What is a Confined Space?
A Confined Space is an enclosed or partially enclosed space that is not designed or intended for human occupancy, has restricted means of entry or exit, and presents specific risks to health and safety from atmospheric hazards, engulfment, or other dangers. Confined space work represents one of the highest-risk activities in Australian workplaces and requires rigorous controls under Part 4.3 of the WHS Regulations.
The Three-Part Definition
Under Regulation 5 of the Model WHS Regulations and Australian Standard AS 2865:2009, a space only qualifies as a confined space if it meets all three criteria simultaneously.
| Criterion | Description | Examples |
|---|---|---|
| Enclosed or Partially Enclosed | Physical boundaries restrict natural air movement and ease of entry/exit | Tanks (fully enclosed), trenches or vats (partially enclosed) |
| Not Designed for Human Occupancy | The space was built to hold substances or equipment, not people | Sewer pipes, fuel tanks, grain silos, pump stations |
| Specific Risk Factors | Unsafe oxygen levels (below 19.5% or above 23.5%), contaminants, or engulfment hazards | Oxygen-deficient atmospheres, toxic gases (H2S, CO), free-flowing solids (grain) |
A space that fails to meet any one criterion is not a confined space under the regulations. However, it may still be a "restricted space" requiring other safety controls under general WHS duties.
Atmospheric Hazards: The Invisible Killers
Atmospheric hazards account for the majority of multiple-fatality incidents in confined spaces. Unlike mechanical hazards, these dangers are often invisible, odourless, and strike without warning.
Oxygen Deficiency occurs when oxygen levels fall below the safe range of 19.5% to 23.5%. The body does not detect low oxygen—it detects high carbon dioxide. A worker entering a nitrogen-purged tank may lose consciousness within seconds without any sensation of breathlessness. At oxygen levels below 6%, death occurs within minutes.
Flammable Atmospheres exist when gas concentrations exceed 5% of the Lower Explosive Limit (LEL). Entry is prohibited above 10% LEL, and immediate evacuation is required. Common culprits include methane in sewers and petrol vapours in transport tankers.
Toxic Contaminants like Hydrogen Sulfide (H2S) and Carbon Monoxide (CO) pose lethal threats at low concentrations. H2S, produced by decaying organic matter in sewers and manure pits, causes "olfactory fatigue" at concentrations above 100 ppm—paralysing the sense of smell and removing the warning sign. High concentrations cause immediate respiratory paralysis.
WorkSafeKit's permit system ensures atmospheric testing is recorded, standby persons are assigned, and emergency procedures are verified before every confined space entry.
Regulatory Requirements Under WHS Regulation 48
Part 4.3 of the Model WHS Regulations (Regulation 48 in Victoria) imposes strict requirements on Persons Conducting a Business or Undertaking (PCBUs).
The Hierarchy of Controls must be applied. The first step is always elimination—designing out the need for entry entirely using remote inspection technology, external cleaning systems, or sight glasses. Where entry cannot be eliminated, risks must be minimised through isolation (blanking pipes, lock-out/tag-out), forced ventilation, and engineering controls.
Entry Permits are mandatory for every entry under Regulation 67. A competent person must issue a written permit specifying the space, authorised personnel, timeframe, atmospheric test results, isolation procedures, required PPE, and emergency arrangements. The permit is a legal authorisation, not a checklist. If a notifiable incident occurs, the permit must be retained for at least two years.
Atmospheric Testing must follow a specific sequence due to sensor physics. Oxygen is tested first (most LEL sensors require oxygen to function correctly), then flammables, then toxic gases. Testing must be conducted from outside the space, at multiple levels, as gases stratify—methane rises, carbon monoxide mixes, and hydrogen sulfide settles at the bottom.
The Standby Person is a safety-critical role. This person must maintain continuous contact with entrants, monitor gas detector readings, prevent unauthorised access, and raise the alarm in emergencies. Critically, the standby person must never enter the space to attempt a rescue unless they are part of a trained rescue team with proper breathing apparatus.
Emergency Rescue and the Platinum Ten Minutes
A grim statistic defines confined space rescue: approximately 60% of confined space fatalities are would-be rescuers who enter without proper equipment and training. The "Platinum Ten Minutes" refers to the time window before brain death from asphyxiation—shorter than most fire brigade response times.
Regulation 74 requires PCBUs to establish rescue procedures and ensure rescue capability is available on site. Relying solely on calling emergency services (000) is generally non-compliant for immediately dangerous to life or health (IDLH) environments.
The preferred method is non-entry rescue. The entrant wears a full-body harness connected to a mechanical retrieval system (tripod and winch). If an emergency occurs, the standby person winches the victim out without entering the hazard zone. This requires the right equipment and regular practice drills to ensure the system works when seconds count.
Track confined space entries, monitor permit compliance, and maintain rescue drill records with WorkSafeKit's integrated safety management platform.
Industry-Specific Risks
| Sector | Common Confined Spaces | Primary Hazards |
|---|---|---|
| Agriculture | Grain silos, water tanks, manure pits | Engulfment in grain; H2S and methane from manure fermentation; oxygen displacement by CO2 |
| Construction | Deep trenches, lift wells, drainage pipes | Soil gases (H2S); CO from generators; trench collapse; groundwater inrush |
| Manufacturing | Pressure vessels, boilers, storage vats | Chemical residues; nitrogen purging causing asphyxiation; heat stress |
| Utilities | Sewers, valve pits, storm drains | Hydrogen sulfide ("sewer gas"); methane (explosion); flash flooding |
| Transport | Road tankers, rail cars, shipping containers | Residual chemicals; volatile organic compounds; fumigants (phosphine) |
Frequently Asked Questions
What's the difference between a confined space and a restricted space?
A restricted space has difficult entry or exit but lacks the specific atmospheric or engulfment hazards required for confined space classification. While it doesn't require a full confined space permit, it still needs a risk assessment and Safe Work Method Statement. A restricted space can become a confined space—for example, a plant room becomes a confined space if someone operates a petrol generator inside, introducing carbon monoxide.
Can workers enter briefly without a full permit?
No. The regulations apply to any entry, regardless of duration. Many fatalities occur during brief, informal entries where workers underestimate the risk. Even a "quick look" requires proper hazard identification, atmospheric testing, and controls.
What training is required for confined space work?
Workers must be trained and competent in hazard recognition, atmospheric testing, emergency procedures, and equipment use. While there's no government-issued licence, industry typically relies on units like RIIWHS202E (Enter and work in confined spaces) from the RII training package. Refresher training is recommended every two years to maintain competency, and rescue drills should be conducted regularly to ensure procedures work in practice.
Why is gas testing done in a specific order?
Testing must follow the sequence of oxygen first, then flammables, then toxics. Most catalytic bead sensors used for LEL detection require oxygen to function—if oxygen is low, the LEL reading may be falsely low, creating a dangerous illusion of safety. Testing must also be conducted at multiple levels because gases stratify by density.
References and Further Reading
- Safe Work Australia: Confined Spaces Code of Practice
- Model Work Health and Safety Regulations (Part 4.3)
- WorkSafe Victoria: Confined Spaces
- Australian Standard AS 2865:2009 - Confined spaces