Short answer: Class 0 pays off wherever compressed air touches the product, the packaging, or a regulated process — food contact, pharmaceutical process air, electronics, and air-jet weaving. It rarely pays off for general plant air, where a well-maintained oil-injected unit with proper filtration is the cheaper correct answer. AirSpace builds oil-free across three technologies from 2 HP to 315 HP, all rated to ISO 8573-1 Class 0 (per AirSpace series data, CE marked).
By Johnny Wayne, General Manager, AirSpace Machinery Co., Ltd. — 20 years in industrial compressed air systems. Reviewed by our engineering team.
The most expensive Class 0 specification we see is the one written for a machine shop. The most dangerous one is the Class 0 claim nobody tested. Between those two failures there is a narrow, well-defined set of duties where oil-free air is not a preference but a requirement — and this page is about drawing that line with numbers rather than adjectives.
What does ISO 8573-1 Class 0 actually mean?
Class 0 does not mean zero oil. That is the single most common misconception in compressed air specification, and it is worth correcting before anything else.
ISO 8573-1 sets purity classes for total oil content — liquid oil, oil aerosol and oil vapour together. Class 1 allows up to 0.01 mg/m³. Class 0 is defined as stricter than Class 1, with the actual limit agreed between the supplier and the user and verified by test (per ISO 8573-1:2010). Oil aerosol is measured per ISO 8573-2 and oil vapour per ISO 8573-5.
Three consequences follow, and we walk buyers through all three before quoting:
- A Class 0 claim without a test method is marketing. Ask which parts of ISO 8573 were used, at what point in the system, and at what ambient.
- The certificate describes the compressor, not your air. Oil in the delivered air can come from upstream ambient hydrocarbons, not from the machine. We have audited plants where the compressor was Class 0 and the pipework was not.
- Class 0 is a system property. Dryer selection, drain maintenance and pipe material decide whether the air arriving at the point of use matches what left the package.
Where does oil-free air actually touch the product?
Five duty types account for nearly every genuine Class 0 requirement we handle:
| Duty | Where the air goes | Why oil is disqualifying |
|---|---|---|
| Food and beverage | Product contact, pneumatic conveying, bottle blowing, packaging | Oil carry-over is a contaminant; BRC and equivalent audits test for it |
| Pharmaceutical | Process air, fermentation, coating, packaging | GMP expects air quality to be specified and verified, not assumed |
| Electronics and precision | Instrument air, component handling, cleanroom tools | Trace oil vapour deposits on surfaces and changes yield |
| Air-jet weaving | Weft insertion at the nozzle | Oil mist stains fabric — the defect shows up in the finished roll |
| Chemical and coatings | Catalyst protection, spray finishing | Oil poisons catalysts and causes fisheyes in paint |
The test we apply on site is simple: does this air end up inside, on, or immediately next to something the customer will inspect? If yes, oil-free is a process requirement. If the air drives a cylinder on a conveyor, it is not.
Which oil-free technology fits which duty?
AirSpace builds oil-free in three technologies, and the choice is driven by duty size and pressure rather than by brand preference. All ratings below are AirSpace published series data:
| Series | Power | Working pressure | Indicative FAD | Type / note |
|---|---|---|---|---|
| AP-OF-30 | 30 HP / 22 kW | 7–10 bar | 3.0–3.8 m³/min | Dry-type oil-free screw — ISO 8573-1 Class 0 / CE |
| AP-OF-50 | 50 HP / 37 kW | 7–10 bar | 5.0–6.2 m³/min | Dry-type oil-free screw — ISO 8573-1 Class 0 / CE |
| AP-OF-75 | 75 HP / 55 kW | 7–10 bar | 7.5–9.0 m³/min | Dry-type oil-free screw — ISO 8573-1 Class 0 / CE |
| AP-OF-100 | 100 HP / 75 kW | 7–10 bar | 10.0–12.2 m³/min | Dry-type oil-free screw — ISO 8573-1 Class 0 / CE |
| AP-OF-150+ | 150+ HP / 110+ kW | 7–10 bar | 15.0+ m³/min | Dry-type oil-free screw — ISO 8573-1 Class 0 / CE |
| AP-WL-30 | 30 HP / 22 kW | 7–10 bar | 3.0–3.8 m³/min | Water-injected screw — Class 0 |
| AP-WL-50 | 50 HP / 37 kW | 7–10 bar | 5.0–6.2 m³/min | Water-injected screw — Class 0 |
| AP-WL-75 | 75 HP / 55 kW | 7–10 bar | 7.5–9.5 m³/min | Water-injected screw — Class 0 |
| AP-WL-100 | 100 HP / 75 kW | 7–10 bar | 10.5–13.0 m³/min | Water-injected screw — Class 0 |
| AP-WL-315WPM | 315 HP / 250 kW | 7–10 bar | 38.0–45.0 m³/min | Water-injected PMV — Class 0, flagship |
| AS-VA-2 … AS-VA-10 | 2–10 HP / 1.5–7.5 kW | 8 bar | 0.16–0.92 m³/min | Oil-free scroll, ~40–50 dB(A) — point-of-use and lab duties |
How we steer the choice:
- Dry-type screw for the classic 30–150 HP plant duty where the air is a process input and the room is a normal compressor room.
- Water-injected screw when you want lower compression temperatures and large single-unit capacity — the AP-WL-315WPM covers 38–45 m³/min in one frame.
- Oil-free scroll for point-of-use and laboratory duty, where 40–50 dB(A) matters more than flow.
How do you specify Class 0 without overpaying?
Specify the requirement at the point of use, not at the package outlet, and separate the plant into zones. In our audits the pattern is nearly always the same: 80% of the air is general plant air, and 20% is critical. Sizing the whole compressor room to the critical 20% is where budgets go.
Five steps, in this order:
- Map which points of use touch product or process. Everything else leaves the specification.
- Set the class at the point of use and name the test method (ISO 8573-2 for aerosol, ISO 8573-5 for vapour).
- Decide zoned or centralised. A single oil-free unit plus a well-filtered general-purpose unit often beats one oversized oil-free package.
- Specify the dryer and the drains as part of the class, not as accessories.
- Ask for the audit evidence you will need — a BRC or GMP auditor will ask for the certificate and the test report, and we supply both with the package.
What does Class 0 cost to run?
Take a 75 kW duty at 7.5 bar, 6,000 h/yr, averaging 60% load — a typical food packaging profile.
Option A — oil-injected unit plus filtration to Class 0 quality. Coalescing and activated-carbon stages add differential pressure, and a 0.4 bar pressure drop across the filter train costs roughly 2.7% of compression energy (per 6–7% per bar across the 7–10 bar band):
- Base consumption: 45 kW × 6,000 h = 270,000 kWh/yr
- Filter pressure-drop penalty: +2.7% ≈ +7,300 kWh/yr ≈ 580 USD at 0.08 USD per kWh
- Element replacement, typically two full changes per year: 1,200–2,000 USD/yr (per typical element pricing and service intervals)
- Residual risk: oil carry-over after element breakthrough or a missed service — the cost is a rejected batch, not a line item
Option B — oil-free Class 0 package. No oil to remove, so no coalescing or carbon stage to buy, replace, or push air through. The capital cost is higher; the running cost is lower and the audit position is defensible with a certificate instead of a service log.
Our own field data puts the energy side of this on PM VSD frames at a 35% Energy Delta benchmark against a fixed-speed baseline of the same rating (per AirSpace part-load test data), and that applies to the oil-free PMV frames too.
What did the numbers look like in a real installation?
A Queensland food packaging facility supplying major supermarkets replaced legacy fixed-speed, oil-injected units with a single 75 HP AirSpace oil-free PMV Class 0 compressor. The measured result, published in the full case study:
- Energy: 378,000 kWh/yr down to 189,000 kWh/yr, worth 22,680 USD/yr in electricity.
- Maintenance: 4,500 USD/yr of filter and service cost eliminated.
- Audit: BRC passed first time, with a high-grade air quality rating — the outcome that was actually driving the project.
- Payback: 15 months.
Two honesty notes, because a buyer will find them anyway. First, that 50% energy reduction is a measured result on one installation with a poor legacy baseline, not our general benchmark — our published benchmark is the 35% Energy Delta under variable-demand profiles, and we would rather quote the conservative number. Second, part of that saving came from replacing fixed-speed machines with a PM VSD unit, not from oil-free alone.
When is Class 0 the wrong specification?
We turn down Class 0 enquiries regularly, and it is worth saying why:
- General plant air, tools, cylinders, conveyors. A maintained oil-injected unit with correct filtration is the right answer, and the difference buys a receiver or a leak survey.
- A plant that will not service the dryer. Class 0 from the package does not survive a saturated dryer or a failed drain.
- A duty where the audit does not require it. If no standard, customer code or process constraint names oil content, specifying Class 0 is spending capital on a property nobody will verify.
Key takeaways
- ISO 8573-1 Class 0 is stricter than Class 1 (0.01 mg/m³) with the limit agreed and tested — it is not “zero oil”, and any claim without a test method should be treated as marketing.
- Class 0 pays off where air touches product, packaging or a regulated process: food, pharma, electronics, air-jet weaving, and chemical/coatings duty.
- AirSpace oil-free spans 2 HP to 315 HP across scroll, dry-type screw and water-injected screw, at 7–10 bar (per AirSpace series data).
- Zone the plant before you buy: most plants need oil-free on 20% of their air, not all of it.
- The audit drives the project in food and pharma — a certificate plus test report is worth more than a lower kWh figure on its own.
Frequently asked questions
Is Class 0 the same as zero oil?
No. Per ISO 8573-1:2010, Class 0 is stricter than Class 1 (which permits up to 0.01 mg/m³ total oil), and the actual limit is agreed between supplier and user and verified by test. Oil aerosol is measured per ISO 8573-2 and oil vapour per ISO 8573-5.
Do I need an oil-free compressor for a food packaging line?
If the air contacts the product, the packaging, or the filling environment, yes — BRC and equivalent audits treat oil carry-over as a contamination risk, and one of our customers passed a BRC audit first time only after moving to oil-free (per the Queensland case study linked above).
What is the difference between dry-type and water-injected oil-free screw?
Dry-type screw compresses without any liquid in the chamber and relies on sealing and coating technology; water-injected screw uses water for sealing, cooling and lubrication, which keeps compression temperatures lower. Water-injected frames also scale larger — the AP-WL-315WPM covers 38.0–45.0 m³/min in a single unit.
Can I reach Class 0 with filters on an oil-injected compressor?
You can reach very low measured oil content, but the class then depends on element condition, differential pressure and service discipline rather than on the machine. That is a defensible position for some duties and a weak one in a GMP or BRC audit, where a certificate is easier to defend than a service log.
How much does oil-free air cost compared with filtered oil-injected air?
Higher capital, lower running cost. On a 75 kW duty at 6,000 h/yr, the filter route typically adds about 7,300 kWh/yr in pressure-drop penalty plus 1,200–2,000 USD/yr in element replacement (per 0.4 bar differential and two changes per year). The larger number is the batch you do not lose.
Sources and standards
- ISO 8573-1:2010 — compressed air purity classes; the definition of Class 0 and Class 1 (0.01 mg/m³ total oil) used throughout this page.
- ISO 8573-2 — test methods for oil aerosol content.
- ISO 8573-5 — test methods for oil vapour and organic solvent content.
- ISO 11011 — compressed air energy assessments; the basis for the duty figures above.
- ISO 9001 / CE marking — AirSpace quality system and conformity route; both verifiable on request.
- AirSpace oil-free ratings: published series data in the downloads library.
About the author
Johnny Wayne is General Manager of AirSpace Machinery Co., Ltd., and has spent 20 years in industrial compressed air systems. AirSpace manufactures from a 4,000 m² facility in Shanghai, ISO 9001:2015 certified and CE marked, and supplies oil-free packages from 2 HP scroll to 315 HP water-injected screw. He writes the specification guidance AirSpace engineers work from, and has taken Class 0 packages through BRC and GMP audits with customers in Australia, Europe and Southeast Asia.
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