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
Shale gas in the United States thickness of the Barnett varies from 100 to , but most economic wells are located where the shale is between 300 and thick. The success of the Barnett has spurred exploration of other deep shales. In 2007, the Barnett shale (Newark East) gas field produced of gas, making it the second-largest source of natural gas in the United States. The Barnett shale currently produces more than 6% of US natural gas production. In April 2015, Baker Hughes reports that there are 0 rig currently in activity at the Barnett gas field. (That doesn't mean 0 production as there are still