ISO 8573-1 Air Quality Classes: Tables, Codes & AU Guide

By Byron Raal, CAS Founder-Editor · Last updated 25 June 2026 · About the author

ISO 8573-1 is the language compressed-air engineers use to specify how clean the air actually needs to be. Three contaminants get classified: solid particulate, water, oil. Numbered classes 0 to 9 (or X) for each. Used right, it’s the only honest way to compare one supplier’s quote against another’s.

What it isn’t: a regulation. ISO 8573-1 doesn’t tell you what class to run. Your process risk does. Medical breathing air? AS 2568:2019 Incorporating Amendment 1 binds. Surgical-tool air? AS 2896:2021 governs. Pharmaceutical sterile-product contact? PIC/S PE 009-17 Annex 1 risk-based framework. Food contact? FSANZ Food Standards Code. The regulator standard sets the legal target. ISO 8573 is the mechanical language you use to specify and audit how you hit it.

Most ISO 8573 quotes in the Australian market are wrong because they leave half the standard out. You’ll see “Class 2.4.1” on a supplier datasheet with no mention of the >5 µm void clause, no breakdown of which contaminant actually got tested, no acknowledgement that microbiologicals and gases sit outside the class system entirely. This page is the whole standard in plain English. Read it before you sign a procurement contract or accept a commissioning certificate, then audit your supplier against it.

Table 1: Solid particulate classes

Explainer of ISO 8573-1 Class X.Y.Z notation, showing the three separate classes for particles, water and oil, example 1.2.1. - by Compressed Air Solutions, licensed CC BY 4.0.

ISO 8573-1:2010 Table 1 specifies maximum particle counts per cubic metre across three size ranges (0.1-0.5 µm, 0.5-1.0 µm, 1.0-5.0 µm). Classes are numbered 0 through 9, with stricter classes numbered lower. Verbatim from the publisher-source supplement:

ISO 8573-1:2010 Cl 6.1 (Designation principle) specifies the formal combined-class notation as three numbers separated by colons in the order particulate, humidity/water, oil:

ISO 8573-1:2010 [A:B:C]

ISO 8573-1 compressed air class cascade diagram - by Compressed Air Solutions, licensed CC BY 4.0.

Where A is particulate class (per Table 1), B is humidity/water class (per Table 2), and C is oil class (per Table 3). Example: “ISO 8573-1:2010 [2:4:1]” means Class 2 particulate + Class 4 water + Class 1 oil.

Industry catalogues, supplier datasheets, and engineering documents frequently use a dot-separated form (“Class 2.4.1”) as a shorthand. The dot form is widely accepted in trade communication but is not the ISO-mandated format. For formal compliance documentation, audit reports, and validation records, use the colon-separated [A:B:C] format per ISO 8573-1:2010 Cl 6.1.

When a class for any particular contaminant A, B, or C is not specified, Cl 6.2 specifies the designation shall use a hyphen (e.g., “ISO 8573-1:2010 [A:-:C]” where there is no humidity classification). When the contamination level falls within class X, Cl 6.3 specifies the highest concentration of the contaminant shall be given in round brackets (e.g., “ISO 8573-1:2010 [A:X(15):C]” where Cw = 15 g/m³).

This combined notation is more informative than a single-number label. When a supplier quotes “ISO 8573-1 Class 1”, it is ambiguous which contaminant they mean. Always require the three-number notation.

Need help with ISO 8573-1 specification or audit?

Tell us your application (medical, surgical-tool, pharmaceutical, food contact, breathing-air respirator, general industrial) and your ISO class target. We connect you with an Australian compressed air designer who works in your regulatory regime daily and audits at the outlet, not the OEM’s preferred sample point. Independent matching. Direct email acknowledgement within one business day; supplier match or status update within five business days.

Describe Your Application

How ISO 8573-1 relates to AU regulator-prescribed standards

AS 2568:2019 IncAmd 1 (medical breathing air): Table 1 prescribes specific contaminant limits including dewpoint ≤ +5 °C at pipeline pressure. AS 2568 dewpoint sits between ISO 8573-1 Class 4 (+3 °C) and Class 5 (+7 °C); calling AS 2568 medical breathing air “Class 4” or “Class 5” is engineering shorthand at best, not strictly compliant for documentation. AS 2568 governs.
AS 2896:2021 Cl 2.11.2 (surgical-tool air): sets moisture at ≤ 60 ppm (vol), which corresponds to roughly ISO 8573-1 Class 3 for water vapour (a pressure dewpoint near -30 °C). Audit against that 60 ppm volume limit itself, not a converted ISO dewpoint class. Note: Cl 5.4.7 (a separate clause) is the particulate matter test methodology used during MGPS commissioning, redirected to from AS 2568 Amendment 1 Item 6, not the surgical-tool air spec.
PIC/S PE 009-17 (pharmaceutical): risk-based, not class-prescriptive. Manufacturer’s Quality Risk Management documents the chosen target (often expressed as ISO 8573-1 class) and validates achievement.
FSANZ Food Standards Code: does not prescribe ISO classes; the site’s Food Safety Program selects the appropriate target.
AS 1715/AS 1716 (breathing-grade air for respiratory protection): specific contaminant limits; ISO 8573-1 not a substitute.

Common errors with ISO 8573-1

Quoting a single ISO class number without specifying which contaminant. Per ISO 8573-1:2010 Cl 6.1, the formal designation uses colons inside brackets, e.g., “ISO 8573-1:2010 [1:4:1]” for Class 1 particulate, Class 4 water, Class 1 oil; the dot-separated form “1.4.1” is widely used in trade communication but is not the ISO-mandated format.
Treating ISO 8573-1 as regulator-binding for a specific application; it is the engineering-target framework, not the regulator-prescribed standard.
Citing “ISO 8573-1 Class 0” without documenting the specific user-defined particulate-count or oil-content target.
Quoting Classes 1/2/3 as -60/-50/-40 °C dewpoint (incorrect; correct values are -70/-40/-20 °C).
Using a refrigerated dryer to deliver Class 1, 2, or 3 water; refrigerated dryers physically cap at approximately +3 °C PDP (Class 4). Lower classes require desiccant adsorption.
Citing oil Class X as > 10 mg/m³ (Parker and Atlas Copco whitepapers do this). The standard says > 5. The > 10 figure is particulate Class X mass concentration from Table 1, not oil.
Quoting a “microbiologically clean” or “microbio-free” ISO class. There is no ISO 8573-1 class for microbiologicals: Part 7 measures cfu/m³, reported as a separate addendum to the [A:B:C] designation.
Treating an ISO 8573-1 Class 2.4.1 result on legacy galvanised distribution as compliant without testing the >5 µm void clause from §5.2.

Sourcing ISO 8573-1 specification expertise

You spec ISO 8573 once. You live with it for 15 years. The early decision determines whether your facility actually delivers the air your process needs, or whether you find out at audit time that your Class 2.4.1 quote was a label, not a measurement.

What independent expertise actually looks like:

A designer who maps your regulator-prescribed standard to an ISO 8573 target. If your designer hands you “Class 1.2.1” without showing how it satisfies AS 2568, AS 2896, PIC/S, or FSANZ for your application, they’ve punted the design responsibility. Get a fresh designer.
Independent witness testing at the point of use, not at the compressor room. Per ISO 8573-2 (oil aerosol), -3 (humidity), -4 (solid particle), -5 (oil vapour), -6 (gas), -7 (microbio). OEMs test under idealised conditions immediately downstream of their kit. Your reality is 200 metres of legacy pipework, dead legs, and shared-use drops. The >5 µm void clause from §5.2 voids your Class quote if your distribution sheds. Test at the outlet.
Validation records that capture measured outlet performance, not equipment ratings. ISO 8573 is performance-stated. If your validation file holds only dryer and filter ratings, you don’t have a validated system. You have a brochure.

CAS introduces independent compressed-air designers and validators across Australia who match your regulatory regime. Tell us your application and your ISO class target. We connect you with someone who works in that regime daily and audits at the outlet.

Standards and references

ISO 8573-1:2010 catalogue: full text of the contaminant classes standard.
Standards Australia: AS 2568:2019 Incorporating Amendment 1, AS 2896:2021, AS 1715, AS 1716, AS/NZS 3788:2024 Incorporating Amendment No. 1 catalogue access.
Food Standards Australia New Zealand: Food Standards Code Chapter 3 risk-based food safety standards (does not prescribe ISO 8573 classes; food contact air managed under the food business’s HACCP plan).

Frequently Asked Questions

What does ISO 8573-1 Class 0 mean?

Class 0 is user-defined. ISO 8573-1:2010 Table 1 footnote (particulate) and Table 3 (oil) both specify that Class 0 is whatever the user documents as a target tighter than Class 1. There is no fixed Class 0 limit set by the standard. A supplier offering ‘Class 0 oil-free’ without documenting the specific oil-content target in mg/m³ is selling a marketing label, not a measurable engineering target. Pharmaceutical and semiconductor manufacturers typically specify Class 0 with parts-per-billion residual targets and validate via ISO 8573-2 oil-aerosol test methods.

What are the ISO 8573-1 water classes by pressure dewpoint?

ISO 8573-1:2010 Table 2 specifies pressure dewpoint (PDP) limits: Class 1 ≤ -70 °C, Class 2 ≤ -40 °C, Class 3 ≤ -20 °C, Class 4 ≤ +3 °C, Class 5 ≤ +7 °C, Class 6 ≤ +10 °C. Classes 7-9 cover liquid-water concentration (Cw, g/m³) for saturated states: Class 7 Cw ≤ 0.5, Class 8 0.5 u003c Cw ≤ 5, Class 9 5 u003c Cw ≤ 10. Common error: citing Classes 1/2/3 as -60/-50/-40 °C is wrong. The correct values are -70/-40/-20 °C.

What does the ISO 8573-1 [A:B:C] designation actually mean?

Per ISO 8573-1:2010 Cl 6.1 (Designation principle), the formal combined-class notation is three numbers separated by colons in the order particulate, humidity/water, oil: ISO 8573-1:2010 [A:B:C]. Example: [2:4:1] means Class 2 particulate plus Class 4 water plus Class 1 oil. Industry frequently uses a dot form (Class 2.4.1) as shorthand; this is widely accepted in trade but not the ISO-mandated format. For formal compliance documentation use the colon-separated [A:B:C] notation. Cl 6.2 specifies a hyphen where a class is unspecified; Cl 6.3 specifies bracket notation for Class X concentration.

How does AS 2568 medical breathing air map to ISO 8573-1?

AS 2568:2019 Incorporating Amendment 1 prescribes specific contaminant limits for medical breathing air, including dewpoint ≤ +5 °C at pipeline pressure. The +5 °C target sits between ISO 8573-1 Class 4 (+3 °C) and Class 5 (+7 °C); calling AS 2568 medical breathing air ‘Class 4’ or ‘Class 5’ is engineering shorthand at best, not strictly compliant for medical-air documentation. AS 2568 is the regulator-prescribed standard for medical breathing air in Australia and governs. Use ISO 8573 as the mechanical specification language; cite AS 2568 verbatim for the regulatory target.

What are the most common ISO 8573-1 specification errors?

Eight recurring errors: quoting a single ISO class number without specifying which contaminant; treating ISO 8573-1 as regulator-binding (it is the engineering target, not the regulator); citing Class 0 without documenting the specific user-defined target; misquoting water class dewpoints as -60/-50/-40 °C (correct: -70/-40/-20 °C); using a refrigerated dryer to deliver Class 1, 2, or 3 water (physically capped at +3 °C PDP); citing oil Class X as u003e 10 mg/m³ (correct: u003e 5; the u003e 10 figure is particulate Class X mass concentration from Table 1); quoting microbiologically-clean ISO class (no such thing; Part 7 measures cfu/m³ separately); treating Class 2.4.1 results on legacy galvanised distribution as compliant without the u003e5 µm void clause check from §5.2.

Book a point-of-use ISO 8573 audit

Before you commission, before you replace a dryer, or before your next regulatory cycle. Email byron@compressedairsolutions.com.au with your site postcode and application regime. Independent designer matching. Acknowledgement within one business day. Supplier match or status update within five business days.

Get Matched with an Expert

Related Resources

Compressed Air Dryers and Air Quality: dryer technology selection by ISO water class target.
Dew Point Calculator: convert between PDP and atmospheric dewpoint at your operating pressure.
Refrigerated vs Desiccant Dryer: side-by-side comparison for selecting against your ISO water class target.
TGA Pharmaceutical Compressed Air Compliance: PIC/S PE 009-17 mapping for pharmaceutical sterile-product contact air.
FSANZ Food Contact Compressed Air Requirements: HACCP-based selection of ISO class for food contact applications.
Compressed Air for Medical and Dental Facilities: AS 2568 medical breathing air + AS 2896 surgical-tool air mapping.
Compressed Air for Pharmaceutical Manufacturing: PIC/S risk-based ISO class selection for sterile manufacturing.
Compressed Air for Food Processing: ISO class selection by food contact risk tier.
Air Compressor Sizing Guide: sizing methodology including ISO class target inputs.

General information disclaimer. The information on this page is general in nature and provided for educational purposes only. It is not engineering, safety, or professional advice, and it does not account for the specifics of your site, equipment, or duty. Compressed air system design, pressure equipment selection, and regulatory compliance must be confirmed with a qualified engineer and the relevant work health and safety regulator before you act. Compressed Air Solutions is a publisher and referral service, not a licensed engineering practice, and accepts no liability for decisions made on the basis of this content. Verify all figures, standards references, and regulatory requirements against current primary sources.