DefinitionClass0isdefinedinApprovedDocumentB,AppendixA13;thisprovidestworoutestoenableamaterialtobedescribedasClass0.Thedefinitionisasfollows:ThehighestproductperformanceclassificationforliningmaterialsisClass0.Thisisachievedifamaterialorthesurfaceofacompositeproductiseither:-a)composedthroughoutofmaterialsoflimitedcombustibility,orb)aClass1materialwhichhasafirepropagationindex,(I)ofnotmorethan12,and(i1)ofnotmorethan6.Note:Class0isnotaclassificationidentifiedinanyBritishStandard.Caution:Ifyouchoosetogodownroutea),limitedcombustibilitymustbeproveninaccordancewithspecifiedteststandards.HowAreBS476Part6AndBS476Part7CombinedToProvide***ass0?ThedefinitionprovidedinApprovedDocumentB,AppendixA13;allowsthecombinationoftheBS476Part6andBS476Part7testresultsinordertoclassifyaliningproductasClass0(routeb).Initially,theBS476:Part7surfacespreadofflametestisconductedandthematerialmustobtainaClass1(i.e.mustnotspreadflametoadistanceofgreaterthan165mm,withtheexceptionofonespecimenwhichcanspreadflametoadistanceof190mm).Oncethisisachieved,theBS476:Part6firepropagationtestisconducted.Theindexofperformance,I,mustbe≤12(relatingtotheoveralltestperformance)andthesubindexofperformance,(i1),mustbe≤6(relatingtotheperformanceduringthefirstthreeminutesofthetest).Itisimportantthattheproductmustbetestedinexactlythesamemannerforbothoftheabovetests(e.g.materialsforbothtestsshouldbebondedusingthesameadhesiveandsubstrate,ifanairgapisusedinpracticeanairgapshouldbeusedinbothtests,etc.).)