There's no wildfire. Why isn't Bay Area air quality better?

High clouds and fog hung over San Francisco on Nov. 15, 2021. A. Graff. There were no major wildfires burning in California, yet Air Quality ... MOSTPOPULAR Harris'ComedyCentralinterviewturnsawkwardthencontentious BayAreaweatherforecast:'Wearelookingataverywetpattern' Thisunhinged2002rom-comisSF’sanswerto‘SexandtheCity' BayAreawomansuesDisneylandfor‘deceptive’practices Planapprovedtodrop3,000poundsofrodenticideonFarallones Shouldyoucancelyourholidayplansbecauseofomicron? FavoriteSFbrunchspotclosesafternearly30years HighcloudsandfoghungoverSanFranciscoonNov.15,2021.A.Graff TherewerenomajorwildfiresburninginCalifornia,yetAirQualityIndexreadingsacrosstheSanFranciscoBayAreaonMondaymorningwereabove100onPurpleAir,thepopularwebsitethatprovidesliveairqualityreadings.  OnMondaymorning,theregionwasaseaoforangedots.Itwasthesamethingovertheweekend. TheBayAreaAirQualityManagementDistrict'sreadingsshowedabetterpicturewithairqualityintheBayAreamostlybelow100andintheyellow"moderate"range—butthisstillmayleaveresidentswonderingwhyairqualityisn'tbetterinwinter,especiallyafteraperiodofrain. AaronRichardson,aspokespersonforthemanagementdistrict,saidit'snotunusualforairqualitytodeteriorateinthewinter,NovemberthroughFebruary,duetosmokefromfireplaces.Therearesome1.4millionfireplacesacrosstheregion,districtdatashows. "Wehaveatemperatureinversionlayerovertheareawithhotairovercoolairandthatcreatesalidthattrapsthefireplacesmoke,"saidRichardson,notingthatinversionlayersareatypicalwinterweatherpatternintheBayArea. AnotherfactorimpactingconditionsovertheweekendandonMondaywereoffshorewindsblowingparticulatematterfromtheCentralValleytowardthecoast,worseningairqualityintheBayArea. "Thisistheseasonwhenwestarttoseesomebuildupoffineparticulatepollution,andwehavealittlemorethannormalbecauseoftheoffshoreflowcominginfromtheCentralValley,"Richardsonsaid. KrstineRoselius,anothermanagementdistrictspokesperson,saidthewindsarealsopushinginmoisture—andtheseconditionscanpushupreadingsonPurpleAirsensorsthatRoseliussaidaresensitivetohumidity.  "WehavefogfromtheCentralValleyandthehumiditycanthrowoffthePurpleAirsensors,"RoseliussaidMondaymorning."Rightnow,I'mlookingatPurpleAir,numbersinSanFranciscoandMarinareover100.Onoursite,SanFranciscois85.PurpleAirusesadifferenttechnology.Theyrunabout30%higher[thanthesensorsusedbythedistrict]." TopPicksInShopping Shopping WhattodoandwheretostayonaweekendtriptoSanDiego Shopping ThenewNintendoSwitchOLEDisinstockatWalmart Shopping 10ofthebestholidaygiftsunder$50 Shopping DysonSupersonicHairDryerreview:Yes,it'sworth$400 TheAirQualityIndex,orAQI,operatesonascalefrom0to500.ThehighertheAQIvalue,thegreaterthelevelofairpollutionandthegreaterthehealthconcern.AnAQIvalueof50orbelowrepresentsgoodairquality,whileanAQIvalueover300signalshazardousconditions.BothPurpleAirandtheairqualitydistrictusethisscale. TheairqualitydistrictpullsitsAQIreadingsfromhighlyaccuratesensorsmonitoredbytheEnvironmentalProtectionAgency. PurpleAirsensorsareinstalledbyeverydaypeopleandconnectedtothecompany'sapp,Roseliussaid. "Thesearepeoplewhobuytheseandputtheseintheiryards,"Roseliussaid."Ifyouputitinyourbackyardbyyourdryerventthathumiditywillthrowoffthesensor.Ifyou'rebarbecuinginyourbackyardoneday,thatwillthrowitoff." WhetheryoulookatPurpleAirortheairdistrict,theairqualityintheBayAreaisconcerningthoughRichardsonsaidit'snotsevereenoughtorequireanairqualityalertwarningofhealthhazards. Themoderateconditionsareexpectedforthenextfewdays,airdistrictforecasterssaid. TopPicksInShopping Shopping WhattodoandwheretostayonaweekendtriptoSanDiego Shopping ThenewNintendoSwitchOLEDisinstockatWalmart Shopping 10ofthebestholidaygiftsunder$50 Shopping DysonSupersonicHairDryerreview:Yes,it'sworth$400