Humidifying floor vent filters Easily add moisture to the air with this specially designed floor vent. Simply replace some of your existing floor vents with the humidifying vent, insert the special wicking filter, and add water. As your furnace cycles add through the vents, the air will pick up moisture to sooth dry skin and nasal passages and eliminates static electricity. Fits 4" x 10" and 4" x 12" floor vents. Made in the USA. Plastic. 2 pack replacement filters $6.98 Read our blog on some more energy saving tips.