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Confined Spaces

What is a Confined Space?​

A confined space is an enclosed or partially enclosed space that:

  • Is not designed or intended for continuous human occupancy, AND
  • Has one or more of these characteristics:
    • Limited entry/exit
    • Unfavorable natural ventilation
    • Risk of harmful atmosphere
    • Risk of engulfment

Common Construction Confined Spaces:

  • Trenches/excavations (only if specific hazardous criteria met, not based on depth alone)
  • Tanks, vessels, silos
  • Pits, sumps, wells
  • Sewers, drains, culverts
  • Roof spaces with limited access
  • Tunnels and shafts
  • Bins and hoppers

[!warning] Confined Space Deaths Confined spaces kill workers quickly. Most deaths occur during attempted rescues by untrained persons.

Major Hazards​

Atmospheric Hazards​

Oxygen Deficiency:

  • Normal oxygen: 20.9%
  • Safe working level: 19.5-23.5%
  • < 19.5%: Drowsiness, unconsciousness, death
  • Causes: Consumption by chemical processes, displacement by other gases

Toxic Gases:

  • Carbon monoxide (CO) - colorless, odorless, deadly
  • Hydrogen sulfide (H₂S) - "rotten egg" smell, toxic
  • Sewer gases, chemical vapors

Flammable Atmospheres:

  • Methane, LPG, solvents
  • Risk of fire/explosion

Toxic Dusts/Fumes:

  • Welding fumes in enclosed spaces
  • Dust accumulation

Physical Hazards​

  • Burial by grain, sand, liquids
  • Can occur rapidly

Engulfment hazard showing bridging Figure: Example of 'bridging' which may result in engulfment

Entrapment:

  • Limited escape routes
  • Difficult rescue access

Temperature Extremes:

  • Heat stress in hot confined spaces
  • Hypothermia in cold/wet spaces

Other:

  • Noise, slips/trips, falling objects
  • Mechanical equipment

Identifying Confined Spaces​

Risk Assessment Required: Assess each space before entry to determine if it's a confined space.

Consider:

  • Is it enclosed/partially enclosed?
  • How many entry/exit points?
  • How quickly could atmosphere become hazardous?
  • What work will be done inside (might create hazards)?
  • Has space contained hazardous substances?

Decision flowchart to determine a confined space Figure: Flowchart for identifying a confined space

When is Confined Space Entry HRCW?​

Work in/near confined space is HRCW requiring SWMS.

Managing Confined Space Risks​

Hierarchy of Control​

Level 1: Elimination

Eliminate need to enter:

  • Remote inspection (cameras, drones)
  • Automation/robotics
  • Design changes

Example: Install tank with external manholes for cleaning instead of requiring internal entry.

Level 2: Minimize Risks if Entry Required

Engineering Controls:

Ventilation:

  • Forced ventilation to maintain safe atmosphere
  • Fresh air supply
  • Continuous operation during entry

Isolation:

  • Isolate from energy sources (electrical, mechanical, hydraulic)
  • Lockout/tagout
  • Blank off pipes (prevent ingress of substances)
  • Drainage to prevent flooding

Isolation using lockout and tags Figure: Example of tag and lockout isolation

Atmospheric Monitoring:

  • Continuous monitoring during entry
  • Test for oxygen, flammable gases, toxic gases
  • Calibrated instruments
  • Alarms if atmosphere unsafe

Access/Egress:

  • Improve access points where possible
  • Ensure rescue equipment can be used

Level 3: Administrative/PPE

Entry Permits:

  • Written authority to enter
  • Confirms controls in place
  • Authorizer signs permit

Training:

  • Confined space awareness
  • Emergency procedures
  • Equipment use

Standby Person:

  • Remains outside
  • continuously monitor the wellbeing of those inside the space
  • observe the work being carried out where practicable
  • Maintains communication
  • Raises alarm if needed
  • Does not enter for rescue

Standby person monitoring Figure: Standby person monitoring confined space with rescue equipment

Respiratory Protection:

  • Supplied-air respirators (continuous fresh air)
  • Self-contained breathing apparatus (SCBA) for IDLH atmospheres
  • NOT air-purifying respirators in oxygen-deficient spaces

Other PPE:

  • Full-body harness with retrieval line
  • Hard hat, gloves, boots
  • Protective clothing

Atmospheric Testing​

Before Entry:

  • Test atmosphere from outside
  • Test top, middle, bottom (gases stratify)
  • Only enter if safe

During Entry:

  • Continuous monitoring
  • Alarm if atmosphere changes
  • Exit immediately if unsafe

Atmospheric testing of remote regions Figure: Atmospheric testing of different levels (gases stratify)

Testing For:

  • Oxygen: 19.5-23.5% safe
  • Flammable gases: <5% of lower explosive limit (LEL)
  • Toxic gases: Below exposure standards (CO, H₂S, etc.)

Equipment:

  • Multi-gas detector (O₂, LEL, CO, H₂S minimum)
  • Calibrated and bump-tested
  • Alarms set correctly

Entry Permits​

Permit Must Specify:

  • Location and description of space
  • Purpose of entry
  • Duration of entry
  • Names of entrants, standby person, supervisor
  • Hazards identified
  • Control measures required
  • Atmospheric test results
  • Emergency contact numbers
  • Authorizer signature

Before Entry:

  • All control measures verified in place
  • All personnel briefed
  • Permit signed

During Entry:

  • Permit displayed at entry point
  • Valid for specified duration only
  • Cancelled if conditions change

Emergency Response and Rescue​

[!warning] Never Enter for Rescue Untrained, unequipped rescue attempts kill more people than the original incident. DO NOT ENTER.

Requirements:

Rescue Plan:

  • Specific to confined space
  • Method to retrieve without entry (preferred)
  • Rescue equipment identified
  • Trained rescue personnel or emergency services
  • Regular drills

Retrieval Equipment:

  • Full-body harness on entrant
  • Retrieval line attached
  • Mechanical retrieval winch (can lift unconscious person)
  • Available for immediate use

Communication:

  • Constant communication between entrant and standby person
  • Method: visual, verbal, radio, rope signals
  • Standby person raises alarm immediately if communication lost

If Emergency:

  1. Standby person raises alarm
  2. Calls emergency services (000)
  3. Attempts non-entry rescue if safe (use retrieval line/winch)
  4. Does NOT enter confined space
  5. Provides information to emergency responders

Practical Example​

Scenario: Inspecting inside concrete water tank (empty, 3m deep)

Before Entry​

Identify: Confirmed confined space (enclosed, limited exit, unfavorable ventilation)

Assess Hazards:

  • Oxygen deficiency (enclosed space)
  • Slip hazard (wet surfaces)
  • Limited access (single manhole 600mm diameter)

Controls Implemented:

Engineering:

  • Forced ventilation (blower supplying fresh air)
  • Continuous atmospheric monitoring (O₂, LEL, CO)
  • Tank isolated (valves locked shut, tagged)
  • Lighting installed

Administrative:

  • Entry permit prepared and authorized
  • Entrant and standby person briefed
  • Emergency services notified (on standby)

PPE:

  • Full-body harness with retrieval line
  • Supplied-air respirator (continuous fresh air supply)
  • Hard hat, gloves, non-slip boots

During Entry​

  • Atmospheric test: O₂ 20.8%, LEL 0%, CO 0 ppm ✓
  • Standby person positioned at entry
  • Communication maintained (verbal through manhole)
  • Continuous monitoring (alarm if atmosphere changes)
  • Inspection completed in 20 minutes
  • Entrant exits safely

Result​

Safe entry and exit. Continuous monitoring and standby person provided safety net.