permeation tube

https://doi.org/10.1351/goldbook.P04506
A device used for dynamic preparation of test gas mixtures by means of controlled permeation of a gaseous analyte out of a container through polymer material into a @[email protected] stream. These devices containing certain condensable gases (e.g. NO2 , SO2 , etc.) when operated at closely controlled temperatures can be used as primary standards calibrated in terms of the @[email protected] loss per unit time.
Source:
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2205 [Terms] [Paper]