ISO 2556:1974

Specification of the methodand of two types of suitable test apparatus. The plastic test specimen separates two chambers, the one contains the test gas at atmospheric pressure, the other of known initial volume has the air pumped out until the pressure is practically zero. The quantity of gas which passes through the specimen from one chamber to the other is determined as a function of time by measuring the increase in pressure occuring in the second chamber by means of a manometer.