Lobb Replacement Humidifier Pad – # 2211096 5″ drum-type replacement humidifier pad for Lobb WA-2, WA 1700 furnace mount humidifiers. Lobb Part Number 224 The foam, belt-style humidifier filter is also known as the water pad, or evaporator pad. It is the “heart” of your drum style whole-house humidifier and the one humidifier part that needs regular replacement. Inside the humidifier, a rotating evaporator pad lifts water from the water pan into the air stream. The filter is constructed of a foam material that absorbs and holds water for evaporation. Features: Value-priced alternative to factory original parts Made in the USA of quality materials Provides humidity to keep you comfortable during the dry heating season Guaranteed to fit your whole house humidifier