Industrial Utility Efficiency    

Parker Releases White Paper on ISO 8573-1 Class 0

There are three ISO standards currently in use directly relating to compressed air quality (purity) and testing. The most commonly used air quality standard is the ISO8573 Series, consisting of nine separate parts. Part 1 relates to the quality classifications for compressed air by specifying the amount of contamination allowed in each cubic meter of compressed air. Parts 2-9 specify the methods of testing a compressed air system for one or more common contaminants. 

ISO 8573-1 breaks compressed air contaminants in three major groups: Particulate, Water and Total Oil. Different levels of contamination (per cubic meter) are then assigned “Purity Classes.”

 Classification solid particulate

Easy to use classification table for solid particulate, water and total oil. Click here to enlarge.

Unfortunately, the ISO 8573-1 Class 0 classification is often misapplied to air compressors or treatment products (almost all oil-free compressors are sold under the banner of Class 0). It is often implied in marketing literature that:

  • Class 0 means zero contamination in the compressed air
  • Class 0 refers to oil contamination only
  • A Class 0 compressor guarantees totally oil free compressed air

When referring to ISO8573-1 Class 0, it is important to remember:

  • Class 0 does not mean zero contamination
  • Class 0 does not mean oil-free compressed air
  • A Class 0 compressor does not guarantee oil-free compressed air
  • Class 0 does not solely refer to oil contamination
  • A Class 0 specification must be ‘cleaner’ than the Class 1 specification for the contaminant chosen
  • The contamination levels stated for a Class 0 specification must also be within the measurement capabilities of the test equipment and test methods shown in ISO 8573 Part 2-9
  • The Class 0 specification must clearly state which contaminant the Class 0 claim refers to - i.e. “Solid Particulate,” “Water” or “Total Oil (aerosol, liquid & vapor)”
  • Class 0 requires the user or the equipment supplier to show a contamination level as part of a written specification

To learn more about ISO 8573-1, visit to download the Introduction to ISO 8573-1 White Paper by Mark White, Compressed Air Treatment Applications Manager at Parker Hannifin. Within it, he explains common myths surrounding the ISO8753-1-Class 0 Standard, and what you need to know when specifying air purity.


About Parker Hannifin

Parker Hannifin is a Fortune 250 global leader in motion and control technologies. For 100 years the company has engineered the success of its customers in a wide range of diversified industrial and aerospace markets. Learn more at