Many first-time air humidifier buyers are unsure when they hear the gurgling sound emanating from their brand-new machine. The good news is, that noise means the humidifier is working properly. That is the sound of water in the machine being drawn where it needs to go in order to properly humidify the home. When it comes to the water in your humidifier, you should also know that most manufacturers recommend using clean water only in the machine. Adding medicine to the water reservoir is not a good idea as you may damage the humidifier with residues or other by-products. Some humidifiers come with a "medicine cup" type compartment that is intended for menthol-type inhalants or other medicinal products.