9.3 Confined Space Entry, Atmospheric Testing & Emergency Protocols (GSR 5)
Key Takeaways
General Safety Regulation 5(1) allows entry only after the air has been tested and evaluated by a competent person who certifies in writing that the space is and will remain safe.
Under GSR 5(2), where oxygen is or may be below 20% by volume or a hazardous gas, vapour, dust or fumes may be present, the space must be purged and ventilated and isolated by blanking (or locked valves where blanking is impracticable).
Where a safe atmosphere cannot be achieved, GSR 5(3) requires approved breathing apparatus, a harness and rope, and at least one person trained in resuscitation stationed outside the entrance.
GSR 5(5) limits flammable concentrations to 25% of the lower explosive limit where the work creates no ignition source, and 10% for other work.
CR 13(2)(j) applies the GSR confined-space precautions to anyone entering an excavation, and CR 20(7) to anyone entering a silo; attendants should start non-entry rescue rather than enter unprotected.
1. The Legal Framework: General Safety Regulation 5
Confined spaces kill quickly and often kill more than one person, because would-be rescuers enter without protection and are overcome by the same atmosphere. On construction sites, confined spaces include manholes and junction chambers, sewer and stormwater connections, valve and meter pits, pump sumps, caissons and pile casings, tanks and silos, box girders and hollow abutments, and some excavations.
The governing rule is General Safety Regulation 5 (GSR 5), "Work in confined spaces". The Construction Regulations apply it in two places: CR 13(2)(j) requires the GSR confined-space precautions to be complied with by any person entering any excavation, and CR 20(7) requires them when entering any silo of a bulk mixing plant. Regulation 1 of the General Safety Regulations defines a confined space as an enclosed, restricted or limited space in which, because of its construction, location or contents, or any work done in it, a hazardous substance may accumulate or an oxygen-deficient atmosphere may occur. It expressly includes any chamber, tunnel, pipe, pit, sewer, container, valve, pump, sump or similar construction, equipment or object in which a dangerous liquid or a dangerous concentration of gas, vapour, dust or fumes may be present. Engulfment by loose material is a further hazard in silos, hoppers and trenches.
2. What GSR 5 Requires
GSR 5(1) – Testing and certification: the employer or user of machinery must ensure that a confined space is entered only after the air has been tested and evaluated by a person competent to pronounce on its safety, who has certified in writing that the space is safe and will remain safe while anyone is inside, taking into account the nature and duration of the work.
GSR 5(2) – Where that cannot be done: where a confined space contains or is likely to contain a hazardous gas, vapour, dust or fumes, or has or is likely to have less than 20% oxygen by volume, it may be entered only when:
- (a) it has been purged and ventilated to provide a safe atmosphere, and measures to maintain that atmosphere have been taken; and
- (b) it has been isolated from all pipes, ducts and other communicating openings by effective blanking (not merely shutting or locking a valve), or, where blanking is not practicable, all valves and cocks that could be a source of danger have been locked and secured with chains and padlocks.
GSR 5(3) – Breathing apparatus entry: where purging and ventilation (5(2)(a)) cannot achieve a safe atmosphere, entry is allowed only with breathing apparatus of a type approved by the Chief Inspector, and:
- the isolation in 5(2)(b) is in place;
- each entrant wears a safety harness or similar equipment with a rope reaching beyond the access point, the free end of which is tended by the attendant;
- at least one other person trained in resuscitation remains immediately outside the entrance to assist or remove anyone; and
- approved breathing and resuscitation apparatus is available immediately outside the space.
GSR 5(4): everyone must leave the space when the work is completed.
GSR 5(5) – Flammable atmospheres: where the gas, vapour, dust or fumes are explosive or flammable, the space may be entered only if the concentration does not exceed 25% of the lower explosive limit (LEL) where the work creates no source of ignition, or 10% of the LEL where other work (including hot work or spark-producing tools) is done.
GSR 5(6): the same rules apply to work immediately outside a confined space where a dangerous atmosphere may occur because of its proximity.
3. Atmospheric Hazards
| Hazard | Typical construction source | Behaviour | GSR / HCA benchmark |
|---|---|---|---|
| Oxygen deficiency | Rusting steel, organic decay, displacement by inert gas or CO2 | Can occur anywhere in the space | GSR 5(2): below 20% by volume triggers purging, isolation or breathing apparatus |
| Hydrogen sulphide (H2S) | Sewers, sludge, organic ground | Heavier than air (relative density about 1.19); collects low; deadens the sense of smell at higher concentrations | HCA OEL: 2 ppm 8-h TWA, 10 ppm STEL |
| Carbon monoxide (CO) | Engines, generators and pumps near openings | About the same density as air; mixes through the space | HCA OEL: 50 ppm 8-h TWA |
| Methane and other flammables | Sewers, landfill, leaking gas mains, solvent coatings | Methane lighter than air (collects high); solvent vapours usually heavier | GSR 5(5): 25% LEL (no ignition) / 10% LEL (other work); methane LEL about 5% by volume |
| Engulfment | Loose material in silos, trenches and hoppers | Can bury entrants | Physical controls and isolation of feed |
Never ventilate a confined space with pure oxygen: oxygen enrichment makes clothing, hair and grease burn violently. Use fresh air only.
4. The Entry Permit System
GSR 5 does not use the word "permit", but the written certification in GSR 5(1) is normally delivered through a confined space entry permit issued by an authorised person. A typical permit records:
- the space, the task, the duration and the entrants;
- isolation: blanking or locked valves (GSR 5(2)(b)), and lockout of pumps, agitators and electrical equipment;
- cleaning and purging, where the space has held liquids or gases;
- atmospheric test results with time, instrument and tester (GSR 5(1));
- ventilation arrangements and the breathing apparatus required, if any;
- the attendant and rescue arrangements (GSR 5(3)(b)–(d));
- sign-off by the issuer, attendant and entrants, valid for one shift and void if conditions change.
5. Atmospheric Testing in Practice
- Use an intrinsically safe multi-gas detector measuring oxygen, flammables (% LEL), carbon monoxide and hydrogen sulphide, calibrated as the manufacturer specifies and bump-tested before each use.
- Test from outside the space, using a pump and probe, at the top, middle and bottom, because light gases (methane) collect high and heavy gases (H2S, CO2, solvent vapours) collect low. Allow the instrument response time for the length of the sampling hose.
- Keep testing while people are inside: entrants or the attendant should carry a continuous personal monitor.
6. Ventilation
Mechanical ventilation is the usual way of meeting GSR 5(2)(a). Place the fan intake in clean air, well away from engine exhausts, run the ducting to the bottom of the space so fresh air sweeps the floor, and keep ventilation running throughout the work. Size the airflow for the space and the contaminants; the design is a judgement for the competent person.
7. The Attendant and Rescue
GSR 5(3)(c) requires, for breathing-apparatus entries, at least one person trained in resuscitation to remain immediately outside the entrance; good practice applies an attendant to every entry. The attendant:
- stays at the entrance and keeps continuous contact with the entrants;
- keeps the entry log and watches ventilation and conditions outside;
- raises the alarm and starts non-entry rescue (winching out an entrant on a lifeline from a tripod or davit) if anything goes wrong; and
- does not enter to attempt a rescue unless trained, equipped with breathing apparatus and backed up. Investigators repeatedly find that untrained rescuers make up a large share of confined-space deaths (NIOSH has reported about 60% in its data).
A workable rescue plan includes a rigged tripod or davit and retrieval winch for vertical entries, harnesses and lifelines on entrants, escape breathing apparatus where atmospheres could change suddenly, and a trained, equipped rescue team where non-entry retrieval is impossible. Public emergency services may take too long to be the primary plan.
8. Summary Matrix
| Requirement | GSR 5 reference |
|---|---|
| Air tested and certified safe in writing by a competent person | 5(1) |
| Below 20% oxygen or hazardous gas likely: purge and ventilate, and isolate by blanking or locked valves | 5(2) |
| Otherwise: approved breathing apparatus, harness and rope, attendant trained in resuscitation, resuscitation equipment | 5(3) |
| Everyone out when work is complete | 5(4) |
| Flammables: no more than 25% LEL (no ignition) or 10% LEL (other work) | 5(5) |
| Same rules for work immediately outside the space | 5(6) |
| Excavations and silos | CR 13(2)(j); CR 20(7) |
9. The CHSM's Oversight
The Construction Health and Safety Manager audits permits and test records, checks detector bump tests and calibration, confirms isolation by blanking or locked valves, verifies that attendants and rescue equipment are in place before entry, and runs rescue drills so that the plan works in practice.
A civil engineering contractor is tasked with installing ductile iron pipework inside a 5-metre-deep stormwater junction chamber that has remained sealed for six months. Before allowing the piping crew to descend the access ladder, the site foreman lowers the sensor probe of a calibrated multi-gas monitor 300 mm below the top chamber opening. The monitor reads: O2: 20.8%, Combustible Gas: 0% LEL, CO: 2 ppm, H2S: 0 ppm. The foreman signs the Confined Space Entry Permit and authorizes immediate entry. Why is this atmospheric testing protocol legally and technically invalid under General Safety Regulation 5?
The protocol is invalid because multi-gas detectors are prohibited on construction sites; only chemical detection indicator tubes certified by SABS may be utilized.
The protocol is invalid because atmospheric testing is only legally required if the chamber depth exceeds 10 metres or if sewage sludge is visibly present.
Invalid: the air must be tested at the top, middle and bottom, because heavier-than-air gases such as hydrogen sulphide collect low.
The protocol is invalid because testing must be performed exclusively while wearing a positive-pressure Self-Contained Breathing Apparatus (SCBA) inside the space.
During maintenance work inside an underground concrete pump sump, two mechanical fitters are exposed to an unanticipated surge of toxic sewer gases and lose consciousness. The appointed Standby Person (sentry) stationed immediately outside the access manhole observes the fallen workers. Under General Safety Regulation 5 and mandatory confined space emergency procedures, what is the standby person's immediate statutory duty?
The standby person must immediately descend the ladder into the sump to pull the unconscious workers out before brain hypoxia sets in.
The standby person must seal the manhole cover to prevent toxic sewer gases from escaping into the surrounding site atmosphere and wait for the project manager.
The standby person must put on a standard cartridge respirator and climb down with a spare air cylinder to revive the fallen fitters.
Stay outside, raise the alarm and start non-entry retrieval with the tripod winch while the trained rescue team responds.
Prior to authorizing entry into a decommissioned underground fuel storage tank for sandblasting, atmospheric sampling reveals: Oxygen: 19.1%, Combustible Vapors: 14% LEL, Carbon Monoxide: 8 ppm, Hydrogen Sulfide: 1 ppm. The painting contractor proposes introducing pure oxygen from an industrial gas cylinder into the tank manway to raise the oxygen level to 21% before workers enter. How must the registered Construction Health and Safety Manager evaluate this proposal under GSR 5 and OHS Act principles?
Reject it: pure oxygen creates a severe fire and explosion risk, and entry is barred because oxygen is below 20% and vapour exceeds 10% of the LEL.
The proposal is acceptable provided the oxygen cylinder is fitted with a calibrated medical regulator and industrial spark-proof blowers circulate the oxygen.
The proposal is acceptable because pure oxygen enrichment is the fastest method to displace hazardous combustible hydrocarbon vapors.
The proposal complies with General Safety Regulation 5 provided that workers wear anti-static footwear and cotton overalls.
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