Scientists study the hydrothermal system at Mount Rainier to learn about volcanic gas emissions at the volcano. The hydrothermal system is made up of hot, mineral-laden waters within the volcano that feed fumaroles and hot springs at its surface. Gas samples collected from fumaroles at Mount Rainier's summit in 1982 consisted of air enriched with carbon dioxide; no sulfurous gases were detected. However, sulfurous gases have been reported previously from summit fumaroles. When present, volcanic gases are a significant hazard only to climbers who enter the summit ice caves. When the volcano reawakens, however, the gas-emission rate will increase, as will the potential hazard from volcanic gases.