Volcanic gas concentrations from the fumaroles on the north side of Mount Hood's Crater Rock are sampled on a regular basis. Yearly measurements from this location have occurred since 2008. After collection, the samples are taken back to the laboratory for an analysis of the gases' chemical composition. By routinely collecting gas samples and comparing their composition to past measurements, scientists can track the geochemical evolution of the volcanic system and become aware of any subtle changes that might indicate a rekindling of eruptive activity. Emission rates of several volcanic gases are also measured annually, either during on-site visits or with airborne monitoring systems. Although Mount Hood is not currently in a state of eruption, it remains an active volcano.