Water is the most important component in the volcano's fumarolic gases, comprising 96.05% to 97.95% by volume. Examinations of deuterium and oxygen-18 content of the water have determined that like the water of fumaroles in other Andean volcanic centres, Irruputuncu water is a mixture of weather-related water and water contained in andesite. The helium isotope ratios indicate the magmatic component dominates the gasses at Irruputuncu, Much of the carbon dioxide comes from subducted and crustal carbonates. The gases escape from oxidizing magma at and pass through a weakly developed hydrothermal system with temperatures of c. . Argon isotope ratios appear to be radiogenic.