Dry air and dry nitrogen purges pull moisture from the test space to create a less humid chamber environment.
The dry air purge features a desiccant dehumidifier that pulls moisture from the air using an active desiccant material and a hygroscopic substance that induces dryness in its vicinity. As the ultra-dry nitrogen, which has a dewpoint of -70 degrees Celcius, is introduced into the enclosed cavity, it expands and places the test item under pressure, removing any residual moisture from the test product and internal test chamber environment.
Desiccant dehumidifiers have a more complex principle of operation but perform exceptionally well in colder climates or when there is a large amount of moisture in the air.
Temperature and humidity environmental test chambers are commonly paired with dry air purge systems, which reduce the humidity index of the chamber interior at a much quicker rate than a natural rate.
Temperature-only chambers may also benefit from a dry air purge system if the user wishes to control the residual moisture that is generated with temperature changes within the chamber interior.
Dry nitrogen may also be used as a dry gas purge method.