The irreversible humidity indicator is placed inside a package and always shows you the maximum measured relative humidity. The indicator field changes color from blue to pink when the humidity increases and retains this color permanently. The indicator consists of a special absorbent paper impregnated with various concentrated cobalt II chloride solutions. The impregnated surfaces show the relative humidity as a percentage. Moisture indicators are used in packaging with desiccants and barrier sleeves, which keep the relative humidity as low as possible during transportation.