Confined Space Entry Checklist

Confined Space Entry in Ontario: The Rules That Prevent Underground Deaths

The requirements below come from Ontario Regulation 632/05 (Confined Spaces) under the Occupational Health and Safety Act (OHSA). These are the rules a Ministry of Labour inspector enforces when workers enter manholes, tanks, silos, trenches, and any other space not designed for continuous human occupancy where atmospheric hazards may exist. O. Reg. 632/05 has governed confined spaces on construction projects since the 2011 consolidation (the former O. Reg. 213/91 confined-space sections were revoked and folded in).

Why confined spaces kill more workers than you think

Confined space incidents are among the deadliest workplace events in Ontario. Between 2010 and 2024, the province recorded dozens of fatalities in confined spaces — manholes, sewers, storage tanks, grain silos, and industrial vessels. What makes these deaths particularly tragic is that many of the victims are rescuers. A worker collapses from an oxygen-deficient atmosphere in a manhole. A co-worker sees them down, panics, and enters to help — without a gas monitor, without breathing equipment, without a rescue plan. Now there are two victims instead of one. In some incidents, a third person enters and dies too. This cascading rescue failure is so common that confined space training begins with a single rule: the attendant must never enter the space. O. Reg. 632/05 exists because confined spaces create invisible, instantly lethal hazards that humans cannot detect with their senses. You cannot see oxygen displacement. You cannot smell hydrogen sulfide above 100 ppm because it paralyzes the olfactory nerve. You cannot feel carbon monoxide until you are confused and unable to self-rescue. The regulation requires atmospheric testing, an attendant, a rescue plan, and an entry permit because the space itself is trying to kill you and you will not know it until you are unconscious.

What makes a space a "confined space" in Ontario?

O. Reg. 632/05 section 1 sets two tests. A confined space is a fully or partially enclosed space that (a) is not both designed and constructed for continuous human occupancy, and (b) in which atmospheric hazards may occur because of its construction, location, contents, or the work done in it. Ontario's definition turns on the atmosphere — it is narrower than the US "permit-required" definition, which also counts engulfment and mechanical hazards as stand-alone triggers. A manhole is obviously a confined space. So is a storage tank, a sewer, a silo, and a pipe large enough for a person to enter. The regulation also catches spaces workers might not label "confined": a crawl space under a building, a trench near a sewer or in contaminated ground, a pit beneath a machine, a large duct, or an attic where spray-foam off-gassing can foul the air. There is no size minimum — a vault 1 metre square and 1.5 metres deep is a confined space if a worker must enter it and the air could go bad. Once a space is in scope, the program does not stop at the atmosphere: the assessment and plan must also control engulfment, entrapment, and hazardous energy before entry.

Atmospheric hazards: the invisible killers

The four gases monitored in every confined space entry are oxygen, combustible gas (measured as percent of Lower Explosive Limit), hydrogen sulfide, and carbon monoxide. Oxygen must be between 19.5% and 23.0%. Normal air is 20.9% oxygen. Below 19.5%, workers experience impaired judgment, then unconsciousness, then death — often within minutes. Oxygen displacement happens silently: heavier-than-air gases like CO2 or nitrogen settle into low spaces and push oxygen out. A manhole that had 20.9% oxygen yesterday can have 16% today because a nearby process vented nitrogen overnight. Below 16% is Immediately Dangerous to Life or Health (IDLH). Combustible gas must be below 10% of the Lower Explosive Limit for cold work (below 25% for inspection work; hot work is stricter still). The LEL is the minimum concentration of gas in air that can ignite. At 10% LEL, you are at one-tenth of the way to an explosion — the regulation requires evacuation at this point because conditions can change rapidly and an ignition source (a spark from a tool, static electricity, a cell phone) could cause a fireball in an enclosed space with no escape route. Hydrogen sulfide (H2S) is the sewer gas that smells like rotten eggs — but only below 100 ppm. Above that concentration, it instantly paralyzes the olfactory nerve and the worker cannot smell it at all. Ontario's limit (O. Reg. 833) is 10 ppm TWA and 15 ppm STEL, and IDLH is 100 ppm. H2S is heavier than air and accumulates in low points — the bottom of a manhole, the lowest section of a sewer. Carbon monoxide is odorless and colorless at all concentrations. The TWA limit is 25 ppm (O. Reg. 833); there is no Ontario short-term ceiling, but 4-gas monitors typically high-alarm near 100 ppm, and IDLH is 1200 ppm. Sources include gasoline engines, propane heaters, and incomplete combustion. Running a gas-powered pump near a confined space opening can fill the space with lethal CO concentrations in minutes.

Do you need an entry permit every time? Yes — the permit system

O. Reg. 632/05 section 10 requires a written entry permit for every confined space entry. This is not a one-time document — each entry event gets its own permit. The permit must list: the confined space being entered, the date and authorized duration, all hazards identified in the assessment, the control measures in place, the atmospheric test results (with times), the names of the entry supervisor, attendant, and all authorized entrants, the required equipment, the communication method, and the rescue plan. The entry supervisor signs the permit to authorize entry. If any condition changes — atmospheric readings shift, unexpected noise or vibration, water ingress, ventilation failure — the permit is void and workers must exit immediately. The signed permit must be posted at the entry point so it is visible to everyone. After the entry is complete, the permit must be filed and kept for at least one year. An inspector who arrives on site and finds workers in a confined space without a posted, signed, current entry permit will issue orders immediately. This is one of the most commonly cited violations because employers either skip the permit entirely, use a stale permit from a previous entry, or fill it out after the work is already done.

The attendant: the person who saves your life by staying outside

O. Reg. 632/05 section 15 is unambiguous: a trained attendant must be stationed at the entry point of the confined space at all times while workers are inside. The attendant has four duties. First: monitor the entrants continuously. This means visual contact, voice communication, or an agreed signaling system — not checking in once every 20 minutes. Second: maintain an accurate count of who is inside the space. Third: remain at the entry point and never leave — not to get tools, not to answer a phone call, not to help with another task. Fourth: initiate the rescue plan immediately if an entrant is unresponsive, signals distress, or atmospheric monitoring alarms activate. The critical rule is that the attendant must never enter the confined space to attempt rescue. This is counterintuitive and emotionally difficult. When you see a co-worker collapse, every instinct says to go in and drag them out. But if the atmosphere knocked them unconscious, it will do the same to you in the same number of seconds. The attendant's job is to activate the mechanical retrieval system (tripod and winch), call for the rescue team, and call 911. Trained rescue personnel enter with supplied air breathing apparatus. Untrained rescuers enter with their lungs and become additional victims.

Equipment that keeps entrants alive

The minimum equipment for any confined space entry includes: a calibrated multi-gas monitor (4-gas minimum: O2, LEL, H2S, CO), mechanical ventilation sized for the space volume, a communication system that works in the space environment (two-way radio, hardwired intercom, or voice for short distances), a full body harness (CSA Z259.10) with a retrieval line attached to a mechanical device outside the space, and the mechanical retrieval device itself — typically a tripod with a self-retracting lifeline and winch, or a davit arm system. The retrieval system must be capable of non-entry rescue: pulling an unconscious, dead-weight worker vertically through the opening without anyone entering the space. For vertical entries (manholes, tanks with top-entry), a tripod positioned directly over the opening with a winch is standard. For horizontal entries, a davit or anchor point with a mechanical advantage system is used. Additional equipment depends on hazards present: SCBA or supplied air for IDLH atmospheres, lockout/tagout devices for energy isolation, electrical PPE for live conductor exposure, thermal protection for extreme temperatures, and fall arrest equipment for vertical drops inside the space.

The cost of non-compliance: fines, charges, and funerals

A Ministry of Labour inspector who finds workers in a confined space without proper procedures has the same enforcement tools as any OHSA violation — but confined space violations almost always result in the most severe response because the hazard is immediately life-threatening. Stop-work orders under OHSA section 57 are common: all work halts until every requirement of O. Reg. 632/05 is met. Fines on conviction reach $500,000 and up to 12 months imprisonment for an individual, $1,500,000 for a director or officer, and $2,000,000 for a corporation under OHSA section 66 (maximums raised by the Working for Workers amendments, current 2024). But the real consequences come after a fatality. Ontario has prosecuted employers, supervisors, and even co-workers after confined space deaths. Criminal Code section 217.1, added by the Westray Bill, establishes a duty for anyone directing work to take reasonable steps to prevent bodily harm. A confined space fatality where the employer failed to provide atmospheric testing, an attendant, or a rescue plan is a straightforward case for criminal negligence charges. In multiple Ontario cases, corporations have been fined hundreds of thousands of dollars after a single confined space death. Individual supervisors have received jail sentences. The cost of a proper confined space entry program — gas monitor ($1,500-$3,000), tripod and winch ($2,000-$4,000), training ($300-$500 per worker), and the time to fill out a permit — is negligible compared to a single fatality investigation, the legal costs, the WSIB claims, and the permanent weight of knowing that a worker died because you skipped the paperwork.

More Ontario safety tools: browse the WSIB & OHSA hub, or check fall-protection requirements and JHSC thresholds. Running crews on Ontario projects? ToolFluency for Ontario contractors keeps permits, timesheets, and job records in one place.