Gas Decommissioning & Make-Safe SWMS
A Safe Work Method Statement for gas decommissioning & make-safe 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 decommissioning and capping covers the safe removal of gas installations and pipework from service — isolating the supply, purging the gas from the system, disconnecting appliances and pipework, and capping the gas supply so it is left permanently safe. It is high-consequence gasfitting because it involves working on a system that contains or has contained flammable gas, and an incomplete isolation, an inadequate purge or an unsealed cap can leave a gas hazard. This document is written on the basis that gas decommissioning and capping are carried out by a licensed gasfitter to the gas installation standard, with the supply isolated, the gas purged, and the supply capped and confirmed gas-tight.
Gas decommissioning and capping 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 isolating, purging, disconnecting and capping gas installations. The work involves purging the flammable gas from the system, with the ignition control that purging demands, and capping the supply so it is permanently safe. This document coordinates the gas-standard, isolation, purge, ignition-control and capping controls so the installation is decommissioned and left safe.
Hazards identified
9 hazards covered, sorted by priority.
Fire, explosion or asphyxiation from gas released or remaining during the work
Flash fire or explosion from an ignition source during the work
A live gas supply remaining where the isolation is incomplete
A flammable gas-air mixture remaining in the system after an incomplete purge
Gas leak from a supply not capped gas-tight and left permanently safe
Asphyxiation or explosion where purged or released gas accumulates
Uncontrolled gas release during isolation, purge and disconnection
Gas accumulation and restricted egress where working in a confined space
Musculoskeletal injury removing appliances and pipework
Control measures
Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.
- 1Administrative: isolate the gas supply and confirm the isolation before the work, and decommission and cap the installation to AS/NZS 5601.1:2022.
- 2Engineering: purge the gas from the system to controlled purge points venting to a safe location, confirming the purge is complete and no flammable mixture remains, with the purge to the standard.
- 3Administrative: 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.
- 4Engineering: cap the gas supply so it is sealed gas-tight and left permanently safe, and leak test the cap to confirm it is gas-tight.
- 5Administrative: monitor the atmosphere during purging and disconnection, ventilate the area, and not vent gas into an enclosed area where it could accumulate.
- 6Engineering: manage the stored pressure and gas of the system, controlling the release during isolation, purge and disconnection so gas is not released uncontrolled.
- 7Administrative: where the work is in a confined or restricted space, apply the confined space and atmospheric controls, and use correct technique to remove appliances and pipework.
- 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 isolating, purging, disconnecting and capping gas installations.
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 gas decommissioning and capping are 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 decommissioning and capping gas installations.
- →Plumbing and gasfitting businesses carrying out gas removal and capping.
- →Demolition and strip-out gasfitters making installations permanently safe.
- →Property owners and PCBUs decommissioning gas installations.
- →PCBU safety managers and supervisors coordinating the isolation, purge and capping 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 decommissioning and capping hazards — each with a documented consequence, inherent risk rating on a 5x5 likelihood-consequence matrix, hierarchy-of-control measures, and residual risk rating.
- ✓Gas decommissioning prompts referencing AS/NZS 5601.1:2022, an isolation and purge section, an ignition-control and atmospheric-monitoring section, and a capping and leak-test 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 decommission and cap the gas installation in a building being refurbished. The gas supply is isolated and the isolation confirmed before the work, and the installation is decommissioned and capped to AS/NZS 5601.1:2022. The gas is purged from the system to controlled purge points venting to a safe location, with the purge confirmed complete and no flammable mixture remaining. All ignition sources are controlled during purging and disconnection, and the atmosphere is monitored and the area ventilated, with gas not vented into an enclosed area. The stored pressure and gas of the system are managed so gas is not released uncontrolled. The appliances and pipework are disconnected and removed, and the gas supply is capped so it is sealed gas-tight and left permanently safe, with the cap leak tested to confirm it is gas-tight. The gasfitter confirms the installation is decommissioned and safe, issues the documentation, 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 does gas decommissioning and capping involve?
Gas decommissioning and capping is the safe removal of a gas installation from service — isolating the supply, purging the gas from the system, disconnecting appliances and pipework, and capping the supply so it is left permanently safe. It is carried out to AS/NZS 5601.1:2022, with the cap leak tested to confirm the supply is gas-tight.
Why is decommissioning a gas installation high-consequence?
Decommissioning involves working on a system that contains or has contained flammable gas, and an incomplete isolation, an inadequate purge or an unsealed cap can leave a gas hazard. For that reason the supply is isolated and confirmed, the gas is purged with rigorous ignition control, and the supply is capped gas-tight and leak tested before the work is complete.
How is the gas supply made permanently safe?
The gas supply is capped so it is sealed gas-tight and left permanently safe, and the cap is leak tested to confirm it is gas-tight. Capping the supply correctly ensures no gas can escape from the decommissioned installation, leaving it permanently safe after the appliances and pipework have been disconnected and removed.
Is the gas purged during decommissioning?
Yes. The gas is purged from the system to controlled purge points venting to a safe location, with the purge confirmed complete and no flammable mixture remaining, and rigorous ignition control throughout. Purging removes the flammable gas from the system before it is disconnected and capped, which is an essential part of decommissioning safely.
Who can decommission and cap a gas installation?
Gas decommissioning and capping is licensed gasfitting work carried out by a licensed gasfitter to AS/NZS 5601.1:2022. Because it involves working on a system containing flammable gas and leaving the supply permanently safe, it is reserved to a licensed practitioner, and the cap is leak tested to confirm the supply is gas-tight.