Inert gas asphyxiation lacks oxygen and consists of an asphyxiant gas (one or more of argon, nitrogen or carbon dioxide), causing the animals to lose consciousness. Argon and nitrogen are important components of a gassing process which seem to cause no pain, and for this reason many consider some types of controlled atmosphere killing more humane than other methods of killing. However, "stunning" is often done using carbon dioxide. If carbon dioxide is used, controlled atmosphere killing is not the same as inert gas asphyxia, because carbon dioxide at high concentrations (above 5%) is not biologically inert, but rather is toxic and also
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