ASTM_D_3609_-_00_2014.pdf

Designation:D360900(Reapproved 2014)Standard Practice forCalibration Techniques Using Permeation Tubes1This standard is issued under the fixed designation D3609;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice describes a means for using permeationtubes for dynamically calibrating instruments,analyzers,andanalytical procedures used in measuring concentrations ofgases or vapors in atmospheres(1,2).21.2 Typical materials that may be sealed in permeation tubesinclude:sulfur dioxide,nitrogen dioxide,hydrogen sulfide,chlorine,ammonia,propane,and butane(1).1.3 The values stated in SI units are to be regarded asstandard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:3D1356 Terminology Relating to Sampling and Analysis ofAtmospheresD3195 Practice for Rotameter Calibration3.Terminology3.1 DefinitionsRefer to Terminology D1356.4.Summary of Practice4.1 Aliquefiable gas,when enclosed in an inert plastic tube,escapes by permeating the tubing wall at a constant,reproducible,temperature-dependent rate.4.2 Permeation tubes are calibrated gravimetrically,with theweight loss of the tube equated to the weight of the escapingmaterial.4.3 Permeation tubes are held at constant temperature in acarrier-gas stream of dry air or nitrogen to produce a gasconcentration dependent on the permeation rate and the flow ofthe carrier gas.5.Significance and Use5.1 Most analytical methods used in air pollutant measure-ments are comparative in nature and require calibration orstandardization,or both,often with known blends of the gas ofinterest.Since many of the important air pollutants are reactiveand unstable,it is difficult to store them as standard mixtures ofknown concentration for extended calibration purposes.Analternative is to prepare dynamically standard blends as re-quired.This procedure is simplified if a constant source of thegas of interest can be provided.Permeation tubes provide thisconstant source,if properly calibrated and if maintained atconstant temperature.Permeation tubes have been specified asreference calibration sources,for certain analytical procedures,by the Environmental Protection Agency(3).6.Interferences and Precautions6.1 Permeation tubes are essentially devices to provide aconstant rate of emission of a specific gaseous substance overperiod of time.They consist of a two-phase(gas-liquid)systemto maintain a constant vapor pressure(at constant temperature)which is the driving force for emission of the gas through asemipermeable membrane(tube walls).They can be expectedto maintain a constant emission rate that is temperaturedependent as long as a significant amount of liquid is presentin the device.The liquid shall be pure,else its composition maychange during the life time of the tube,due to differentialevaporation,with consequent vapor pressure changes.Caremust also be exercised that the diffusion membrane(tubewalls)is not damaged or altered during use.The contents ofpermeation tubes are under relatively high pressure.Accordingly,there is the possibility of violent rupture of tubewalls under high temperature exposure.Permeation rates havetemperature coefficients up to 10%per degree Celsius.Whentemperature coefficients are large,above 3%per degreeCelsius,stringent temperature control is required.Furthermorepermeation tubes exhibit temperature hysteresis so that theymust be temperature equilibrated from 2 to 24 h before use,depending upon the temperature differential between storageand use(4).It is important that permeation tubes are filled with1This practice is under the jurisdiction ofASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.01 on Quality Control.Current edition approved Sept.1,2014.Published September 2014.Originallyapproved in 1977.Last previous edition approved in 2010 as D3609 00(2010).DOI:10.1520/D3609-00R14.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 anhydrous constituents of high purity.They shall be handledwith care to minimize contact with moisture,oil,and foreignsubstances.6.2 Sulfur dioxide(SO2)permeation tubes are relativelyinsensitive