Quality of compressed air is a broad term. One person may deem his compressed air quality as “poor” if he finds water at the end-use point. Another may tell you that her compressed air is high quality because she is able to maintain a dew point temperature at –40°F or lower. As with any measurement, in order to be consistent, we must have a reference for comparison. In the world of compressed air, the most common reference is ISO 8573.1.

The quality of compressed air is determined primarily by measuring three contaminants: solid particles as measured by their size or concentration, water vapor content as measured by pressure dew point temperature, and oil content as measured by concentration. The contamination level is influenced by the type of compressor, dryer, filtration, and other related components used. A higher quality of air in any of these categories usually equates to more expensive equipment.

A more subjective qualification of compressed air divides air quality into one of four categories: power air, instrument air, process air or breathing air.

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