Standard ISO 8573-1:2010

… the „mother“ of all compressed air treatment standards

The subject of the ISO 8573 series is the compressed air purity at any specific point of a compressed air system (downstream after-cooler). The ISO 8573 series defines standardized and manufacturer independent measuring methods for contaminations in compressed air and methods to express the required or measured compressed air purity.

ISO 8573-1  – a Standard of Compressed Air Quality
It is group of international standards concerning compressed air quality.
Standard consists of 9 parts. Nr. 1 defines quality requirements on compressed air,
parts Nr. 2 – 9 describe testing methods of many contaminants in the air.

PDP… pressure dew point


The individual parts of the standard deal with:

8573-1. Contaminants and purity classes

8573-2. Oil aerosol content

8573-3. Test methods for measurement of humidity

8573-4. Test methods for particle content

8573-5. Test methods for oil vapour and organic solvent content

8573-6. Test methods for gaseous contaminant content

8573-7. Test methods for viable microbiological contaminant content

8573-8. Test methods for solid particle content by mass concentration

8573-9. Test methods for liquid water content


The compressed air purity for the three major contaminants in compressed air, expressed as ISO 8573-1 purity classes, is stated in the following way:

ISO 8573-1:2010 [ A : B : C ]

 A – is the purity class for particles

B – is the purity class for humidity and liquid water

C – is the purity class for the total oil content

When a class for any of the three major contaminants is not specified, the designation shall be replaced by a hyphen, e.g.

     ISO 8573-1:2010 [ A :  : C ]

for a compressed air purity without any requirements to the humidity or water content.

When a specified contamination level falls within class X, then the highest concentration shall be given in round brackets, e.g.

     ISO 8573-1:2010 [ A : X(15) : C ]

for a maximum concentration of liquid water of 15 g/m³.

When a specified contamination level falls within class 0, IT IS MANDATORY to state the highest allowable concentration (which must be better than defined for class 1), e.g.

 ISO 8573-1:2010 [ 0(1000:100:1) : 0(-80) : 0(0,001) ]


 ISO 8573-1:2010 [ 0 : 0 : 0 ]

Maximum particle content: 1000 pcs/m³ (0,1-0,5µ), 100 pcs/m³ (0,5-1µ), 1 pcs/m³ (1-5µ)
Maximum humidity : -80°C (PDP)
Maximum total oil content: 0,001 mg/m³

The designation itself is not defined for class 0, so it can be expressed in separate ways.