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Confined space study guide: key rules on all 11 topics

Free Confined Space study guide: 172 key points from the Guideline for working in confined spaces (Ontario) in plain words, organised by topic, each topic linked to its practice questions.

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This study guide collects our notes on every topic of the Confined Space Entry Awareness Test — Canada on one page: 172 short points in our own words, grouped by topic and by handbook section. Read it from top to bottom before your first practice test, or jump to a topic from the list below.

Each topic ends with a link to its practice questions, so you can check what you just read straight away, and a link to the official chapter for the full wording. The notes summarise the Guideline for working in confined spaces (Ontario) from the Ontario Ministry of Labour, Immigration, Training and Skills Development — Confined Spaces Regulation (O. Reg. 632/05) and guideline; they do not replace it, and where our notes and the official source differ, the official source wins.

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What is a confined space

The legal definition in Ontario and B.C., continuous human occupancy, examples from tanks to manholes, when entry begins, and why so many deaths are would-be rescuers.

Practise What is a confined space questionsFlashcardsOfficial chapter

definition

  • A confined space is a fully or partially enclosed space that is not both designed and constructed for continuous human occupancy, and in which atmospheric hazards may occur because of its construction, location, contents or the work done in it.
  • Both conditions must apply: a space designed and built for continuous occupancy (an office, control room, walk-in freezer, mechanical room) is not a confined space even if a hazard could occur.
  • The regulation applies to all workplaces covered by the Occupational Health and Safety Act, except underwater diving work; firefighters doing emergency work are exempt from most sections but must still be protected.
  • "Related work" means work done near a confined space in direct support of the work inside it.

Confined spaces

  • To decide, ask three questions: is the space fully or partially enclosed; is it not both designed and constructed for continuous human occupancy; might an atmospheric hazard occur?
  • Examples that are not designed for continuous occupancy: storage tanks, tank cars, process vessels, boilers, vats, bins, silos, pits, pump wells, sewers, pipes, ducts, flues, ovens and chimneys.
  • Entry occurs as soon as any part of a person's body breaks the plane of the opening.
  • The regulation does not apply to openings too small for a person's body to pass through, but the general duty to take every reasonable precaution still applies.
  • Controlling a hazard (for example with ventilation) does not stop a space from being a confined space; only eliminating the possibility of an atmospheric hazard does.

B.C. definition

  • In B.C. a confined space is enclosed or partly enclosed, not designed or intended for continuous human occupancy, has limited or restricted entry or exit that may complicate first aid, evacuation or rescue, and is large enough for a worker to enter to do assigned work.

Confined Space: Introduction

  • All Canadian jurisdictions have confined space regulations; the details vary slightly.
  • An estimated 60 % of confined space deaths are among would-be rescuers.
  • A confined space is not necessarily small and may be above or below ground.
  • Further examples: hoppers, utility vaults, water towers, manholes, digesters, manure pits, truck or rail tank cars, aircraft wings, shipping containers, fish holds; ditches, wells and trenches can be confined spaces when access is limited.
  • Treat every confined space as hazardous unless a competent person has determined otherwise.
  • First ask whether the work really must be done inside; in many fatal cases it could have been done from outside.

Atmospheric and other hazards

Oxygen deficiency and enrichment, toxic gases such as hydrogen sulphide and carbon monoxide, simple asphyxiants, where hazards come from, engulfment and physical hazards.

Practise Atmospheric and other hazards questionsFlashcardsOfficial chapter

atmospheric hazards

  • Atmospheric hazards are: an accumulation of flammable, combustible or explosive agents; oxygen below 19.5 % or above 23 % by volume; or an accumulation of gases, vapours, fumes, dusts or mists that could cause acute, life-threatening effects or stop a person from escaping unaided.
  • "Escape unaided" means escaping without respiratory protection, emergency equipment or help from others.

oxygen

  • Normal air has about 21 % oxygen; 19.5 % is the minimum for safe entry.
  • About 16 %: impaired judgement and breathing; about 14 %: faulty judgement and rapid fatigue; about 6 %: difficult breathing and death within minutes.
  • Above 23 %: oxygen-enriched, an extreme fire hazard; enrichment can come from leaking oxygen lines or welding equipment.
  • Oxygen deficiency is a leading cause of confined space deaths; rusting (oxidation) inside a tank can use up oxygen, and other gases can displace it.

sources of atmospheric hazards

  • Previous contents, such as solvent residue left in a tank.
  • Chemical or biological reactions: decaying organic matter can produce methane (flammable) and hydrogen sulphide (toxic).
  • Work done in or near the space: welding fumes, solvent vapours from cleaning.
  • Contaminants from nearby, such as vehicle exhaust (carbon monoxide) entering a manhole or trench.

Confined Space: Introduction, hazards

  • Toxic gases such as hydrogen sulphide and carbon monoxide can make a worker ill or unconscious.
  • Simple asphyxiants such as nitrogen, argon and carbon dioxide displace oxygen; unconsciousness or death can follow within minutes.
  • Other hazards: fire and explosion, residual chemicals, release from supply lines, noise, heat, cold, poor lighting, moving parts, engulfment in shifting bulk material, flooding, slips and falls, traffic, and biological hazards such as bacteria in sludge.
  • Confined spaces are more dangerous because exits are limited, self-rescue and rescue are harder, natural air movement is poor, conditions can change quickly, and work can create new hazards.

Program, hazard assessment and plan

The written program, the signed hazard assessment, the plan written by a competent person, co-ordination when several employers share a space, and the hierarchy of controls.

Practise Program, hazard assessment and plan questionsFlashcardsOfficial chapter

program

  • If workers may enter a confined space, the employer must have a written program before anyone enters.
  • The program covers how confined spaces are recognized, how hazards are assessed, how plans are developed, how workers are trained, and an entry permit system.
  • Outside construction projects, the program is developed with the joint health and safety committee (JHSC) or health and safety representative, who also gets a copy.

assessment

  • Before any worker enters, an adequate hazard assessment must be done and recorded in writing.
  • It considers hazards from the space's design, construction, location, use or contents, and hazards that may develop during the work.
  • It is done by a person with adequate knowledge, training and experience, whose qualifications the employer records; the person names, signs and dates the assessment.
  • Similar spaces with the same hazards may share one assessment document if each space is identified.
  • The assessment is reviewed as often as needed to keep the plan adequate.

plan

  • Before entry, an adequate written plan with procedures to control the hazards must be developed and implemented by a competent person.
  • The plan covers worker duties, co-ordination, on-site rescue, rescue equipment and communication, PPE, isolation of energy, attendants, entry and exit, atmospheric testing, flammable substances, and ventilation and purging.

several employers

  • If workers of more than one employer work in the same confined space, the lead employer (or the constructor on a project) prepares a co-ordination document before anyone enters.

roles

  • A person with adequate knowledge, training and experience carries out the assessment, conducts general training, inspects rescue equipment and PPE, and performs atmospheric tests.

Confined Space: Program and Introduction

  • Hierarchy of controls: elimination (do the job without entering), substitution (cold work instead of hot work), engineering controls (mechanical ventilation), administrative controls (entry permit system), and PPE last.
  • The program should be reviewed when circumstances change and at least once a year.

Entry permits

What an entry permit must contain, issuing a separate permit for each entry, checking it before every shift, and keeping a record of entries and exits.

Practise Entry permits questionsFlashcardsOfficial chapter

entry permits

  • A separate entry permit is issued each time work is to be done in a confined space, before any worker enters.
  • The permit includes at least: the location; a description of the work; the hazards and control measures; the time period it covers; the attendant's name; a record of each worker's entries and exits; the entry and rescue equipment with verification that it works; atmospheric test results; and hot-work provisions if hot work is planned.
  • Before each shift, a competent person verifies that the permit complies with the plan.
  • The permit must be readily available to everyone who enters or does related work while it is in force.

Entry permit

  • The permit communicates the hazards and controls to workers before entry.
  • Ontario law does not require a signature or posting at the entrance, but a signature is good due diligence and everyone must know where the permit is.
  • The entry and exit record is not meant for every brief step out to grab a tool; the method is set in the program.
  • Each confined space needs its own permit, even if spaces are similar.

Confined Space: Program

  • The entry permit is an administrative tool; it should be filled out by someone fully trained and experienced in confined space work.
  • Typical contents also include the names of the entrants, the attendant and the supervisor, date and time of entry and expected exit, calibration date of the monitor, communication method and emergency plan.
  • The supervisor's signature certifies that the space has been evaluated, prepared and is safe to enter.
  • CCOHS recommends posting the permit at the space until the work is done and keeping a copy on file.
  • Record the time of exit on the permit when leaving; never close up a space until it is confirmed that no one is inside.

Atmospheric testing

Who tests, with what instruments, when to test and re-test, recording results, continuous monitoring and B.C.'s 20-minute pre-entry rule.

Practise Atmospheric testing questionsFlashcardsOfficial chapter

atmospheric testing

  • The employer appoints a person with adequate knowledge, training and experience to test as often as necessary before and while a worker is inside.
  • If the space has been both unoccupied and unattended, test before anyone enters or re-enters.
  • Use calibrated instruments in good working order, suited to the hazards in the assessment.
  • Record the result of every sample; with continuous monitoring, record results at adequate intervals.
  • Test in a way that does not endanger the tester. A "sample" is one reading; a "test" is a set of samples.

Atmospheric testing

  • Continuous monitoring is required for hot work where flammable gas or vapour is or may be present, when the space has been made inert, and when the plan calls for it.
  • Sample representatively: gases can layer (stratify) and form pockets.
  • Data logging does not replace recording results at the intervals in the plan.
  • A combustible gas meter calibrated to one gas (for example pentane) reads other gases differently; results need a knowledgeable person to interpret them.
  • Decision order: oxygen 19.5–23 %, then flammables (LEL), then toxic substances.

Introduction and Atmospheric Testing

  • Test from outside the space before entry, side to side and top to bottom, using remote probes and sampling lines.
  • Test for oxygen (too little and too much), flammable or explosive gases, and toxic gases.
  • Calibrate and bump-test instruments as the manufacturer directs, ideally just before each use.
  • Record results and the instrument used on the entry permit.
  • If a worker leaves for a short time (a coffee break), re-test before re-entry unless continuous monitoring readable from outside covered the absence.
  • If a monitor alarms, leave the space immediately.

WorkSafeBC OHS Regulation ss. 9.25–9.26

  • Pre-entry testing must be completed not more than 20 minutes before a worker enters.
  • If all workers have been out for more than 20 minutes, test again before re-entry.
  • In moderate or high hazard atmospheres, test as needed while workers are inside; monitor continuously if an atmosphere above 20 % of the LEL could develop.
  • Tests are done by a qualified person; the record shows the date, time, tester's initials and the levels found, and results are posted at every entry point.

Flammable atmospheres and hot work

Lower explosive limits for inspection, cold work and hot work, combustible dust, oxygen enrichment, inerting, and the conditions for hot work in a confined space.

Practise Flammable atmospheres and hot work questionsFlashcardsOfficial chapter

flammable and explosive substances

  • "Hot work" can produce a source of ignition; "cold work" cannot.
  • No one may enter or stay in a space where airborne combustible dust or mist could create an explosion hazard.
  • With flammable gas or vapour possibly present, entry is allowed only if, measured with a combustible gas instrument:
  • inspection work producing no ignition source: below 25 % of the lower explosive limit (LEL);
  • cold work: below 10 % of the LEL;
  • hot work: below 5 % of the LEL, oxygen not above 23 %, continuous monitoring, hot-work provisions on the permit, and a warning system and exit procedure if 5 % LEL or 23 % oxygen is exceeded.
  • These limits are achieved by ventilation, purging, making the atmosphere inert or other adequate means.
  • An inerted space must be continuously monitored, and entrants need respiratory protection, equipment that lets people outside locate and rescue them, and other necessary equipment, all inspected beforehand.

Hot work

  • Hot work examples: welding, cutting, grinding, non-explosion-proof electrical equipment. Cold work examples: valve adjustment, brush painting.
  • Hot work in a space with no flammable gas, vapour or dust is allowed once all normal confined space measures are in place.
  • Build in a safety margin so the alarm warns before the limits are reached.

Introduction, fire and explosion

  • Remove flammable gases, liquids and vapours before hot work; clean or shield surfaces coated with combustible material.
  • Do not bring fuel containers such as gasoline or propane into the space if possible.
  • Use spark-resistant tools where appropriate and make sure equipment is bonded or grounded.
  • Never add oxygen to "freshen" the air: enrichment greatly increases fire and explosion risk.
  • Inerting (filling the space with nitrogen, argon or carbon dioxide) removes the fire hazard but creates an oxygen-deficient atmosphere.

Ventilation and purging

Purging versus ventilating, mechanical and natural ventilation, alarms for ventilation failure, why pure oxygen is never used, and respirators when ventilation is not practical.

Practise Ventilation and purging questionsFlashcardsOfficial chapter

ventilation and purging

  • If oxygen or toxic-contaminant hazards exist or are likely, the space must be purged, ventilated or both before entry, so acceptable levels are kept while workers are inside.
  • If mechanical ventilation is needed, there must be a warning system and exit procedure for ventilation failure.
  • If purging or ventilating is not practical for technical reasons, entrants use respiratory protection, equipment to be located and rescued, and other necessary equipment, inspected before entry.

Ventilation and purging

  • Purging removes contaminants by displacing them (for example blowing air into a space that held toxic gas); ventilation is the continuous supply of fresh air by mechanical means while work goes on.
  • Ventilation must continue during the work to keep oxygen acceptable, protect against releases, remove contaminants made by the work, or cool the space.
  • Keep supply and exhaust points as far apart as possible; provide openings for clean replacement air.
  • Never use pure oxygen to ventilate a confined space.
  • A ventilation-failure alarm should be triggered by loss of airflow (a flow or pressure switch in the air stream), not only by motor failure, so a broken fan belt or blocked duct still sets it off.

Introduction

  • Natural air currents are usually not reliable; mechanical ventilation (blowers, fans) is usually needed.
  • Make sure supplied air is clean and reaches the whole space; pockets of gas can remain.
  • Exhaust air away from workers outside; note mechanical ventilation on the permit.

WorkSafeBC OHS Regulation ss. 9.27–9.33

  • When practicable, the space should contain clean respirable air: about 20.9 % oxygen, no measurable flammable gas, and contaminants below 10 % of exposure limits.
  • Natural ventilation must not be relied on in a high hazard atmosphere or if it could draw in unclean air; its airflow must be monitored if used.

Isolation, lockout and engulfment

Blanking or disconnecting piping, double block and bleed, why closing a valve is not enough, locking out electrical and moving equipment, and free-flowing materials.

Practise Isolation, lockout and engulfment questionsFlashcardsOfficial chapter

isolation of energy and control of materials

  • Protect entrants from hazardous substances entering the space by blanking or disconnecting piping; other adequate means only if that is not technically practical.
  • Protect from electrical energy by disconnecting, de-energizing, locking out and tagging the source.
  • Protect from moving parts by disconnecting, de-energizing, locking out and tagging the equipment, or by blocking it if that is not practical.
  • Protect from drowning, engulfment, entrapment and suffocation by free-flowing material by adequate means.

Isolation

  • Blanking means inserting a solid metal plate (a blank) between pipe flanges; disconnecting means removing a section of pipe.
  • Other adequate means can include a double block and bleed system or an engineered freeze plug.
  • A single closed valve is not adequate against toxic substances or materials that could drown or engulf a worker.
  • Locking out isolating valves is a reasonable extra precaution.
  • Properly guarded equipment (for example a guarded fan) may not need to be de-energized, unless flammable agents could accumulate.

WorkSafeBC OHS Regulation s. 9.1 and ss. 9.19–9.21

  • Double block and bleed: two locked-out closed valves with a drain or vent locked open between them.
  • A blind is a solid plate on the end of a disconnected pipe; blanks and blinds must withstand the line's maximum pressure.
  • The bleed must stay clear; check it within 20 minutes before entry if not monitored automatically.

Introduction

  • De-energize and lock out all hazardous energy (electrical, mechanical, hydraulic, pneumatic, chemical, thermal) before entry.
  • Physically disconnect pipes or bolt isolation blanks in place; closing valves is not sufficient.
  • Remove liquids and free-flowing solids, or put a barrier in place, to prevent drowning or engulfment.
  • Make sure no work outside the space can affect safety or air quality inside.

The attendant (standby person)

Where the attendant stands, constant communication, never entering the space, summoning rescue, and B.C.'s standby rules for low, moderate and high hazard atmospheres.

Practise The attendant (standby person) questionsFlashcardsOfficial chapter

attendant

  • Whenever a worker enters a confined space, an attendant is assigned and stationed outside, near the entrance (or the entrance that best lets them do the job).
  • The attendant is in constant communication with everyone inside using the method in the plan, and has a device to summon an adequate rescue response.
  • The attendant must not enter the confined space at any time.
  • The attendant monitors the safety of workers inside, assists them, and summons rescue if needed.
  • The attendant's name is recorded on the entry permit.

Roles and On-site rescue

  • The attendant is trained in confined space hazards; their primary job is to monitor and assist entrants (communication, calling rescue, passing in fresh-air packs and PPE).
  • During a rescue the attendant stays at the entrance; they may join the rescue team only if another person trained in attendant duties replaces them.

Confined Space: Program

  • The attendant (safety watch or standby) knows the hazards and can recognize signs and symptoms in entrants.
  • They stay outside and do no other work that would interfere with monitoring.
  • They keep two-way communication, order immediate evacuation if an uncontrolled hazard appears, and call emergency help at once.
  • They provide non-entry assistance and enter for rescue only with the strictest precautions and after another attendant takes over.

WorkSafeBC OHS Regulation ss. 9.34–9.36 (B.C. standby person)

  • Low hazard atmosphere: a standby person is assigned, can be summoned continuously, checks on entrants at least every 20 minutes, and can summon rescue immediately.
  • Moderate hazard atmosphere: the standby person is at or near the entrance and checks at least every 20 minutes.
  • High hazard atmosphere, engulfment or entrapment: the standby person is at the entrance, continuously monitors entrants, is equipped to rescue with lifting equipment, and prevents lifelines from tangling.

Rescue and emergencies

Written on-site rescue procedures, trained rescuers, why 911 is not a rescue plan, rescuing from outside, breathing air for rescuers, drills and notifying rescue services.

Practise Rescue and emergencies questionsFlashcardsOfficial chapter

rescue

  • No worker enters or stays in a confined space unless written on-site rescue procedures are ready for immediate use.
  • Before entry, enough people must be available who are trained in the on-site rescue procedures, first aid and CPR, and the use of the rescue equipment in the plan.
  • Rescue equipment must be readily available, suitable for entering the space, and inspected (with a written record) by a person with adequate knowledge, training and experience.
  • The employer sets communication methods suited to the hazards so entrants can reach the attendant.

On-site rescue procedures and equipment

  • Calling 911 is not an on-site rescue procedure; emergency services do not replace the employer's duty.
  • Rescue may be contracted out only if it allows a timely response; the employer remains responsible.
  • Not every rescuer needs all three kinds of training, as long as the team as a whole has them.
  • Equipment examples: harnesses and lifelines, hoist or retrieval systems, self-contained breathing apparatus (SCBA), airline respirators; it must fit through the space's openings.
  • One rescue team busy at one space is not available for another; plan for simultaneous entries.

Confined Space: Program

  • More than 60 % of confined space deaths are would-be rescuers who were not trained and equipped.
  • Rescue from outside the space when possible; no one enters to rescue unless trained in the procedures and wearing proper protective equipment.
  • Rescuers must not breathe the same air as the victim; use SCBA or a supplied-air respirator with an escape bottle.
  • An attendant stays outside to monitor during the rescue.
  • Practise rescue procedures frequently.

WorkSafeBC OHS Regulation ss. 9.37–9.39

  • The employer must provide rescue services; if another company or a fire department provides them, there must be a written agreement.
  • Rescue persons must be equipped and trained, with a practice drill at least once a year and records kept.
  • The supervisor or standby person notifies rescue personnel before entry and again when everyone has left.

Training, access and records

Hazard-recognition and plan-specific training, annual review, entry and exit openings, preventing unauthorized entry, protective equipment and how long records are kept.

Practise Training, access and records questionsFlashcardsOfficial chapter

training

  • Every worker who enters a confined space or does related work gets adequate training in recognizing confined space hazards and in safe work practices, plus training on the specific plan.
  • General training is given by a person with adequate knowledge, training and experience and, outside projects, developed with the JHSC or representative.
  • Outside projects, training is reviewed at least once a year and whenever circumstances change.
  • Written records show who gave and who received the training, what it covered and when; they may be kept on the entry permit.

Training

  • Attendants and rescue workers need training too, even though they do not enter.
  • Hands-on training with the equipment and PPE should be part of the course; new workers can be teamed with experienced ones.
  • A yearly review is not the same as yearly retraining, but refresher training may be needed.
  • There is no government certification for confined space trainers, workers or programs in Ontario; the employer must make sure training is adequate.
  • Purchased or web-based general training may need to be supplemented with plan-specific training.

PPE, access, unauthorized entry, records

  • Each entrant gets adequate personal protective equipment, clothing and devices under the plan.
  • An adequate means of entering and exiting is provided for all entrants.
  • Where unauthorized entry is possible, each entrance is secured or has barricades, warning signs or both.
  • Outside projects, assessments, plans, training records, permits, equipment inspections and test results are kept for one year or long enough to keep the two most recent records of each kind; on projects, they are kept for one year after the project ends.

Means of entering and exiting

  • Secure ladders or other suitable means should give ready entry and exit.
  • A manhole of at least 24 inches (about 61 cm) in diameter is recommended as the minimum safe opening; hinged covers should lock open.
  • Opening size must be considered when choosing PPE and rescue equipment.
  • A cover that needs a tool to remove may be considered secured against entry.

Program

  • Training covers hazards, controls, equipment such as blowers, gas monitors and lockout devices, PPE such as harnesses and respirators, communication and retrieval systems, emergency procedures, first aid and CPR, and the specific task.

Written in our own words from: Guideline for working in confined spaces (Ontario)

FAQ

Confined Space study guide: common questions

What is the best way to use this Confined Space study guide?

Read one topic, then answer that topic's practice questions while the rules are fresh. Note the questions you miss, re-read those notes, and finish with a full practice test across all 11 topics.

Is this the official Confined Space handbook?

No. It is our own summary of the Guideline for working in confined spaces (Ontario). Use it to review, and use the official handbook when you need the exact wording of a rule.

Can I print the study guide?

Yes, with your browser's print command. For practice questions on paper with an answer key, use our printable questions and answers page instead.

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