 5 runs from section 44 to section 58. Read as a sequence it is a project plan, not a list of rules.
| Section | Requirement | Who owns it |
|---|---|---|
| 44 | Written code of practice | Employer, before work starts |
| 45 | Hazard assessment by a competent person | Employer, revised when conditions change |
| 46 | Training for entrants, tenders and rescuers | Employer |
| 47 | Entry permit system (confined spaces only) | Supervisor on site |
| 48 | Equipment available, inspected, and a working communication system | Employer and supervisor |
| 49 | Isolation of hazardous substances and energy | Employer |
| 50 | Only authorized persons enter | Supervisor |
| 51 | Protection from traffic hazards | Supervisor |
| 52 | Pre-entry and ongoing atmospheric testing by a competent worker | Supervisor and tester |
| 53 | Ventilation and purging | Employer |
| 54 | Inerting, and the breathing apparatus it forces | Employer |
| 55 | Emergency response plan with on-site rescue capability | Employer |
| 56 | Tending worker at or near the entrance | Supervisor |
| 57 | Safe means of entry and exit for workers and rescuers | Employer |
| 58 | Retaining records | Employer |
The code of practice comes before the first entry
Section 44 is the one that cannot be improvised on a Tuesday. Alberta’s guideline for developing a confined space entry code of practice sets out what the document has to contain:
- A description of the confined spaces at the work site
- The reasons for work that requires entry
- Identification of the hazards that may be present
- Worker training requirements
- The entry permit system
- Procedures for each type of entry and for the work done inside
- Testing the atmosphere
- Ventilation, purging and inerting
- Isolation of hazardous substances and energy
- Emergency response
- The roles and responsibilities of the tending worker
- Recordkeeping requirements
The Explanation Guide adds two things worth underlining: the code has to identify the locations of confined and restricted spaces at the site, and it has to be kept current through periodic review. A code written for a different project, with a different set of chambers, is not a code for this one.
The entry permit, and when it quietly expires
A permit is required for confined spaces, not for restricted spaces. It names the workers and the reason for entry, identifies the space, states the period for which it is valid, and lists the precautions specific to the work being done.
The part that catches sites out is expiry. A permit stops being good when the space goes back into service, when supervision breaks, or when there is a significant interruption to the work. In practice that means the permit written at eight in the morning does not carry the crew through a lunch break, a shift change, or the hour the chamber spent back under pressure. A new reading and a new permit is the cheaper of the two outcomes.
Testing the atmosphere, and the three readings that put someone at the hatch
Testing is done before entry by a competent worker, with equipment calibrated to the manufacturer’s specifications, and continues during the work on a frequency driven by the hazard assessment. Where the atmosphere or the concentration of an airborne substance can change unpredictably, continuous monitoring is required. Every result is recorded.
Section 56 then uses those readings to decide whether a tending worker has to be stationed at or near the entrance. A tending worker is required when any of the following is true:
- Oxygen content is less than 19.5 percent by volume
- Oxygen content is greater than 23.0 percent by volume
- A substance listed in the Code’s exposure limit tables is present above 50 percent of its occupational exposure limit
- Any other identified hazard cannot be eliminated or controlled
Alberta’s code of practice guideline uses the same two figures, describing air below 19.5 percent oxygen as oxygen deficient and air above 23 percent as oxygen enriched. CCOHS gives the same range and notes that the exact numbers vary slightly between Canadian jurisdictions — which is a good reason to work to the Alberta figures and not to a template borrowed from another province.
The tending worker’s job is specific: know how many people are inside, keep constant communication with them, be able to summon help, and stay there until everyone is out or another tending worker takes over. Where the trigger conditions do not apply, a competent worker designated by the employer still has to maintain communication with the workers inside.
Rescue is a plan you own
Section 55 requires an effective emergency response plan that allows rescue and immediate evacuation, with on-site rescue capability. Calling 911 and waiting is not a plan.
The reason is in the statistics. CCOHS reports that an estimated 60 percent of confined space fatalities have been among the would-be rescuers. The person who goes in after a collapsed worker, without an apparatus and without a tender, is the second casualty in the great majority of these events. That single figure is the strongest argument for the equipment and the retrieval system required by section 48 being on site, inspected, and in working order before anyone enters — not available from a yard across town.
Section 58 closes the loop: permits, test results and entry records have to be kept, and the Code sets a minimum retention period that lengthens if there has been an incident.
Where this page stops
This page is about Part 5 and the spaces it covers. It does not deal with excavation and trench protection, which has its own part of the Code and its own engineering triggers. It does not deal with respirable dust limits from cutting, grinding or coring, with hand-arm vibration, with first aid coverage and working alone, or with powered mobile equipment training — all of which are separate obligations. It also does not decide who holds the prime contractor designation on your site. Those are different questions with different answers.
What it does settle is the sequence. Classify the space, write and localize the code of practice, assess the hazards, train the people, test the air, issue the permit, post the tender, and have the rescue capability on site. In that order.
FAQ
Is a trench a confined space in Alberta? It can be. A trench is listed by CCOHS among the examples of spaces that can become confined. The deciding factor is whether it may become hazardous because of the atmosphere, changing conditions, or the work being done in it. Trench wall protection is governed separately.
Do we need an entry permit for a restricted space? No. The permit requirement in section 47 applies to confined spaces. Restricted spaces still fall under Part 5 for hazard assessment, training, communication and safe entry and exit.
Who is allowed to do the gas test? A competent worker, using equipment calibrated to the manufacturer’s specifications. The results have to be recorded.
Does a confined space code of practice from a previous project work? Not on its own. The code has to identify the confined and restricted spaces at the work site in question and be kept current through periodic review.
Can one tending worker cover two chambers? No. The tending worker has to be stationed at or near the entrance, maintain constant communication with the workers inside, and stay until everyone is out or a replacement takes over.
Does this apply to a residential basement we are heating? If the space is enclosed or partially enclosed, is not intended for occupancy, is awkward to get out of, and the heater has changed the atmosphere, then yes — reassess it rather than assuming the answer.
Working with a contractor who plans this before the pour
Confined space work is not where you want to be improvising. Across 52,000+ projects, the jobs that went smoothly were the ones where the chamber, the vault and the pit were identified at the planning stage, not on the morning the crew arrived.
If your project includes cast-in-place chambers, pits or tanks, talk to us early about concrete foundations and structural work in Calgary, or about concrete cutting and coring into an existing structure. For related planning questions, our guides to footing depth requirements in Calgary, steps and landings for walk-out basements and the signs of foundation problems cover the ground above the hatch.
This page is general information about Alberta’s occupational health and safety requirements, not legal or safety advice for a specific work site.
Sources
- Alberta OHS Code, Part 5 — Confined Spaces (section list): https://search-ohs-laws.alberta.ca/legislation/occupational-health-and-safety-code/part-5-confined-spaces/
- Occupational Health and Safety Code Part 5 Explanation Guide, Government of Alberta: https://open.alberta.ca/dataset/757fed78-8793-40bb-a920-6f000853172b/resource/c5120beb-0eed-4b27-b88c-57bf326fd5fb/download/4403880-Part-5-Confined-Spaces.pdf
- Guideline for Developing a Code of Practice for Confined Space Entry, Government of Alberta: https://open.alberta.ca/dataset/eb357dda-9700-4ef2-a084-221edded8c9a/resource/f5ea3828-5bb4-4238-b430-4bbd081a7e31/download/whs-pub-cs001.pdf
- Confined Space – Introduction, Canadian Centre for Occupational Health and Safety: https://www.ccohs.ca/oshanswers/hsprograms/confinedspace/confinedspace_intro.html