Atmosphere of Earth the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around . Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earth's atmosphere and its processes is called atmospheric science (aerology). Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of Earth's atmosphere are nitrogen, oxygen, and argon. Water vapor accounts for roughly 0.25% of the atmosphere by mass. The concentration of water vapor (a greenhouse gas) varies significantly from around
Gas venting or controlled combustion of gases from coal mining and of so-called biogases. In practice, it is impossible or impractical to capture and filter the air from coal mining (esp open-cast) and to completely degas hydrocarbon product and/or water produced from the ground which in some cases may be disposed at surface for and used after treatment. Melting of methane hydrates in the world's oceans or sea ice would also constitute uncontrolled gas leakage to atmosphere. Gas venting Gas venting is the intentional safe release, without combustion, into the earth's atmosphere of gases that cannot be readily recycled into a production