Helps reduce white dust, a deposit of minerals caused by hard water. For best results, replace filter after every 30-40 fillings under normal use, or 1-2 months, or when the humidifier has not been operated for an extended period. To install, simply place the filter into the humidifier’s empty water tank right onto the small pin. Wait 15 minutes for the water to pass through the filter before re-starting the humidifier. Helps extending the life time of the humidifier. Fits all Crane Drop Cool Mist Humidifiers EE-5301 series.