Water vapour tightness
is the opposite of water vapour permeability.
When determining it, the water vapour permeability is measured. This is a measure of the impermeability of a packaging material.The water vapour permeability WDD is characterised by the amount of water vapour in g that diffuses through 1 m2 of sample area in 24 hours under specified conditions.Particularly in the case of organic barriers (plastics), the climate dependence of the results must be taken into account in order to obtain comparability.