Excessive use of hard water will degrade filters and cause them to turn yellow prematurely. Also compatible with Honeywell humidifiers HEV-300 Series : HEV-312, HEV-355, HCM-700 Series: HCM-710, HCM-1000 Series：HCM-1000, HCM-1000C, HCM-1010 Enviracaire Series：ECM-250, HCM-2000 Series: HCM-2000C, HCM-2001, HCM-2002, HCM-2020, HCM-2050, HCM-2051, HCM-2052, Compare to humidifiers Filter A, HAC-504,HAC-504AW,HAC504V1.
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