For many applications, the measurement of Dew Point may be sufficient to prevent corrosion or failure in the distribution system by ensuring the water content in the air is below the point where it could condense out.
Oil can be a big problem in compressed air systems and testing for oil vapour can be a useful indicator of oil contamination as its presence often indicates the presence of liquid or aerosol oil as well.
Particle concentration measurements can indicate the effectiveness of filtration systems and indicate where filters are ready for replacement.
Testing for viable microbiologicals is vital for medical, food, beverage and pharmaceutical environments where contamination could endanger health.
These tests could be continuous, regularly scheduled or intermittent testing depending on the individual risk and plant standards.
ISO 8573 is a European standard currently comprised of 9 parts that describe all the types of contamination in compressed air, defining purity classes and appropriate methods of measurement.
ISO 8573-1: contaminants & purity classes
ISO 8573-2: oil aerosol test methods
ISO 8573-3: humidity test methods
ISO 8573-4: solid particle test methods
ISO 8573-5: oil vapour test methods
ISO 8573-6: gas test methods
ISO 8573-7: viable microbiological content tests
ISO 8573-8: solid particle test methods by mass concentration
ISO 8573-9: liquid water test methods
ISO 8573-1 defines purity classes for humidity, oil and particles which are the most common contaminants of concern to industrial users and relate to test methods in sections 2, 3, 4 & 5 of the standard.
For any measurement to be in accordance with the ISO 8573 purity classes, the test method must also be as described in the relevant section. If a method of testing is not covered in the standard then the results of that standard cannot be stated as being to ISO 8573 even if the test levels fall within the scope of the class.
This is particularly important for oil measurement as the purity class requires the measurement of all 3 phases - liquid, aerosol and vapour. If only one or two of the phases are measured, the result cannot be stated to be a particular 8573-1 purity class.
There is no legal requirement to test to this standard and simplified testing may well prove sufficient for monitoring trends and detecting issues for plant maintenance.