Which filters does the Aprilaire 400m take?

Humidifier pad 45, Humidifier pad 4788.

Aprilaire 400m humidifier filters: 45

Humidifier pad

Wicks harden with minerals and soak up less water over time.

Shop the humidifier pad on Amazon Other models that use 45

Humidifier pad

Wicks harden with minerals and soak up less water over time.

Shop the humidifier pad on Amazon Other models that use 4788

1Humidifier pad45

Part numbers come from Aprilaire (source 1, source 2), checked November 6, 2026. Amazon buttons open a search for the part number; we may earn a commission.

Where the model number is

On a label on the base, often under the water tank.

Other Aprilaire humidifiers

350360400400a400K400KZ400MK400MKZ400MZ400Z