LittleHippo WISPI Humidifier Replacement Demineralization Filters (3-Pack) 3 REPLACEMENT DEMINERALIZATION FILTERS - Use a demineralization filter to reduce the amount of "white dust" emitted from your WISPI humidifier if your tap water has a high mineral content! ? DESIGNED FOR USE WITH WISPI - Specially designed for use with LittleHippo's WISPI children's humidifier, diffuser and night light ? HOW TO USE THE DEMINERALIZATION FILTER - Before the first use, soak the filter for 30 minutes in cool water. Place one demineralization filter inside WISPI's base, with the outer slits facing downward. ? WHEN TO REPLACE THE FILTER - We recommend changing the filter after 250-300 hours of normal use or if WISPI has not been used for an extended period of time. ? Little Hippo stands behind its products. If you are not happy, contact our customer support team!