EPA Method 21

1151METHOD21-DETERMINATIONOFVOLATILEORGANICCOMPOUNDLEAKS1.0ScopeandApplication.1.1Analytes.AnalyteCASNo.VolatileOrganicCompounds(VOC)NoCASnumberassigned1.2Scope.ThismethodisapplicableforthedeterminationofVOCleaksfromprocessequipment.Thesesourcesinclude,butarenotlimitedto,valves,flangesandotherconnections,pumpsandcompressors,pressurereliefdevices,processdrains,open-endedvalves,pumpandcompressorsealsystemdegassingvents,accumulatorvesselvents,agitatorseals,andaccessdoorseals.1.3DataQualityObjectives.Adherencetotherequirementsofthismethodwillenhancethequalityofthedataobtainedfromairpollutantsamplingmethods.2.0SummaryofMethod.2.1AportableinstrumentisusedtodetectVOCleaksfromindividualsources.Theinstrumentdetectortypeisnotspecified,butitmustmeetthespecificationsandperformancecriteriacontainedinSection6.0.Aleakdefinitionconcentrationbasedonareferencecompoundisspecifiedineachapplicableregulation.Thismethodisintendedtolocateandclassifyleaksonly,andisnottobe1152usedasadirectmeasureofmassemissionratefromindividualsources.3.0Definitions.3.1CalibrationgasmeanstheVOCcompoundusedtoadjusttheinstrumentmeterreadingtoaknownvalue.Thecalibrationgasisusuallythereferencecompoundataknownconcentrationapproximatelyequaltotheleakdefinitionconcentration.3.2Calibrationprecisionmeansthedegreeofagreementbetweenmeasurementsofthesameknownvalue,expressedastherelativepercentageoftheaveragedifferencebetweenthemeterreadingsandtheknownconcentrationtotheknownconcentration.3.3LeakdefinitionconcentrationmeansthelocalVOCconcentrationatthesurfaceofaleaksourcethatindicatesthataVOCemission(leak)ispresent.Theleakdefinitionisaninstrumentmeterreadingbasedonareferencecompound.3.4NodetectableemissionmeansalocalVOCconcentrationatthesurfaceofaleaksource,adjustedforlocalVOCambientconcentration,thatislessthan2.5percentofthespecifiedleakdefinitionconcentration.thatindicatesthataVOCemission(leak)isnotpresent.11533.5ReferencecompoundmeanstheVOCspeciesselectedastheinstrumentcalibrationbasisforspecificationoftheleakdefinitionconcentration.(Forexample,ifaleakdefinitionconcentrationis10,000ppmasmethane,thenanysourceemissionthatresultsinalocalconcentrationthatyieldsameterreadingof10,000onaninstrumentmetercalibratedwithmethanewouldbeclassifiedasaleak.Inthisexample,theleakdefinitionconcentrationis10,000ppmandthereferencecompoundismethane.)3.6ResponsefactormeanstheratiooftheknownconcentrationofaVOCcompoundtotheobservedmeterreadingwhenmeasuredusinganinstrumentcalibratedwiththereferencecompoundspecifiedintheapplicableregulation.3.7ResponsetimemeansthetimeintervalfromastepchangeinVOCconcentrationattheinputofthesamplingsystemtothetimeatwhich90percentofthecorrespondingfinalvalueisreachedasdisplayedontheinstrumentreadoutmeter.4.0Interferences.[Reserved]5.0Safety.5.1Disclaimer.Thismethodmayinvolvehazardousmaterials,operations,andequipment.Thistestmethodmaynotaddressallofthesafetyproblemsassociatedwithits1154use.Itistheresponsibilityoftheuserofthistestmethodtoestablishappropriatesafetyandhealthpracticesanddeterminetheapplicabilityofregulatorylimitationspriortoperformingthistestmethod.5.2HazardousPollutants.Severalofthecompounds,leaksofwhichmaybedeterminedbythismethod,maybeirritatingorcorrosivetotissues(e.g.,heptane)ormaybetoxic(e.g.,benzene,methylalcohol).Nearlyallarefirehazards.Compoundsinemissionsshouldbedeterminedthroughfamiliaritywiththesource.Appropriateprecautionscanbefoundinreferencedocuments,suchasreferenceNo.4inSection16.0.6.0EquipmentandSupplies.AVOCmonitoringinstrumentmeetingthefollowingspecificationsisrequired:6.1TheVOCinstrumentdetectorshallrespondtothecompoundsbeingprocessed.Detectortypesthatmaymeetthisrequirementinclude,butarenotlimitedto,catalyticoxidation,flameionization,infraredabsorption,andphotoionization.6.2Theinstrumentshallbecapableofmeasuringtheleakdefinitionconcentrationspecifiedintheregulation.11556.3Thescaleoftheinstrumentmetershallbereadableto±2.5percentofthespecifiedleakdefinitionconcentration.6.4Theinstrumentshallbeequippedwithanelectricallydrivenpumptoensurethatasampleisprovidedtothedetectorataconstantflowrate.Thenominalsampleflowrate,asmeasuredatthesampleprobetip,shallbe0.10to3.0l/min(0.004to0.1ft3/min)whentheprobeisfittedwithaglasswoolplugorfilterthatmaybeusedtopreventpluggingoftheinstrument.6.5Theinstrumentshallbeequippedwithaprobeorprobeextensionforsamplingnottoexceed6.4mm(1/4in)inoutsidediameter,withasingleendopeningforadmissionofsample.6.6TheinstrumentshallbeintrinsicallysafeforoperationinexplosiveatmospheresasdefinedbytheNationalElectricalCodebytheNationalFirePreventionAssociationorotherapplicableregulatorycodeforoperationinanyexplosiveatmospheresthatmaybeencounteredinitsuse.Theinstrumentshall,ataminimum,beintrinsicallysafeforClass1,Division1conditions,and/orClass2,Division1conditions,asappropriate,asdefinedbytheexamplecode.Theinstrumentshallnotbeoperatedwithanysafetydevice,suchasanexhaustflamearrestor,removed.11567.0ReagentsandStandards.7.1Twogasmixturesarerequiredforinstrumentcalibrationandperformanceevaluation:7.1.1ZeroGas.Air,lessthan10pa