"Carbon dioxide" is the hot water which carbon dioxide (carbon dioxide) melted and is also known as the bath of Ramune.

In the hot spring law of Japan, it is defined as a carbonated spring with a carbon dioxide of 0.25 g or more (250 ppm) dissolved in 1 liter of hot water. It is said that the higher the concentration, the higher the concentration of the charcoal fountain. It is medically proven that the charcoal fountain has the unique and clear action which does not exist in other hot springs, and it is widely used in each direction.