ISO 8573-3 introduces several test methods to determine the content of humidity in compressed air, describing the typical range of application and limitations of each method.
|Applying one of the test methods of ISO 8573-3 is mandatory for the allocation of a purity class according to ISO 8573-1.|
ISO 8573-3 doesn’t demand a specific method, but the proper selection of a suitable method for the intended measurement task as well as related measuring device according to the manufacturer’s declaration.
Beside a lot of useful information about humidity measurement, ISO 8573-3 provides a professional method for the calculation of the saturated water vapor pressure in compressed air in its Annex B.
ISO 8573-3 defines the reference condition for humidity statements in compressed air as
«7 bar(e) and 20°C, unless otherwise agreed».
In practice, humidity statements are typically referred to the actual working conditions (pressure, temperature) during the measurement period – without any further reference statement and thus actually non-compliant to ISO 8573-3.