Gas Purging & First-Gas Commissioning SWMS
A Safe Work Method Statement for gas purging & first-gas commissioning covering all key hazards, controls and regulatory requirements. This is classified as high-risk construction work under WHS Regulation 2025.
SWMS variants reference your state’s WHS legislation. Instant download after payment.
Gas purging and commissioning covers the purging of gas installations and pipework — removing air when bringing a system into service, or removing gas when taking it out of service — and the commissioning that follows when a system is brought into use. Purging is one of the highest-risk gasfitting operations because it deliberately moves a flammable gas-air interface through the system, and an ignition during purging can cause a flash fire or explosion. The work demands rigorous ignition control, controlled purge points, and atmospheric monitoring. This document is written on the basis that purging and commissioning are carried out by a licensed gasfitter to the gas installation standard, with the purge controlled, ignition sources eliminated, and the system leak tested and commissioned.
Gas purging and commissioning are carried out to AS/NZS 5601.1:2022 Gas installations Part 1, the prevailing standard called up by the state and territory gas safety legislation, which sets the requirements for purging installations and pipework, the leak and pressure testing, and the commissioning. Purging moves a flammable gas-air mixture, so it is carried out to controlled purge points, with ignition sources eliminated and the purge monitored. This document coordinates the gas-standard, purge-control, ignition-control, atmospheric-monitoring and leak-testing controls so the system is purged and commissioned without an ignition incident.
Hazards identified
9 hazards covered, sorted by priority.
Flash fire or explosion from ignition of the flammable mixture being purged
Fire, explosion or asphyxiation from gas released during purging
Asphyxiation or explosion where purged gas accumulates
A flammable gas-air mixture remaining in the system after an incomplete purge
Ignition from a naked flame, electrical switching or static during purging
Uncontrolled gas release during the purge and commissioning
Carbon monoxide poisoning where combustion is not correct on commissioning
Gas released to an unsafe location or accumulating without venting
Gas accumulation and restricted egress where purging in a confined space
Control measures
Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.
- 1Engineering: purge the installation or pipework to AS/NZS 5601.1:2022 — to controlled purge points, venting to a safe location, with the purge volume and method to the standard so a flammable mixture does not remain or accumulate.
- 2Administrative: control all ignition sources during the work — no naked flames, no electrical switching, and control of static — and use a gas detector or approved leak-detection fluid rather than a flame for leak finding.
- 3Administrative: monitor the atmosphere during the purge, confirm the purge is complete, and verify there is no flammable mixture remaining in the system before commissioning.
- 4Engineering: vent the purge to a safe external location away from ignition sources, drains and openings, and not into an enclosed or confined area where gas could accumulate.
- 5Engineering: manage the stored pressure and gas of the system, controlling the release during the purge so gas is not released uncontrolled.
- 6Administrative: leak test and pressure test the installation, and on commissioning carry out combustion testing with a carbon monoxide check on the appliances.
- 7Administrative: where purging in a confined or restricted space, apply the confined space and atmospheric controls, recognising that gas can accumulate in the space.
- 8Administrative: ensure the work is carried out and certified by an appropriately licensed gasfitter or plumber under the relevant state or territory gasfitting and plumbing licensing scheme, with a compliance certificate issued where required.
- 9Administrative: all workers must hold a valid White Card (General Construction Induction Training, CPCCWHS1001) before entering any construction workplace, with the gasfitting, plumbing and any confined space competencies and licences required for the work.
- 10Administrative: conduct a daily pre-start toolbox talk covering the day's work, identified hazards, isolations, required PPE and emergency procedures, and record attendance in the consultation section.
- 11Administrative: consult workers and any health and safety representatives on the work and its risks, record the consultation, and keep this document available at the workplace.
- 12PPE: eye protection to AS/NZS 1337.1, hearing protection where required, gloves appropriate to the task, and Class I or Class II safety footwear with protective toecap to AS/NZS 2210.3.
- 13Administrative: review and update this SWMS whenever the work scope changes, after any incident or near miss, when a worker or health and safety representative raises a concern, when new hazards are identified, or at minimum every 12 months.
Applicable Codes of Practice
The prevailing gas installation standard for purging installations and pipework, leak testing and commissioning.
Atmospheric testing, ventilation, entry permit and rescue controls where the work involves entry into a confined space.
Management of the gas and oxidising gases and the fire and oxygen-enrichment hazards.
The risk management process and hierarchy of controls applied to the hazards of the work.
Selection, fit testing and use of respiratory protection where atmospheric hazards, purging or confined conditions require it.
High-Risk Construction Work triggered
Where purging is carried out in a confined or restricted space in which gas can accumulate, the work is high risk construction work requiring a SWMS before the work commences.
This is licensed gasfitting or plumbing work that, in the circumstances described, is high risk construction work — in or near a confined space — so a SWMS must be prepared before the work commences, kept readily accessible, reviewed as necessary, and given to the principal contractor if one is appointed. The work is carried out to AS/NZS 5601.1:2022 and, where applicable, the LP Gas, medical gas and pipeline standards, which are called up by the state and territory gas safety legislation, with the excavation, confined space, pressurised-gas-main or work-at-height controls applied as relevant. A failure in this work can cause a major gas release, fire, explosion or patient harm, and breaches of the gas legislation and the primary duty of care under the model WHS Act are actively enforced, with offence categories running from failure-to-comply through to reckless conduct, and the most serious breaches carrying imprisonment for individuals. Body-corporate maxima are substantial and indexed; the current maximum follows the prevailing schedule of the responsible regulator.
Who this is for
- →Licensed gasfitters purging and commissioning gas installations.
- →Plumbing and gasfitting businesses carrying out purging and commissioning.
- →Industrial and commercial gas commissioning specialists.
- →PCBUs bringing gas installations into or out of service.
- →PCBU safety managers and supervisors coordinating the purge-control and ignition controls.
What you receive
- ✓Editable Microsoft Word document (.docx) fully compatible with Microsoft Word 2016 and newer, Google Docs, and LibreOffice Writer.
- ✓Title page with editable fields for PCBU name, ABN, site address, project name, principal contractor details, and document revision date.
- ✓Hazard register with the gas purging and commissioning hazards — each with a documented consequence, inherent risk rating on a 5x5 likelihood-consequence matrix, hierarchy-of-control measures, and residual risk rating.
- ✓Gas purging prompts referencing AS/NZS 5601.1:2022, a controlled-purge-point and safe-venting section, an ignition-control and atmospheric-monitoring section, and a leak-test and commissioning record.
- ✓Licensing and compliance-certificate prompts for the relevant gasfitting and plumbing scheme, the Type B or medical gas certification where applicable, and a respiratory protection selection and fit-test record per AS/NZS 1715 where relevant.
- ✓Worker consultation record per the model WHS Act consultation duty and a worker sign-on register (blank, expandable).
- ✓Applicable legislation and Codes of Practice schedule pre-populated for the model WHS jurisdiction with a state-variance reference table covering the harmonised states, plus Victoria.
- ✓Emergency procedure template and a revision log.
Worked example
A licensed gasfitter is engaged to purge and commission a new gas installation being brought into service. The installation is purged to AS/NZS 5601.1:2022, to controlled purge points venting to a safe external location away from ignition sources, drains and openings, with the purge volume and method to the standard so a flammable mixture does not remain or accumulate. All ignition sources are controlled — no naked flames, no electrical switching, static controlled. The atmosphere is monitored during the purge, the purge is confirmed complete, and the absence of a flammable mixture verified before commissioning. The stored pressure and gas of the system are managed so gas is not released uncontrolled. The installation is leak tested and pressure tested, and on commissioning combustion testing with a carbon monoxide check is carried out on the appliances. The work is carried out so gas is not vented into an enclosed area. The gasfitter completes the commissioning, confirms the system is safe, and retains the records.
Related legislation
- Model Work Health and Safety Act — primary duty of care; the duty to consult workers; the reckless-conduct offence; and notifiable-incident provisions, as enacted in each jurisdiction.
- Model Work Health and Safety Regulations — Section 291 high risk construction work and the SWMS preparation and review duties, and the confined space, excavation and pressurised-gas provisions where applicable, as enacted in each jurisdiction.
- The gas installation standard AS/NZS 5601.1:2022, the LP Gas storage standard AS/NZS 1596, the medical gas standard AS 2896, and the relevant plumbing and drainage standards AS/NZS 3500, are called up by the state and territory gas and plumbing safety legislation, together with the Type B and medical gas certification requirements and the gas network operator's requirements where applicable.
- Gasfitting and plumbing work is licensed under each state and territory's gasfitting and plumbing licensing scheme, with Type B authorisation and medical gas certification required for that work, and compliance certification required for notifiable work.
- Victoria operates under the Occupational Health and Safety Act 2004 and the Occupational Health and Safety Regulations 2017, with the high risk construction work, confined space and excavation provisions applying in place of the model instruments.
Frequently asked questions
What is gas purging?
Gas purging is the removal of air from a gas installation when bringing it into service, or the removal of gas when taking it out of service, by displacing the contents to controlled purge points. It deliberately moves a flammable gas-air interface through the system, which is why it is one of the highest-risk gasfitting operations and demands rigorous ignition control.
Why is purging so high-risk?
Purging moves a flammable gas-air mixture through the system, and an ignition during purging can cause a flash fire or explosion. For that reason all ignition sources are controlled, the purge is carried out to controlled purge points venting to a safe location, the atmosphere is monitored, and the purge is confirmed complete with no flammable mixture remaining before commissioning.
Where is the purge vented?
The purge is vented to a safe external location away from ignition sources, drains and openings, and not into an enclosed or confined area where gas could accumulate. Venting the purge to a safe location prevents the purged gas from accumulating and being ignited, which is a key control for the operation.
How is the purge confirmed complete?
The atmosphere is monitored during the purge, and the purge is confirmed complete with no flammable gas-air mixture remaining in the system before the installation is commissioned. Confirming the purge is complete ensures a flammable mixture does not remain in the system, which is essential before the system is brought into use.
Is the system commissioned after purging?
Yes. After purging, the installation is leak tested and pressure tested, and on commissioning combustion testing with a carbon monoxide check is carried out on the appliances. The commissioning confirms the system is gas-tight and the appliances burn correctly, completing the safe bringing of the system into service.