These species a measured at a number of global monitoring stations, which operate under the authority of international programs such as the Advanced Global Atmospheric Gases Experiment(AGAGE) project, the World Meteorological organization's Global Atmospheric Watch program, and various other national programs. A number of manned/semiautonomous stations make measurements of these gases in situ, and flask samples are also collected at other stations and returned to base laboratories for periodic analysis an approach only possible for the nonreactive, long-lived species under consideration.