Methane is important for electrical generation by burning it as a fuel in a gas turbine or steam generator.Methane is created near the Earth's surface, primarily by microorganisms by the process of methanogenesis. It is carried into the stratosphere by rising air in the tropics. Uncontrolled build-up of methane in the atmosphere is naturally checked although human influence can upset this natural regulation by methane's reaction with hydroxyl radicals formed from singlet oxygen atoms and with water vapor.Methane also affects the degradation of the ozone layer.Methane is not toxic, yet it is extremely flammable and may form mixtures with air. Methane is also an asphyxiant and may displace oxygen in an enclosed space.