ISO 15496:2018 describes a comparatively simple method for testing the water vapour permeability of textiles that will provide the manufacturer with a clearly recognized method for quality control within the plant.
The simple test method described in this document is not applicable for classifying the water vapour resistance of textiles against values relating to physiological effects specified in product standards, and particularly not those relating to personal protective equipment.
ISO 15496:2018 cannot be used to compare results to other "dry dessicant" methods as they will not correlate. An explanation of the reasons can be found in Annex C.