Diesel Fuel System Installation & Polishing SWMS
SWMS variants reference your state’s WHS legislation. Instant download after payment.
Diesel fuel system installation and fuel polishing is high risk construction work in New South Wales under the contaminated or flammable atmosphere category, the confined space category, the fuel line category, the excavation category for underground tanks, and the powered mobile plant category. Section 291 of the Work Health and Safety Regulation 2025 (NSW) captures it and a safe work method statement is required under section 299. SafeWork NSW is the regulator. AS 1940 is the primary standard for the work and AS 2865 governs tank entry.
Diesel is classified as combustible rather than flammable, and that classification gets people hurt. The flash point above about 61.5°C is true of the bulk liquid at ambient — but it is not true of a vapour space in a warm tank, it is not true of diesel mist or spray from a pressurised line, which ignites readily at ambient, and it is emphatically not true of an 'empty' tank. A tank that has been drained is the most dangerous state it will ever be in: the liquid is gone and the vapour space sits in the flammable range with nothing to displace it.
Polishing exists because diesel goes bad, and what makes it go bad is what makes the job high risk. Water settles under stored fuel, and the fuel-water interface grows a microbial colony — the 'diesel bug'. Among that colony are sulfate-reducing bacteria, which generate hydrogen sulphide. Opening or entering a microbially contaminated tank can release H2S at concentrations that are immediately dangerous, from a tank nobody would think to test for it because it is 'just diesel'. The sludge at the bottom of a neglected fuel tank is not sediment — it is a biological reactor.
Hazards identified
14 hazards covered, sorted by priority.
Fatality — H2S from the microbial colony drops the entrant, and drops the rescuer next
Fire or explosion — an 'empty' tank's vapour space sits in the flammable range
Fatality — vapour, H2S and oxygen deficiency in one enclosed vessel
Fatality — fire or explosion ignited by static generated by the fuel's own flow
Serious injury — high-pressure injection requiring urgent surgical intervention
Fatality — crush injury from the tank or pumpset during delivery and placement
Fatality — burial in the excavation, or a strike on an unplotted forecourt fuel line
Environmental prosecution and contamination — a discharge to land, stormwater or sewer
Fire or explosion — an electrical spark in a fuel vapour zone
Skin irritation and suspected carcinogenic exposure on repeated contact
Serious injury — a cap or plug released as a projectile during pressure test
Slips and falls on fuel-contaminated surfaces, which hold it in a bund
Permanent noise-induced hearing loss from pump and generator operation
Musculoskeletal injury from handling pumps, filter housings and pipe spools
Control measures
Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.
- 1Polish, dewater and clean through closed equipment and a licensed contractor from outside the tank — the sludge in a neglected fuel tank is a biological reactor, not sediment.
- 2Test the atmosphere for H2S as well as oxygen and LEL before any opening and continuously during work — a crew testing a diesel tank for flammables alone will not see the thing that drops them.
- 3Treat the tank as H2S-credible whenever water, sludge or microbial growth is present or its history is unknown, and work upwind of any opening.
- 4Recognise that H2S deadens the sense of smell at roughly 100–150 ppm — the smell going away means it is getting worse, and odour is never a control.
- 5Prohibit all cutting, welding, grinding and drilling on or within the assessed zone of a tank that has contained fuel until it is cleaned, gas freed and certified by a competent person.
- 6Require a confined space entry permit under AS 2865 with a standby person who does not enter, rescue in place before entry, and the polishing and transfer pumps locked out.
- 7Bond and earth the tank, the tanker, the pump and the receiving vessel before any transfer and keep them bonded until it is complete — flowing fuel generates static and splash filling generates far more.
- 8Use bottom or submerged filling rather than splash filling, limit flow at the start of a fill, and prohibit sampling or dipping during or immediately after a fill because the charge takes time to relax.
- 9Depressurise and isolate before any line, fitting or filter is touched, and locate leaks with cardboard rather than a hand — diesel mist from a pinhole ignites readily even though the bulk liquid will not.
- 10Select and install electrical equipment for the hazardous zone classification under AS 1940 and the AS/NZS 60079 series, with no non-rated tool, torch, phone or camera in the classified zone.
- 11Bench, batter or shore the excavation to a competent person's design, prove every service by non-destructive means, and have the owner isolate the existing fuel system before any dig near it.
- 12Bund the tank and transfer point, protect stormwater inlets before work begins, and attend the transfer at all times — a discharge to land, stormwater or sewer is an offence under the POEO Act 1997 (NSW).
- 13Test hydrostatically rather than pneumatically wherever the standard and the designer permit, with the area cleared and nobody in line with a cap, blank or flange.
- 14Use closed transfer and drain-down before any break rather than catching fuel by hand, and remove contaminated clothing immediately rather than at the end of the shift.
Applicable Codes of Practice
The benchmark for entry permits, atmospheric testing, ventilation, standby and non-entry rescue — a fuel tank is a confined space and the atmospheric test must include H2S.
The benchmark for diesel and its vapour as hazardous chemicals, including the workplace exposure standard and the control of ignition.
The benchmark for ground stability and the location and protection of underground essential services — critical in a forecourt where fuel lines are not reliably plotted.
The primary standard for this work: tank installation, bunding, separation distances, ventilation, ignition source control, hot work on tanks that have contained fuel, and the treatment of vapour spaces.
Confined space classification, atmospheric testing, entry permits, standby arrangements and non-entry rescue.
The installation, connection, support and testing requirements for the fuel pipework, including the test regime and relief settings.
High-Risk Construction Work triggered
A fuel tank is a confined space with restricted egress containing fuel vapour, H2S from microbial contamination and an oxygen-deficient atmosphere. Entry is required for cleaning, inspection and internal work during both installation and polishing.
Underground tanks and fuel lines routinely require excavation deeper than 1.5 metres, in forecourts where existing fuel lines and vapour recovery are not reliably plotted.
The work is on fuel lines throughout — installing them, pressure testing them, and breaking into them for filter changes and polishing connections.
The polishing pump, transfer pump, gauging and lighting are energised within or adjacent to a fuel vapour zone, where an electrical spark is an ignition source.
Fuel vapour sits in the flammable range in the vapour space of any tank that has held diesel, and the microbial colony at the fuel-water interface generates hydrogen sulphide.
Tanks, pumpsets and delivery vehicles are placed and moved by crane, truck and excavator around the tank compound and the excavation.
Carrying out high risk construction work without a compliant SWMS is an offence under the Work Health and Safety Regulation 2025 (NSW). An H2S fatality in a fuel tank attracts immediate SafeWork NSW attention and is almost always a multiple-fatality investigation because the mechanism takes the rescuer. Separately, a fuel discharge to land, stormwater or sewer is an offence under the POEO Act 1997 (NSW), is reportable, and carries its own substantial penalties.
Who this is for
- →Plumbing and fuel system contractors installing bulk and day tanks, fuel lines and transfer systems
- →Fuel polishing and tank cleaning contractors servicing standby generator and fire pump installations
- →Standby power contractors installing diesel fuel systems for generators and fire pumpsets
- →Service station and bulk fuel infrastructure contractors
- →Principal contractors and facility managers required to obtain and review a SWMS before fuel works start
What you receive
- ✓A complete, editable Safe Work Method Statement authored for New South Wales — the WHS Act 2011 (NSW), the WHS Regulation 2025 (NSW), and SafeWork NSW as regulator, with correct section numbers throughout
- ✓14 identified hazards with initial and residual risk ratings on a 5x5 matrix, each with the full hierarchy of control from elimination through to PPE
- ✓The diesel bug control set — H2S from sulfate-reducing bacteria at the fuel-water interface, and the requirement that tank testing includes H2S and not just O2 and LEL
- ✓The vapour space control set built on the fact that an empty tank is the most dangerous state it will ever be in
- ✓The static control set — bonding and earthing before transfer, bottom filling rather than splash filling, and no sampling until the charge has relaxed
- ✓The hazardous zone control set under AS 1940 and the AS/NZS 60079 series, with no non-rated tool, torch or phone in the classified zone
- ✓The full high risk construction work breakdown — contaminated atmosphere, confined space, fuel lines, excavation, energised electrical and mobile plant — with the reason each category applies
- ✓A PPE matrix mapping each task to the required equipment and Australian Standard, including multi-gas monitoring that includes H2S and anti-static clothing in the vapour zone
- ✓Microsoft Word (.docx) format, unbranded, editable fields for PCBU, ABN, site, dates and worker sign-on
Worked example
A contractor is polishing the fuel in a standby generator tank at a data centre. The fuel has been in the tank four years and the last sample showed water. The crew opens the inspection hatch to drop the suction line in. The tank is above ground, in a plant room, and nobody considers it a confined space because nobody is going inside it. The technician leans over the open hatch to position the line. The sludge is disturbed as the suction starts. Hydrogen sulphide comes off the water layer. He is over the opening when it does, takes a breath at concentration, and goes down across the hatch. The controls in this SWMS break that chain before the hatch is opened. Atmospheric testing includes H2S, not just oxygen and LEL — because a crew testing a diesel tank thinks about fire, and H2S is what kills them. The tank is treated as H2S-credible whenever water, sludge or microbial growth is present or its history is unknown, which four-year-old fuel with a water cut plainly satisfies. Work is carried out upwind of any opening rather than over it. And the document states that odour is never a control, because H2S deadens the sense of smell at roughly 100–150 ppm — precisely the concentration at which it becomes lethal, so the warning vanishes exactly when it matters.
Related legislation
- Work Health and Safety Act 2011 (NSW) — Section 19 primary duty of care; Section 47 consultation; Sections 35–38 notifiable incidents
- Work Health and Safety Regulation 2025 (NSW) — Section 291 high risk construction work; Section 299 SWMS required and content prescribed; Section 302 review
- Work Health and Safety Regulation 2025 (NSW) — Part 4.3 Division 2: confined spaces, and Division 3: excavation for underground tanks and lines
- Protection of the Environment Operations Act 1997 (NSW) — a fuel spill or discharge of contaminated water to land, stormwater or sewer is an offence and is reportable; polishing waste and tank sludge are tracked and disposed of through a licensed contractor
- Work Health and Safety Regulation 2025 (NSW) — Chapter 7: hazardous chemicals, including the workplace exposure standards for diesel vapour and hydrogen sulphide
Frequently asked questions
Diesel is combustible, not flammable. Why is this treated as a fire risk?
Because the classification describes the bulk liquid at ambient, and almost nothing on this job is the bulk liquid at ambient. A vapour space in a warm tank sits in the flammable range. Diesel mist from a pressurised line ignites readily at ambient temperature. And a drained tank is the most dangerous state it will ever be in — the liquid is gone and the vapour space has nothing to displace it. 'An empty diesel tank is more dangerous than a full one' is a literal statement, not a figure of speech.
What is the diesel bug and why does it matter to safety?
Water settles under stored fuel and the fuel-water interface grows a microbial colony. Among that colony are sulfate-reducing bacteria, which generate hydrogen sulphide. That is why polishing exists — but it also means opening or entering a contaminated tank can release H2S at immediately dangerous concentrations, from a tank nobody would think to test for it because it is 'just diesel'. The sludge at the bottom is a biological reactor, not sediment.
We test for oxygen and LEL. Is that enough for a fuel tank?
No, and this is the specific gap the SWMS closes. A crew approaching a fuel tank thinks about fire, so they test for flammables and oxygen. H2S is generated biologically, is not what anyone expects from diesel, and deadens the sense of smell at roughly 100–150 ppm. Testing that omits H2S will not see the thing that drops the entrant.
Do we need this if the tank is above ground in a plant room?
Yes. A tank is a confined space regardless of whether it sits above or below grade — restricted egress, an atmosphere that can be contaminated or oxygen-deficient, and not intended for continuous occupancy. The dangerous moment is frequently at the open hatch rather than inside, with a worker leaning over an opening as disturbed sludge releases H2S. The SWMS requires work upwind of the opening for exactly that reason.