Chapter44-IndoorAirQualityINDOORAIRQUALITY:INTRODUCTIONXavierGuardinoSoláTheconnectionbetweentheuseofabuildingeitherasaworkplaceorasadwellingandtheappearance,incertaincases,ofdiscomfortandsymptomsthatmaybetheverydefinitionofanillnessisafactthatcannolongerbedisputed.Themainculpritiscontaminationofvariouskindswithinthebuilding,andthiscontaminationisusuallyreferredtoas“poorqualityofindoorair”.Theadverseeffectsduetopoorairqualityinclosedspacesaffectaconsiderablenumberofpeople,sinceithasbeenshownthaturbandwellersspendbetween58and78%oftheirtimeinanindoorenvironmentwhichiscontaminatedtoagreaterorlesserdegree.Theseproblemshaveincreasedwiththeconstructionofbuildingsthataredesignedtobemoreairtightandthatrecycleairwithasmallerproportionofnewairfromtheoutsideinordertobemoreenergyefficient.Thefactthatbuildingsthatdonotoffernaturalventilationpresentrisksofexposuretocontaminantsisnowgenerallyaccepted.Thetermindoorairisusuallyappliedtononindustrialindoorenvironments:officebuildings,publicbuildings(schools,hospitals,theatres,restaurants,etc.)andprivatedwellings.Concentrationsofcontaminantsintheindoorairofthesestructuresareusuallyofthesameorderasthosecommonlyfoundinoutdoorair,andaremuchlowerthanthosefoundinairinindustrialpremises,whererelativelywell-knownstandardsareappliedinordertoassessairquality.Evenso,manybuildingoccupantscomplainofthequalityoftheairtheybreatheandthereisthereforeaneedtoinvestigatethesituation.Indoorairqualitybegantobereferredtoasaproblemattheendofthe1960s,althoughthefirststudiesdidnotappearuntilsometenyearslater.Althoughitwouldseemlogicaltothinkthatgoodairqualityisbasedonthepresenceintheairofthenecessarycomponentsinsuitableproportions,inrealityitistheuser,throughrespiration,whoisthebestjudgeofitsquality.Thisisbecauseinhaledairisperceivedperfectlythroughthesenses,ashumanbeingsaresensitivetotheolfactoryandirritanteffectsofabouthalfamillionchemicalcompounds.Consequently,iftheoccupantsofabuildingareasawholesatisfiedwiththeair,itissaidtobeofhighquality;iftheyareunsatisfied,itisofpoorquality.Doesthismeanthatitispossibletopredictonthebasisofitscompositionhowtheairwillbeperceived?Yes,butonlyinpart.Thismethodworkswellinindustrialenvironments,wherespecificchemicalcompoundsrelatedtoproductionareknown,andtheirconcentrationsintheairaremeasuredandcomparedwiththresholdlimitvalues.Butinnonindustrialbuildingswheretheremaybethousandsofchemicalsubstancesintheairbutinsuchlowconcentrationsthattheyare,perhaps,thousandsoftimeslessthanthelimitssetforindustrialenvironments,thesituationisdifferent.Inmostofthesecasesinformationaboutthechemicalcompositionofindoorairdoesnotallowustopredicthowtheairwillbeperceived,sincethecombinedeffectofthousandsofthesecontaminants,togetherwithtemperatureandhumidity,canproduceairthatisperceivedasirritating,foul,orstale—thatis,ofpoorquality.Thesituationiscomparabletowhathappenswiththedetailedcompositionofanitemoffoodanditstaste:chemicalanalysisisinadequatetopredictwhetherthefoodwilltastegoodorbad.Forthisreason,whenaventilationsystemanditsregularmaintenancearebeingplanned,anexhaustivechemicalanalysisofindoorairisrarelycalledfor.Anotherpointofviewisthatpeopleareconsideredtheonlysourcesofcontaminationinindoorair.Thiswouldcertainlybetrueifweweredealingwithbuildingmaterials,furnitureandventilationsystemsastheywereused50yearsago,whenbricks,woodandsteelpredominated....
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