I left the humidifier/steamer going for 24 hours the first week and changed the vicks every 8 hours. Mine takes six hours to run out of water and shuts itself off if the water level goes down too low. Toby was very congested when I started, and this cleared up after the second day. He also stopped coughing after the second day, and only had the sniffles. Since hubby and I were both fighting colds, it also helped us
