You may have below questions when you're talking about air compressor and related piping installation:
 How to define air quality?
 What clean air means?
 Is there a standard to explain and communicate?

ISO 8573-1:2010 is such an international standard which explain & define the air quality 

by classifying oil, water, particulates content in air flow.

AIRpipe itself does not produce compressed air, in order to check the cleanness of pipe 

inner surface and any possible contamination from piping materials, a testing was carried 

out by an authorized 3rd party ROCKET AIR LABS in USA, the result is AIRpipe meets CLASS-1 

in all three contents: oil, water, particulates. (CLASS-0 is specified by equipment user or supplier 

and more stringent than CLASS-1)