ISO 8573 air quality class

ISO 8573 is the global standard for compressed-air purity. It defines class numbers (0-9) across three contaminant categories: solid particles, water (humidity and liquid), and total oil (aerosol, liquid, and vapor). A complete spec is written as three numbers, like “Class 1.2.1” — read as Class 1 particles, Class 2 water, Class 1 oil.

What it is

The standard replaces older, manufacturer-specific terminology with a single number set everyone can verify. Class 0 in oil specifically denotes “better than Class 1, as agreed between supplier and user,” which in practice means certified oil-free machines. ISO 8573 also defines the measurement methods (8573-2 through -9) so claims are auditable.

Why it matters

Specifying a compressed-air system without ISO 8573 classes leaves filtration and dryer sizing open to interpretation. With classes, a pharmaceutical plant can write “Class 1.2.1 at all points of use” into a procurement spec and hold every vendor to a single bar. The standard maps directly onto filter and dryer ratings; manufacturers publish class deliverables in CAGI data sheets.

How it is used in our catalog

Each dryer and filtration unit publishes the ISO 8573 class it delivers at rated inlet conditions. Critical-application class pages (food, pharma, electronics) cross-reference the required ISO 8573 envelope. The breathing-air class page covers grade-D and Class 0 oil specifically.

Common questions

What is the difference between Class 0 and Class 1 oil?

Class 1 is 0.01 mg/m3 total oil. Class 0 is “better than Class 1, as agreed” — typically a certified oil-free compressor with no oil in the compression chamber.

Is Class 1.2.1 standard for instrument air?

ANSI/ISA-7.0.01 instrument air aligns to roughly ISO 8573 Class 2.3.3 or better; Class 1.2.1 is a common premium spec.