The Best Home Air Quality Monitor - The New York Times

The SAF Aranet 4 is one of the most accurate CO2 monitors available, and its measurements can act as an indicator of your indoor air quality. Weindependentlyrevieweverythingwerecommend.Whenyoubuythroughourlinks,wemayearnacommission.Learnmore›UpdatesWehaveaddedaCO2monitor,theSAFAranet4,asapick.ItcanhelpyouidentifyandmitigatehighlevelsofCO2thatcanbuildupinindoorspaces.Homeairqualitymonitorsarelimitedintheirabilities—aswellastheirreliability—soifyou’reconcernedabouttheairqualityinsideyourhome,thefirstthingwesuggestyoudoismeasurewhat’sintheairoutside,becauseoutdoorconditionsoftendetermineindoorconditions.There’snosimplerwaytodothatthantousetheEnvironmentalProtectionAgency’sAirNowmobileapp,availablefreeoniOSandAndroid.Searchablebyzipcodeorplacename,andpresentedonamap,AirNow’sairqualityreadingscomefromdirectmeasurementsbyhundredsofmonitorsaroundtheUS,offeringanairqualityforecastinadditiontoreal-timedata.WhattoknowHow’stheairtoday?Outdoorairqualitypredictsindoorairquality.Beforebuyingamonitor,tryanairqualityindex(AQI)app.ReliabilityissuesAnaccurate,reliableindoorairqualitymonitorwouldbegreat,butthemodelswe’veconsideredhaveflaws.ParticlecheckTotestaccuracy,wecomparedhomeairqualitymonitors’measurementsagainstdatagatheredfromapro-gradeparticlecounter.HowtofixitIfdata(orahunch)suggeststhatyouhavepoorairquality,improveitbycirculatingairthroughpurifiersorHVACfiltration. Thetypeofhome-focusedindoorair-monitoringdevicesweevaluatedforthisguideofferlessinformationbycomparison,astheytypicallymeasureonlythelocalairborneparticlelevelsandsometimesvolatileorganiccompounds—gaseslikethevaporsfrompaint,cleaners,andglue.Theyrarelymeasurecarbonmonoxideandradon,twopotentiallydeadlygases.Manysmokedetectorsalsodetectcarbonmonoxide;seeourguidetosmokealarmsformoreaboutthem.TheEPAhasaguidetoradon,includingstate-by-stateresourcesforknowingwhetheryourregionisatriskandhowtogetyourhometested.Andwhetheryouhavemeasuredprooforjustahunchthatyourindoorairqualityispoor,therearesimple,consistentlyeffectivewaystocleartheairasmuchaspossible:RunanairpurifierorupgradeyourHVACfilterstocapturefineairborneparticles,andopenyourwindowsonnicedaystoventanyvolatileorganiccompounds.For2022,wehaveaddedarecommendationforaCO2(carbondioxide)monitor.ResearchersattheUniversityofColoradoinBoulderfoundthatCO2levelscouldbeusedasaproxyforcoronavirusriskincrowdedpublicindoorspacesbecauseweexhalebothCO2and,ifwe’resick,virusesinthesamebreath.Andevenabsentthevirus,bothpublicspacesandhomescanaccumulatehighlevelsofCO2fromeverydayactivities—notjustbreathing,butfromusinggasstovesandwaterheaters.WecontactedaresearchertotalkaboutusingCO2monitorsforairqualitymeasurements,andtogetherwecameupwithaproductrecommendation,aswellassomeadviceonhowtointerpretandreacttoitsinformationwhenmonitoringCO2athome.OurpickAirNowAccurate,local,freeofchargeTheEPA’sfreeAirNowappiseasilysearchable,deliversairqualityreadingsinalmosteverycorneroftheUS,andletsyouknowinadvanceofupcomingairqualityproblems.BuyingOptionsBuyfromAppleAppStore(free)BuyfromGooglePlay(free)BuyfromAirNowWerecommendusingtheAirNowappasyourfirststepbecauseoutdoorconditionsusuallycauseanyindoorairqualityissuesyoumayexperience.AlthoughAirNowisn’ttheonlyappofitskind,wefoundinourresearchthatmanyotherairqualityappssimplyrepackagethedatathattheEPAstationsgather,oftenwithoutaddingmuchclarity,newinformation,orinterfaceimprovements.ComparedwithAirNow,someappsmakeithardertopinpointyourlocation,whereasothersusealesscompletenetworkofmonitoringstationstogatherthedata.AirNowoffersyouthesimplestwaytogettheinfoandinterpretwhatitmeans.And—unlikeotherappswetested—itdoesn’tbombardyouwithadsthewholetime.AdvertisementAlsogreatSAFAranet4ReliableCO2monitoringTheSAFAranet4isoneofthemostaccurateCO2monitorsavailable,anditsmeasurementscanactasanindicatorofyourindoorairquality.BuyingOptions$239*fromAmazon*Atthetimeofpublishing,thepricewas$250.Theconcentrationofcarbondioxide(CO2)inindoorspacesisusuallyhigherthaninnaturaloutdoorair,anditcanrisetolevelsthatimpaircognitivefunction.ThemainreasonsarethecombustionofnaturalgasandofsimplyexhalingCO2.Ifyou’dliketoknowhowmuchCO2isinyourhome’soroffice’sair,theAranet4isourpick.Itsmeasurementsareeasytoreadonscreen,asareitsalertswhenthelevelisgettingtoohigh.Itsappalsosendsalerts,workswithbothiOSandAndroid,andaddsseven-daytrendmonitoringtohelpyouidentifypatternsofhighCO2.And,helpingtooffsetthecost,thehigh-qualitysensorshouldlastforuptosevenyears.AlsogreatTemtopM10AirQualityMonitorSimpleandsolidThisdevicesitsonadeskortableandpresentsindoorairqualityreadingsofparticulates,butwe’reconcernedaboutitsVOCmeasuresanditslong-termdurability.BuyingOptions$90*fromAmazon*Atthetimeofpublishing,thepricewas$96.Weunderstandthatmanypeoplereadingthisguidereallydowanttotakeindoormeasurements,andforthatwesuggesttheTemtopM10AirQualityMonitor—withcaveats.Alotoftheairqualitymonitorswe’veconsideredovermorethantwoyearsofresearchforthisguidehavetoomanycrediblereportsoffaultysensorsandconnectivityproblemsforustostronglyrecommendthem.TheM10isdistinguishedbyitssimplicity,though,withabrightdisplayshowingparticulatemeasurements(thatweconfirmedtobeaccurate),atinysize,andalackofWi-Ficonnectivity(agoodthinginthiscase).It’salsoaffordableenoughforyoutokeepyourexpectationsrelativelylow—andthere’sgoodreasonforyoutoapproachitthatway.Aswithotherinexpensiveairqualitymonitors,itsVOCmeasurementisdubious,andsomebuyershavereportedthattheirM10arriveddamagedorfailedwithinafewweeks.EverythingwerecommendOurpickAirNowAccurate,local,freeofchargeTheEPA’sfreeAirNowappiseasilysearchable,deliversairqualityreadingsinalmosteverycorneroftheUS,andletsyouknowinadvanceofupcomingairqualityproblems.BuyingOptionsBuyfromAppleAppStore(free)BuyfromGooglePlay(free)BuyfromAirNowAlsogreatSAFAranet4ReliableCO2monitoringTheSAFAranet4isoneofthemostaccurateCO2monitorsavailable,anditsmeasurementscanactasanindicatorofyourindoorairquality.BuyingOptions$239*fromAmazon*Atthetimeofpublishing,thepricewas$250.AlsogreatTemtopM10AirQualityMonitorSimpleandsolidThisdevicesitsonadeskortableandpresentsindoorairqualityreadingsofparticulates,butwe’reconcernedaboutitsVOCmeasuresanditslong-termdurability.BuyingOptions$90*fromAmazon*Atthetimeofpublishing,thepricewas$96.WhyyoushouldtrustusWhoshouldgetthisHowwepickedandtestedProblemswithindoorairqualitymonitorsOurpick:AirNowAlsogreat:SAFAranet4CO2monitorAlsogreat:TemtopM10AirQualityMonitorThecompetitionWhyyoushouldtrustusTimHeffernanhasoverseenWirecutter’sairqualitycoveragesince2015,withthattimeperiodspanningfiveseparatetestsofairpurifiers.Inadditiontodirectlytestingairqualitymonitors,Timinterviewedrepresentativesfromfivemanufacturers—Airthings,Awair,Dylos,Kaiterra,andTemtop—togainabetterunderstandingofhowthedevicestaketheirmeasurementsandwhattheycanbeusedfor.WealsospoketoKathleenOwen,anairqualityresearchengineerandamemberofairquality–focusedcommitteesorganizedbytheAmericanSocietyofHeating,Refrigeration,andAir-ConditioningEngineers(ASHRAE).JohnHolecek,alabscientistandformerNOAAresearcherwhospecializesinaerosolandparticulatepollution,hasalsocontributedhisprofessionalexpertisetoourworkonairqualitydevicesandtoolssince2015.WhoshouldgetthisThenationwideimpactofsmokefromincreasinglyintensewildfireshasledtorecentspikesinpoorairquality(evenastheoverallUSairqualitytrendinrecentdecadesshowssignificantimprovement).Betweentheseworseningfiresandtheincreasedgeneralawarenessofairqualityinresponsetothepandemic,youmightthinktherewouldbeplentyofgreathomeairqualitymonitorstochoosefrom.Yetthatisn’tthecase.Inourresearch,we’vefoundthatmostmonitorsofthisclassaren’tthatgreat,withmanygivingunreliable(ifnotfalse)readings,especiallyofvolatileorganiccompounds(VOCs)suchaschemicalvaporsandformaldehyde.Somemonitorscanaccuratelymeasurefineparticulates,typicallyPM2.5(particulatematterof2.5micronsindiameter,whichcanpenetratethelungs).Butthenumberofcrediblecomplaintsaboutobviouslyfalsereadingsisalarming.Webelievethatanappisthebetterfirststopformostpeoplebecauseitcouldsaveyoufrombuyinganindoorairqualitymonitoryoumaynotreallyneed.Wearrivedatourpositionindependently,andweranitpastKathleenOwen,anexpertairqualityengineerandASHRAEcommitteemember.Sheagreedwithourassessment,shesaid,basedontheinaccuraciesandcostoftheanalyzersversusthebenefit.Whetheryouuseanapp,amonitor,ornothingatall,thethingsyoucandotoimproveyourhome’sairqualityaresimilar.Toaddressparticulatepollutantsfromoutdoors,suchassmoke,pollen,orexhaustonaheavilytraffickedroad,firstcloseyourwindowsanddoors,thenrunanairpurifierand/orinstallmedium-MERVHVACfiltersandrunthesystemfrequently.Ifyouroutdoorairqualityindex(AQI)readingisgoodandyou’reconcernedaboutflushingoutVOCsorparticulatesfromwithinyourhome,youmightventilatethespacebybrieflyopeningwindowsanddoorsasasupplementtoongoingfiltrationfrompurifiersorHVACfilters.Howeveryoumonitortheair,this’llfixitTheBestAirPurifierOurtestresultsandrecommendationsforthebestequipmenttoimproveyourairquality.HowwepickedandtestedWhenwedecidedtorecommendanappasthebestairqualitymonitorformostpeople,weestablishedafewsimplecriteria:Wewantedanappthathadaclear,easilysearchableinterface,thatdrewonalargenumberofwidelydistributedsensorstomakelocalizedreadingsmorelikelyforusersinallcornersoftheUS,thatdidn’thavealotofbellsandwhistles,andthat,ideally,didn’trequireasubscriptionorpurchaseforanad-freeversion.Manypublicagencies,includingtheEnvironmentalProtectionAgencyanditsstate-levelequivalents,takeairqualityreadings,andthedatatheygatherispublic.Infact,mostappsusethatdata,nottheirown,asitwouldbeprohibitivelyexpensiveforotherorganizationstosetupaprivatenationwidenetworkofairmonitors.Sowhatyougetonmostairqualityappsisjustauniquedesign,notdifferentormoreaccurateinformation.WethenspenttimeintheAppleAppStoreandtheGooglePlayStore,identifyingtheappswewouldbemostlikelytoconsiderfirstbasedonacombinationoftheauthorityoftheapp’sdatasources,theapp’spopularityamongusers,andourassessmentofthelikelihoodthattheappwouldbeupdatedregularlyandremainsatisfyingtouse.Weultimatelydownloadedfourapps—AirCare,Airly,AirNow,andIQAirAirVisual(iOS)(Android)—andspentseveralhours(acrossmultipledaysandlocations)usingthemoniOSandAndroiddevices,learningtheirquirksandcomparingtheirfeatures.ProblemswithindoorairqualitymonitorsWenevergaveuponouroriginalgoalofrecommendinganindoorairqualitymonitor,yetwhenrevisitingthisguideinautumn2021,wewerealarmedbythenumberofserious,crediblecomplaintsstatingthatour2019airqualitymonitorpicksdeliveredobviouslyinaccuratereadings,especiallyforvolatileorganiccompounds(VOCs).Wehadfoundthemtobereliableonparticulatereadingsinourtesting,butclearlysomethingwasgoingwrongoncethedeviceshadrunforawhileinmanypeople’shomes.ManyreviewswereadalsocomplainedofglitchyWi-Ficonnectionsandpoorcustomersupport.Whenwelookedbackatthecompetitorswehadoriginallytestedbutnotpicked,wefoundasimilarpatternofcomplaintsonsomeofthem.Andindiggingfurther,wediscoveredthattheEnvironmentalProtectionAgencyhasextensivelystudied(PDF)homeairqualitymonitors(partofaclassofmonitorsitreferstoaslow-costsensors)andfoundtheiraccuracyandlongevitywanting,withtheirVOCsensorslastingforjustsixmonthstoayearbeforestartingtofail.Allofthisledustoreviseourcriteriaandrecommendations.Fortheoriginalversionofthisguide,weinsistedthatallofourselectionsbecapableofmeasuringonespecificformofairpollution:particulatematterof2.5micronsorsmaller,betterknownsimplyasPM2.5.Andwefavoredthosethatalsomeasuredvolatileorganiccompounds,betterknownasVOCs(inpractice,gasesandodors).PM2.5isofspecialconcernbecausesuchparticlescandeeplypenetratethelungsandareknowntocausehealthproblems.VOCsincludeahugerangeofcompounds,themostwellknownofwhichisprobablyformaldehyde.Aprecursorchemicalusedinmanyglues,foams,plastics,andbuildingmaterialsfoundinhomes,formaldehydeisaknowncarcinogen.ButinlightofthepatternoffailingVOCsensorswe’vesinceobserved,wenolongertrustthosedevices.Wealsocametodoubtthevalueofsmartairqualitymonitors,whichtypicallyuseyourlocationtopullinlocalAQIreadingssuchasthosefromtheEPA.Manyapps,includingAirNow,dothesamewithoutcostingyouanything.Wedidnotlookat“personalairqualitymonitors,”anicheclassofdevicesthataredesignedtobecarriedonakeychainornecklacetomeasuretheairqualitywhereveryougo.Basedoncommonownercomplaints—badapps,connectivityissues,poorcustomerservice—andwhatwe’velearnedabouthomeairqualitymonitors,wedon’tthinktheseportabledevicesareworthconsidering.Besides,anAQIapponyourphonecantellyouaboutlocalconditions,andifyoukeepanN95respiratormaskonhandwhenyou’reout,itwillprotectyoufromparticulatepollutantslikesmokeanddustiftheirlevelsarehigh.Ourpick:AirNowPhoto:MichaelMurtaughOurpickAirNowAccurate,local,freeofchargeTheEPA’sfreeAirNowappiseasilysearchable,deliversairqualityreadingsinalmosteverycorneroftheUS,andletsyouknowinadvanceofupcomingairqualityproblems.BuyingOptionsBuyfromAppleAppStore(free)BuyfromGooglePlay(free)BuyfromAirNowOutdoorconditionsoftendetermineindoorairquality,andthefirsttoolwesuggestusingtomonitorairqualityinyourareaistheEnvironmentalProtectionAgency’sAirNowmobileapp.AvailableforfreeoniOSandAndroid,AirNowoffersthebestcombinationofusability,breadthofcoverage,andclarityofinformationamongalltheapps(anddedicatedhardwaremonitors)we’vetested.TheAirNowappmakesiteasyforyoutofindthecurrentairqualityindex(AQI)intheplaceyou’reinterestedin.Itcanuseyourownlocationtofindthenearestmonitorandreportthecurrentreadings.Youcanalsotypeinaplacenameorzipcodeifyouwanttoknowwhat’sgoingonsomewhereelse,oryoucanzoominonaUSmaptogetanideaoftheAQIinabroaderregion.(Forexample,asI’mwritingthis,IcanseethatalargeportionofCaliforniaisreportingterribleairqualityduetothefiresburninginSequoiaNationalPark.)Theotherappswetried—AirCare,Airly,andIQAirAirVisual(iOS)(Android)—arelessadept.AirCare,forexample,letsyousearchbyzipcode,butifthatlocationdoesn’thaveamonitor,theappdoesn’tsuggestthenearestonetoit,leavingyoutohuntaroundontheapp’srathersparsemaporguessatothernearbyzipcodesuntilyoufindareading.Airlydoesn’tseemtorecognizezipcodesatall,anditdoesn’tdifferentiateplacenamesbystate.(ItypedinMoorefield,wantingtoseewhattheconditionswereintheWestVirginiatownIspentsummersinasakid,andAirlyproducedalistoffive“Moorefield,UnitedStatesofAmerica”entriesformetopickthroughuntilIfoundthecorrectone.)AirVisualdoesn’tletyoudozipcodeorplace-namesearches,period.Tofindtheplaceyou’reinterestedin,youhavetogothroughatediousseriesofsteps,firstpickingyourregionoftheplanet,thenyourcountry,then(intheUS)yourstate—andthenyouhavetoscrollthroughallthecityandtownnamestofindyours.AlloftheseappsuseyourlocationtofindthenearestdirectorestimatedAQI,asAirNowdoes,butit’sfrustratingnottobeabletoquicklycheckontheairqualityelsewhere,suchasyoumightwanttodobeforeatrip,orifyou’reconcernedaboutfamilyorfriendswhoarefaraway.Amongtheappswetested,AirNowalsocollectsdatafromthewidestnetworkofmonitors.ItusesEPAandstateandmunicipalmonitoringstations(andoccasionallythoseusedatindustrialsites,suchasmines,whereairqualityisapressingconcern),anditoffersdirectAQIreadingsfrommultiplemonitorsineverystate.You’rerarelyveryfarfromoneunlessyou’rewelloutintothesparselypopulatedpartsofthecountry,andifyou’reinacity,you’relikelynotmorethanafewmilesfromthenearestmonitor.AirlyandIQAirAirVisualsimplytakeAirNow’sdataandrepackageitinclunkierapps.(IQAirAirVisualalsooccasionallygivesreadingsthatare“modelledusingsatellitedata.”)AirCare,incontrast,employsdatafromanetworkofinexpensivePurpleAirsensors,whichbusinessesandindividualsuseasanalternativetotheprofessional-grademonitorsthattheEPAandotheragenciesuse.It’sagreatconcept—theaimistohavesomanyPurpleAirsensorsinusethathighlylocalizedAQIwillbeavailableforalmosteverycorneroftheworld—andPurpleAirsensorsprovedquiteaccuratewhenCalifornia’sSouthCoastAirQualityManagementDistricttestedthemagainstprofessionalequipment(PDF).Butfornow,thenetworkisnowherenearasrobustasAirNow’s.AirlyandIQAirAirVisualsimplytakeAirNow’sdataandrepackageitinclunkierapps.Finally,AirNowmakesiteasierforyoutounderstandyourlocalAQIthantheotherappsdo.TheopeningscreenpresentsthecurrentAQIinyourarea.Thisnumber,between0(perfect)and500(hellish),iscalculatedbasedonreadingsoffivecategoriesofairpollutant:ozone,particlepollution(PM2.5andPM10,thenumbersbeingtheparticles’sizeinmicrons),carbonmonoxide,sulfurdioxide,andnitrogendioxide.Theappalsocolor-codestheAQIsoyoucantellataglanceifthere’sanythingtobeconcernedabout.Green,forAQIsbelow50,meanstheairisconsideredhealthy;yellow,from51to100,indicatesmoderatebutacceptablelevelsofpollution;andorange,red,andpurpleindicateincreasinglypoorandunhealthyairquality.Ifyou’dliketoknowmore,tappingtheDetailsiconopensawindowwherethemeasurementsarebrokendownbycategory.CurrentlyAirNowreportsonlytwocategories—particlepollutionandozone—butit’shelpfultoknowwhetheroneortheotherisespeciallyhigh.ThatwindowalsoofferssimpleadviceforhowtorespondtoyourlocalAQI,suggesting“Enjoyyouroutdooractivities”forgreenAQIs,forexample.Theotherappsalsouseacolor-codedAQIdisplaytoquicklyindicatethecurrentairquality,buttheyclutterupthescreenwithless-usefuldataandothervisualmaterial,suchashistoriccharts.AirCareandAirlyalsoserveadsintheirfreeversions,whereasAirNowisfreetodownloadandad-free.Alsogreat:SAFAranet4CO2monitorPhoto:ConnieParkAlsogreatSAFAranet4ReliableCO2monitoringTheSAFAranet4isoneofthemostaccurateCO2monitorsavailable,anditsmeasurementscanactasanindicatorofyourindoorairquality.BuyingOptions$239*fromAmazon*Atthetimeofpublishing,thepricewas$250.TheairinmosthomescontainsmoreCO2thanoutdoorairdoes—sometimesalotmore,especiallyinmodern,tightlysealedhouses.Theelevatedlevelsareprimarilytheresultofourownrespirationandofnatural-gasstovesandovens,andCO2canbuildupinenclosedspacestoconcentrationsthatimpaircognitivefunction.It’simportanttonotethataCO2monitordoesnotgiveacompletepictureofyourindoorairquality.AhomeorofficecouldhavelowCO2levelsbuthighparticulatelevels,forexample.ThefreeAirNowappcangiveyouasenseoflocalparticulatelevels.Andifyou’dliketosupplementthatinformationwithameasureofCO2inyourindoorair,theSAFAranet4CO2monitorisourpick.TheAranet4’snon-dispersiveinfrared(NDIR)sensorisconsideredthemostaccurateanddurabletypeoutsideoflaboratory-gradeequipment.ItsscreendisplaystheCO2readingandany“unhealthylevel”alertsclearly.Anditsapp—compatiblewithiOSandAndroid—canalsosendalertsandshowlongertrendsinyourCO2levels,helpingyoutakeproactivestepstokeeptheminthehealthyrange.(Thankfully,thesolutionisusuallydead-simple:Openafewwindowsandletfreshairinuntiltheleveldropstoagoodnumber,especiallyifyou’vegotalotofguestsorwhenyou’recookingwithnaturalgas.HEPAairpurifiersandHVACfiltersmakenodifferencebecausetheycaptureparticles,notgases.)InchoosingtheAranet4,wespokewithAlexHuffman,anatmosphericchemistattheUniversityofDenver.Duringthepandemic,hecoauthoredastudyonCO2anditsrelationtoriskofcoronavirustransmission,andsomeofhiscolleagueshavebeentestingCO2monitorsthatareaimedathomeowners.“There’snoquestionthatthereareconsumerCO2sensorsouttherethatsuck,whichisnottoosurprising,”hesaid.“You’veprobablyheardthatthefirstthingyouwanttodoislookforanNDIRsensor,non-dispersiveinfrared,andthat’sabsolutelytrue,but—andIdon’thaveasolutiontothisproblem—whatI’veheardfromcolleaguesisthatthereareincreasingnumbersofthesesensorsthatpurportorclaimtobeNDIRbutaren’t.They’rejuststraight-uplies.”TheAranet4usesagenuineNDIRsensor.Insidethedevice,infraredlightisdirectedthroughair-samplingtube.BecauseCO2moleculesabsorbaspecificinfraredwavelength,adetectoratthefarendofthetubesimplymeasureshowmuchofitgetseliminatedfromthelightsample,thusgivinganaccuratemeasureofhowmuchCO2isintheair.NDIRsensorsaredurable,too,withanexpectedlifespanofsevenyears,helpingoffsettheirrelativelyhighcost.AndtheAranet4alsomeasurestemperatureandrelativehumidity,addingabitmoreutility.CO2monitorssawasurgeinusein2021afterresearchersattheUniversityofColoradoBoulderdemonstratedthatCO2levelscouldbeusedasaproxyfortheamountofcoronavirus,andthereforetheriskoftransmission,inanindoorpublicspace.AndgrowingawarenessthathighCO2levelscanimpairbrainfunctionhasalsobeendrivinginterestintheuseofCO2monitorsrecently,tohelpensurethatcrowdedspaceslikeclassroomsandofficeshaveenoughventilation.ItmakessensethatCO2wouldbuildupinplaceswheremanypeoplecongregate.But—andImayjustbeshowingmyownnaivetéhere—ithadneveroccurredtomethatCO2couldbeaconcerninanuncrowdedhome.SoIdidn’texpecttolearnmuchwhenIsetuptheAranetinmyapartmentafewmonthsago.InfactIlearnedalot,andmyexperiencemayhelpyoudecidewhethertheAranetisworthyourinvestment.Isetituponahotsummerday—oneofthefewweatherconditionswhenmywifeandIkeepallthewindowsclosedandturnoffourapartment’sfresh-airventilation.Andwediscoveredthatouraircontainedalmost900parts-per-millionofCO2,morethantwicethatoffreshoutdoorair.Inthecourseofanhour,itroseabove1,000ppm,triggeringayellow“causeforconcern”alertfromtheAranet—solelytheresultofmybreathinginthesamelarge(25-by-30-foot)roomasthemonitor.Anotherday,Ibakedbreadinourgasoven,andinthecourseof45minutestheCO2levelrosefromahealthysub-500ppmtoover1,600,wellpasttheAranet’sred-alertlevelof1,400.Aquickstir-fryonourstove’spowerburnersentitfrom600to1,550.Justmakingmymorningsingle-servingpotofstovetopespresso,whichtakesabout7minutesonthesmallestburner,canraisetheCO2levelbyahundredpoints.Ontheotherhand,Ifoundthatbysimplykeepingoneofourtwofresh-airventsslightlyopenandasinglewindowcrackedbyaneighthofaninch,wecanmaintainahealthylevelofabout600ppm(ifthestoveorovenisn’ton);thetrickleoffreshairisenoughtokeeptheCO2undercontrol.AndwhenI’mcookingorbaking,fullyopeningonewindowandtheventsfor20minutesdropstheindoorCO2levelclosetothatofthefreshairoutside,whichiscurrentlyhoveringaround400partspermillionhereinQueens.(Theglobalaverageis420,butregionalCO2levelsvaryformanyreasons.Weliveinaparticularlyleafy—byNewYorkCitystandards—neighborhood,andwithallthetreesintheirfullsummergreenery,CO2-absorbingphotosynthesisisprobablyhelpingknockourlevelsdownslightly.)Inshort:TheAranetsurprisedmebyrevealingjusthowquickly,andhowhigh,theCO2levelinahomecanriseasaresultofroutinedailybehaviors.Butalmostasquickly,Ilearnedsimplecounter-behaviorsthatkeepourhome’sCO2levelhealthywithoutmyneedingtoconstantlymonitorit.So,aswiththeotherairqualitymonitorswe’veconsidered,youdon’tstrictlyneedaCO2monitorifyou’rewillingtotakebasicstepslikeregularlyopeningyourwindowsorotherwisebringingfreshoutdoorairintoyourspace.Fortherecord,I’minthiscamp.Butifyou’dliketobeabsolutelycertainthatyourair’sCO2levelsarehealthy(and,ifthey’renot,thatyourremedialstepsreallyarebringingthelevelsdown),theAranet4isanaccurate,reliable,andreassuringdevice.Alsogreat:TemtopM10AirQualityMonitorPhoto:MichaelMurtaughAlsogreatTemtopM10AirQualityMonitorSimpleandsolidThisdevicesitsonadeskortableandpresentsindoorairqualityreadingsofparticulates,butwe’reconcernedaboutitsVOCmeasuresanditslong-termdurability.BuyingOptions$90*fromAmazon*Atthetimeofpublishing,thepricewas$96.Ifyoureallywantanindoorairqualitymonitor,wecautiouslyrecommendtheTemtopM10AirQualityMonitorfornowandwillsoontestaasimilarmodel,theP10AirQualityMonitor,thelatestversionofwhichclaimstohaveasuperiorPM2.5sensorandimprovedsoftware.TheM10measuresPM2.5,VOC,andformaldehyde(HCHO)tocalculateanairqualityindex(AQI).Itsbrightdisplayisreadablefromacrossaroom,anditstinysizeandsimpleformallowittofitnicelyonadeskorbedsidetable.Welikeitssimple,intuitiveinterface,too:Asinglebuttonturnsthedeviceon,andadditionalpressescycleyouthroughthereadings.LackingWi-Ficonnectivity,theM10hasnoassociatedapp,letalonesmartfunctionality.Butformanypeople,thatworksjustfine.InourtestoftheM10’sPM2.5sensor,itgavealmosttheexactsamereadingsasothermonitorswetested,andittrackedwiththereadingswegotfromtheprofessional-gradeparticlecounterthatweusedasacontrol.ThisconsistencygaveusconfidenceintheM10’saccuracyonPM2.5.TheM10alsorespondedinstantlywithhighernumberswhenweintroducedaVOC(intheformofamistofrubbingalcohol),indicatingthattheVOCsensorwasworkingasitshould.Wedidnottestitsformaldehydesensor.WithnoWi-Ficonnectivityandnoapp,theM10doesn’ttrackitsreadingsovertime,itdoesn’tofferoutdoorairqualitydatafromnearbyweatherstations,itdoesn’tgiveyousuggestionsforhowtoimproveyourairquality,and,ofcourse,itdoesn’tletyoucheckyourairqualityonyourphone.Ifthatsoundslikeblessedsimplicity,you’llprobablylikeit.Allthatsaid,wehavesomefairlystrongreservations.AlthoughtheM10getsmanypositive,detailedreviewsfromownerswhohavefoundtheirunitstobereliableandaccurate,sincelate2020ithasreceivedaspateofone-starreviewsfrompeoplewhoseunitsarrivedbrokenordefective,andTemtop’scustomerservicehasnotbeenresponsive.(Manyofthepositivereviewsarefromthissameperiod,too,soit’snotanacross-the-boardproblem,butitisarisktoweighwhenyou’redecidingwhethertobuyone.)And,asweexplaininHowwepickedandtested,VOCsensorsinlow-costairqualitymonitorsareknowntohaveshortworkinglives—sixmonthstoayear,theEPAsays—sowedoubttheirvalue.Forissuesthatarise,Temtopoffersa45-dayreturnperiodandalimitedone-yearwarranty.WhenyoupresstheM10’ssinglebutton,thedevicecyclesthroughitsfourscreens,displayingPM2.5,VOCs,formaldehyde(HCHO),andairqualityindex.Video:MichaelMurtaughThecompetitionTheKaiterraLaserEgg+Chemical,ourformertoppickamonghomeairqualitymonitors,hassufferedfromstockissuesand,sincewerevieweditin2019,hasbeenhitbywavesofcomplaintsaboutfailedVOCsensors,abandonedsmartfeatures,andpoorcustomerservice.Wenolongerrecommendit.TheTemtopM10iWiFiAirQualityMonitorisfunctionallyidenticaltotheM10butaddsWi-Ficonnectivity(butonlyon2.4GHznetworks)andasimpleappthatdisplaysthedevice’sreadings,tracksthemovertime,andletsyouturnthedeviceonandoff.Ifyouwantthosefeatures,youhavetopayabout$40to$80moreforthismodeloverthebasicM10.In2019wetestedtheAwair2ndEdition,whichAwairhassincereplacedwiththesimilarAwairElement.Botharebeautiful-lookingdevices,butinourtests,wefoundthe2ndEditionfrustratingtouseduetopoorconnectivity,anunclearuserinterface,app-reliabilityissues,andotherproblemsechoedinownerreviewsoftheElement.TheIQAirAirVisualPromonitoreasilyconnectedtoourWi-Finetwork.Itsappisclearlylaidout,andboththedeviceandtheappoffersimple,practicaladviceonhowtoaddressindoorairqualityissues(forexample,theysuggestopeningawindowiftheoutdoorairqualityisgood).Butthedevice’sphysicalinterfaceisaclunky,frustratingexperience,andatthiswritingthemachineissimplyfartooexpensive:For$270,youshouldgetmorethanjustPM2.5andCO2measurements(plushumidityandtemperature,whicharen’tstrictlyairqualitymeasurements).TheDylosDC1100isasimple,accurateparticlecounterthatmeasuresdownto1micron—alltheotherdeviceswetestedgotoonly2.5microns(PM2.5).Butit’saspecialist’sdevice,generatingreamsofdatabutleavingtheanalysisuptotheuser.Forthesmallsubsetofpeoplewhowantrawdataaboveanythingelse,theDC1100maybeattractive.Formostpeople,however,ourpicks’simplerdisplaysandeasy-to-digestalertsaremuchmoreuseful.TheIgeressIndoorAirQualityMonitorisoneofanumberofsimilar,relativelyinexpensivemonitorsthatweencounteredinoursearch.Wetesteditbecauseitisreasonablypopular,butitdeliveredwildlydifferentreadingsfromalltheothermonitorswetried,leadingustodoubtitsaccuracy.TheTemtopLKC-1000S+AirQualityMonitor(andthesimilar,lessfull-featuredLKC-1000SandLKC-1000E)arehandheldmonitors.The1000S+wasaccurateandeasytosetupandoperateinourtests.Butaftertestingbothhandheldanddesktopmonitors,westronglybelievethatofthetwotypes,desktopmonitorsarethebetterchoiceformosthomes.They’resmaller,they’redesignedtofitintoanyhome’sdecor,andtheydon’tlooklikeaStarTrekprop.ThePlumeLabsFlow2,liketheAtmotubePro,isapersonalairqualitymonitor,andwedidnottestsuchmodelsforthisguide.Airthingsisawell-regardedmanufacturerofairqualitymonitors,specializinginradondetection.Whenwetestedmonitorsin2019,noneofthecompany’smanydevicesmeasuredparticulates,arequirementforinclusioninourtests.AnewdevicethatmeasuresPM2.5,theViewPlus,isavailable,butwehavenottestedit.TheEveRoomdoesnotmeasureparticulates,arequirementforourtesting.AboutyourguideTimHeffernanTimHeffernanisaseniorstaffwriteratWirecutterandaformerwriter-editorforTheAtlantic,Esquire,andothers.Hehasanchoredourunequaledcoverageofairpurifiersandwaterfilterssince2015.In2018,heestablishedWirecutter’songoingcollaborationwithTheNewYorkTimes’sSmarterLiving.Whenhe’snothere,he’sonhisbike.FurtherreadingTheBestAirPurifierbyTimHeffernanOurtestresultsandrecommendationsforthebestequipmenttoimproveyourairquality.HowtoGetBetterIndoorAirQualitybyHarrySawyersUsetheseitemstocleanyourhome’sair,reducethesourcesofrespiratoryproblems,andlimittheinfiltrationofnewparticulates.HowtoDIYanAirPurifierbyTimHeffernanIfyourairqualityisbadandyoudon’thaveanairpurifier,anHVACfiltertapedtoaboxfanisbetterthannothing.Wirecutter’s100MostPopularPicksof2021byWirecutterStaffTheseusefulthingswerethemost-purchasedWirecutterpicksin2021.EditDismiss