Depending on the method and specific apparatus employed, materials up to 38 mm thick and with water vapour transmission rates in the range 0,05 g/(m^2.d) to 65 g/(m^2.d) can be tested. The basis of the function of the instrumental techniques is briefly described. Advice on calibration is given in annex B. Specifies principle, apparatus, sampling, preparation of test pieces, procedure, expression of results, precision and test report.