Humidifier bottle. If you utilize just one, clean it every three times with warm water and mild dish soap. Rinse it with very hot water. You can also soak it in a mix of vinegar and water for a couple of minutes to filter any leftover germs. Dry the bottle https://allhealthmarket.com/product/medical-supplies/portable-oxygen-concentrator-generator/oxygen-concentrator-machine-camping-use-oxygenator-driving-oxygen-bar-with-24-hours-battery-lasting-oxygen/