- Author
- Byron Raal, CAS Founder-Editor About the author
- Checked against
- AS/NZS 3788AS 4343
- Date last checked
- 17 August 2026
Every air receiver in an Australian workplace is pressure equipment, and work health and safety laws require it to be inspected for as long as it’s in service: model WHS regulation 224 calls for inspection on a regular basis by a competent person, and Victoria’s OHS Regulations 2017 require plant to be inspected to the extent necessary to monitor the risk. AS/NZS 3788:2024 Amd 1:2025 is the current edition of the technical standard used to decide what regular means, though your own regulator may still work to an earlier edition: SafeWork SA and WorkSafe Victoria both currently point duty holders at AS/NZS 3788:2006. The interval is set by the receiver’s pressure-volume product (pV, in MPa·L), not by its hazard level. Under Table 4.1 Item 6, receivers above pV 150 MPa·L require external inspection every 2 years and internal inspection every 4 years, with a 12-year extended interval available under the standard’s conditions. At or below 150 MPa·L, the external, internal and extended intervals are set under Table 4.1 Note 6 at the competent person’s discretion. The duty names a competent person; it doesn’t require that person to be independent of you, though your insurer or your customer might. Common plant-room sizes can land in the top band: a 200 L receiver at 800 kPa computes to 160 MPa·L, so work out each vessel’s pV from its own design pressure and volume rather than guessing from its size.
Two numbers, two duties
pV sets the inspection interval, H sets registration
The same 500 L receiver at 800 kPa (0.8 MPa), worked both ways.
Inspection cadenceAS/NZS 3788:2024 Amd 1:2025, Table 4.1 Item 6
- pV = 0.8 MPa × 500 L = 400 MPa·L
Above 150 MPa·L - External inspection
- 2-yearly
- Internal inspection
- 4-yearly
- Extended interval
- 12 years, conditional
- 12-year extended interval available under the standard’s conditions. At or below 150 MPa·L: intervals are set under Table 4.1 Note 6 at the competent person’s discretion.
RegistrationAS 4343:2014 hazard level, H = 10 × P × V for clean air
- H = 10 × 0.8 × 500 = 4,000
Hazard Level C - Design registration
- levels A, B, C or D
- Item registration
- levels A, B or C
- Serially produced vessels
- outside item registration
- Model WHS Schedule 5. Hazard level is the input to the registration question, not the answer to it: work the call through your own state’s rules.
For clean compressed air the two numbers differ by exactly the gas factor of 10, which is why they get muddled.
Source: AS/NZS 3788:2024 Amd 1:2025 Table 4.1 Item 6 and AS 4343:2014.
Key takeaways
- In-service inspection of an air receiver is a recurring duty under your state’s work health and safety laws: model WHS regulation 224 calls for inspection on a regular basis by a competent person, and Victoria requires plant to be inspected to the extent necessary to monitor the risk. Whether AS/NZS 3788 carries legal force on top of that depends on your state and on the scheme, so check your own regulator’s current material.
- The interval turns on the pV product (design pressure in MPa times volume in litres), not the AS 4343 hazard level. Registration and inspection run on different numbers.
- Above pV 150 MPa·L: external inspection 2-yearly, internal inspection 4-yearly, with a 12-year extended interval available under the standard’s conditions (Table 4.1 Item 6).
- At or below 150 MPa·L the intervals are set under Table 4.1 Note 6 at the competent person’s discretion. That’s not an exemption, and it’s not a hidden 4-yearly rule either.
- The legal duty names a competent person, and the instruments we’ve read don’t make independence part of it. SafeWork SA names Engineers Australia, the Australasian Institute of Engineer Surveyors and AICIP as examples of bodies whose recognition it will accept. If there’s no report on file, you may not be able to demonstrate to a regulator, an insurer or a buyer that the inspection happened.
The duty: who owes it and where it comes from
If your site runs an air receiver, someone on your site owes this duty. In most states and territories the model WHS Regulations apply. Regulation 224 says the person with management or control of pressure equipment must ensure it’s inspected on a regular basis by a competent person. It doesn’t name AS/NZS 3788 and it doesn’t set an interval. Victoria isn’t a model WHS state and words its duty differently: OHS Regulations 2017 regulation 105 requires plant to be inspected to the extent necessary to ensure the risk from using it is monitored, and WorkSafe Victoria then publishes competent-person intervals in guidance. Similar result in practice, different words in the instrument.
Whether AS/NZS 3788 itself carries legal force depends on the state and on the scheme, so work it that way instead of looking for a national answer. In the model WHS registration scheme it’s AS 4343:2014, not AS/NZS 3788, that the regulations name: Schedule 5 uses AS 4343 hazard levels to decide what needs design and item registration. South Australia goes further on inspection, with SafeWork SA telling duty holders the inspection must be in accordance with AS/NZS 3788:2006 and that the certificate must say so. Queensland runs the ordinary regulation 224 duty, but a separate scheme, the Petroleum and Gas (Safety) Regulation 2018, lists AS/NZS 3788 as a mandatory standard for inspecting fuel gas tanks; that’s a different scheme, not the ordinary air receiver path. Victoria’s OHS Regulations name AS 4343 for records but don’t prescribe an inspection standard. Check your own regulator’s current page before you rely on any of it.
Here’s the part that catches people: the duty recurs for the life of the vessel. It’s common enough to find a receiver that was registered once, had its paperwork filed, and has run for years since with no inspection records at all. If you can’t put your hand on the last inspection report right now, this page is for you.
Sizing, selection and registration are covered in depth in our air receiver tanks guide; this page covers the recurring inspection duty that starts once the vessel is in service.
Need the registration side checked too? Get the worksheet.
Free two-page PDF. Inspection cadence comes from the pV product, and registration comes from the AS 4343 hazard level, so the two need separate answers. The worksheet runs the hazard level calculation in five lines and pairs the answer with the registration checklist for your state or territory. Email only, and the download is on the next screen.
We email you the PDF and nothing else unless you ask. Form not loading? Email byron@compressedairsolutions.com.au with your enquiry.
The three pV bands under Table 4.1 Item 6
AS/NZS 3788:2024 Amd 1:2025 gives compressed air containing vessels their own row in Table 4.1 (Item 6), separate from the generic process-vessel cadences in the same table. The interval comes from the pV product: design pressure in MPa multiplied by volume in litres, giving a figure in MPa·L. A 500 L receiver at 800 kPa (0.8 MPa) has a pV of 400 MPa·L. That’s the whole calculation.
Table 4.1 Item 6 then sets the cadence in three bands:
| pV product | Commissioning | First in-service | External | Internal | Extended |
|---|---|---|---|---|---|
| Below 100 MPa·L | Not required | Not required | Note 6 | Note 6 | Note 6 |
| Between 100 and 150 MPa·L | Required | Not required | Note 6 | Note 6 | Note 6 |
| Above 150 MPa·L | Required | Not required | 2-yearly | 4-yearly | 12 years |
Source: AS/NZS 3788:2024 Amd 1:2025, Table 4.1 Item 6 (compressed air containing vessels).
Three things worth spelling out.
Common plant-room sizes can land in the top band. A 1,000 L receiver at 1,000 kPa gives pV = 1,000 MPa·L, comfortably above the 150 MPa·L threshold. A 200 L receiver at 800 kPa gives pV = 160 MPa·L, also above. Calculate each vessel from its own design pressure and volume rather than assuming its band from its size. Where a receiver does land above 150, the standard’s cadence is a 2-yearly external and a 4-yearly internal inspection.
Note 6 is discretion, not exemption. At or below 150 MPa·L, the external, internal and extended intervals are set under Table 4.1 Note 6 at the competent person’s discretion. Note 6 is phrased in “should”, not “shall”, and it doesn’t fix intervals. You’ll hear both over-readings in the field: “small receivers are exempt” and “small receivers still owe the 4-yearly internal”. Both are wrong. The standard hands the interval to the competent person for that vessel. What Note 6 doesn’t do is make the question go away.
Don’t self-classify off a boundary figure. If your pV lands near a band boundary, don’t call the band yourself from a brochure figure or a rounded nameplate reading. As printed, the first two rows of Item 6 overlap at exactly 100 MPa·L, so the 2024 table claims that value twice. We’ve settled it one way and used the same answer everywhere on this page: commissioning is required at 100 MPa·L and above. That’s the conservative reading, and it’s what our table and our FAQ both use. Have the competent person make the call on the vessel’s actual design pressure and volume.
One more column worth noticing: first in-service inspection is not required in any band under Item 6. The recurring external and internal cadence is where the duty lives.
External vs internal: what each inspection actually involves
External inspection
The vessel stays in service. A competent person examines the shell, heads, welds, supports and attachments for corrosion, dents, leaks and distortion, checks the condition of the safety devices (relief valve, pressure gauge, isolation and drain valves), and reviews the vessel’s records against what they’re seeing. On an air receiver the drain gets particular attention, because a failed or bypassed drain is how condensate ends up sitting against the bottom of the shell. The output is a documented report with findings and required actions, which goes in your equipment file. Routine duty-holder checks between inspections are covered in the air receiver tanks guide and the compressor maintenance guide; they support the formal inspection, they don’t replace it.
Internal inspection
The vessel comes out of service. It’s depressurised, isolated, drained and opened at its inspection openings so the competent person can examine the internal surfaces directly. On a compressed air receiver the usual story is corrosion: pitting at the bottom of the shell where condensate pools, attack along the waterline, and the condition of internal weld seams, with thickness testing where the surface condition warrants it. Dry, well-drained air carries lower internal-corrosion risk than many process fluids, but internal inspection is not waived outright for larger receivers; that’s precisely what the 4-yearly interval above 150 MPa·L exists to confirm rather than assume.
An internal is a planned outage, which is exactly why sites drift: nobody wants to take the air off a production plant, so the interval slips a year, then five. Book it against a scheduled shutdown and the problem disappears.
Who may do them
The legal duty names a competent person. Model WHS regulation 224 says that and no more: it doesn’t require the inspector to be independent of you. SafeWork SA puts the practical test well, telling duty holders to ask for evidence of qualifications and training in pressure equipment inspection, and naming Engineers Australia, the Australasian Institute of Engineer Surveyors and the Australian Institute for the Certification of Inspection Personnel as examples of bodies that recognise them. So AICIP is one recognised pathway, not the only one. Independence is a separate question, and your insurer or your customer may want it even where the regulation doesn’t, so ask them. This is a formal inspection producing a documented report, not routine servicing, so a compressor technician who doesn’t hold that competency isn’t the person to sign it, however good they are with the machine. Verify credentials against your own state regulator’s requirements before engaging.
H decides registration, pV decides inspection
These two numbers get conflated constantly, so here’s the split.
Hazard level (H) decides registration. Under AS 4343:2014, H = P × V × Fc × Ff × Fs, which for clean compressed air simplifies to H = 10 × P × V. The hazard level determines whether the vessel needs design and plant registration with your state regulator. Run yours through the hazard level calculator, and see the pressure vessel registration guide for the state-by-state picture.
The pV product decides inspection cadence. AS/NZS 3788:2024 Amd 1:2025 Table 4.1 Item 6 bands compressed air containing vessels by the bare pV product, without the factors.
For clean compressed air the two numbers differ by exactly the gas factor of 10, which is why they get muddled. That 500 L receiver at 800 kPa: pV = 400 MPa·L, so it’s in the above-150 inspection band; H = 4,000, which is Hazard Level C. Hazard level is the input to the registration question, not the answer to it. Under model WHS Schedule 5, design registration covers pressure equipment at hazard level A, B, C or D, and item registration covers pressure vessels at A, B or C but expressly excludes gas cylinders, automotive LP Gas fuel vessels and serially produced vessels, so a serially produced receiver can be Hazard Level C and still sit outside item registration. Victoria is different again: its OHS Regulations register plant designs, and the only items of plant they register are amusement structures. Work the registration call through your own state’s rules on the actual vessel. Same vessel, two numbers, two duties. Advice that runs the inspection interval off the hazard level, or the registration call off the bare pV, has mixed up its standards.
The regulator layer, and the Victorian table
The work health and safety law in your state is where the duty comes from, and regulators publish their own guidance on top of it. Read that guidance, and read the edition line in it. AS/NZS 3788:2024 Amd 1:2025 is the current edition of the standard, but WorkSafe Victoria and SafeWork SA both currently point duty holders at AS/NZS 3788:2006. The current edition and the edition your regulator cites are two different things.
WorkSafe Victoria’s published air receiver guidance table draws a single line at 100 MPa·L and cites the 2006 edition of AS/NZS 3788. The current 2024 edition differs in the band between 100 and 150 MPa·L, where the external and internal intervals sit under Note 6 rather than being fixed at 2 and 4 years, and it adds the 12-year extended interval above 150 MPa·L. Neither document is wrong: one is regulator-published guidance citing the edition current when it was written, the other is the current standard. In Victoria the conservative path is to follow the regulator’s published intervals, a 2-yearly external and a 4-yearly internal above 100 MPa·L. A competent person who recommends different intervals under the current standard should document the basis against the WorkSafe guidance. Above 150 MPa·L the question doesn’t arise; the WorkSafe guidance and the current standard land on the same 2-yearly external and 4-yearly internal cadence.
Records are a per-state question too. Victoria’s OHS Regulations 2017 regulation 106 expressly requires an employer to keep records of inspection and maintenance for pressure vessels at AS 4343 hazard level A, B or C, for as long as they have management or control of the vessel. Under the model WHS Regulations the specific record duty in regulation 237 applies to plant that has to be registered under Part 5.3: keep the records while the plant is in use, and hand them over when you relinquish control of it. Beyond that, a register of pressure equipment, scheduled and recorded inspections and reports signed by the competent person is what an audit or an incident investigation asks for first.
What skipping it actually costs
Nobody budgets for the inspection they’re not doing, so here’s the other side of that ledger.
The incident itself. A receiver can release its stored energy all at once if the shell lets go, and receivers live in plant rooms where people work. Internal corrosion is invisible from the outside; the failure mode the 4-yearly internal is looking for is exactly the one you can’t see on a walkaround.
The investigation after it. An investigation into a pressure equipment incident usually starts with the equipment file. A vessel with no inspection history makes it hard to show you met the duty, and WHS penalties attach to the failure of the duty, not just the outcome. It doesn’t turn a mechanical event into a proven breach by itself; that still depends on which duty applied and what actually happened.
Insurance. An insurer handling a property or injury claim involving an uninspected pressure vessel is likely to ask for the inspection records. What each policy actually requires varies, so read yours; an undocumented inspection regime is simply harder to argue for.
Audits and notices. Regulator visits and customer audits ask for the pressure equipment register. An improvement notice on an overdue vessel is cheap compared to a prohibition notice that takes your air offline until the inspection is done.
Against all of that, an external is a scheduled visit and, for receivers above 150 MPa·L, an internal is a planned outage every four years. It’s one of the cheaper compliance items on your site to be square with.
Find out where your receivers stand, free
If you don’t know your receiver’s pV band, or its last inspection date, or whether the person who last looked at it was actually a competent person, that’s a ten-minute question for the right specialist.
Send three things and I’ll have an independent pressure-equipment specialist verify where your receivers stand against the current standard and your own regulator’s guidance:
- your site postcode
- your state or territory
- what you need proved (overdue for inspection? never inspected? buying, selling or relocating a vessel?)
That is enough for an initial enquiry. Include your location and what you need to resolve; equipment records and operating details may be needed for a specialist assessment. CAS does not sell equipment or carry out inspections. We can review your brief and discuss a suitable Australian provider if one is available. We ask for your written permission before an introduction and explain any referral payment arrangement. There is no cost to enquire.
Form not loading? Email us directly at byron@compressedairsolutions.com.au with your enquiry.
Frequently asked questions
How do I work out the pV product for my air receiver?
Multiply the design pressure in MPa by the volume in litres. Design pressure is on the vessel’s nameplate; 1,000 kPa is 1 MPa. A 500 L receiver with a design pressure of 800 kPa gives pV = 0.8 x 500 = 400 MPa·L. Use design pressure, not your operating setpoint, and note the pV product is not the AS 4343 hazard level, which multiplies in additional factors and governs registration instead. If the nameplate is corroded or missing, have a competent person establish the design data before anything else.
Does a new air receiver need an inspection before it goes into service?
It depends on the pV product. Under AS/NZS 3788:2024 Amd 1:2025 Table 4.1 Item 6, a commissioning inspection is required for compressed air containing vessels at 100 MPa·L and above, and no first in-service inspection is required in any band. Registration is a separate question decided by the AS 4343 hazard level, and for most plant-room receivers it needs sorting before the vessel is used; from there the recurring cadence applies according to the vessel’s pV band.
What is the difference between an external and an internal air receiver inspection?
An external inspection is done with the vessel in service: a competent person examines the shell, welds, supports and safety devices from the outside and reviews the records. An internal inspection requires the vessel to be depressurised, isolated and opened so the internal surfaces can be examined directly, with thickness testing where warranted. On air receivers the internal inspection is chiefly hunting corrosion where condensate sits, which cannot be seen from outside. Above pV 150 MPa·L the standard sets these at 2-yearly and 4-yearly respectively; at or below 150 MPa·L a competent person sets the intervals.
What inspection records do I need to keep for an air receiver?
Keep a register of the pressure equipment on site, the manufacturer’s design documentation, the commissioning record, the regulator registration or notification where required, and every in-service inspection report with its date, findings and the competent person’s details, plus maintenance and repair records. These records are the primary evidence of compliance in any audit, incident investigation or insurance claim. Under the model WHS Regulations, regulation 237 makes you hand them over when you relinquish control of plant that has to be registered. A receiver with years of service and no records may leave you unable to demonstrate compliance, whatever was actually done to it; Victoria expressly requires records to be kept for specified pressure vessels.
My air receiver has never been inspected. What should I do now?
Don’t wait for an audit to surface it. Establish the vessel’s design pressure and volume, work out the pV product, and engage a competent person to inspect the vessel and set its go-forward schedule. If the vessel is above 150 MPa·L and years overdue, expect the inspector to want an internal inspection early rather than waving it through. Rebuilding the file is a bounded, one-time exercise, and it’s dramatically cheaper than explaining the gap after an incident or a notice.