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-operated reloading piston has traveled a short distance. Most systems, however, vent excess gas into the atmosphere through slots, holes, or ports. A gas trap system involves 'trapping' combustion gas as it leaves the muzzle. This gas impinges on a surface that converts the energy to motion that, in turn cycles the action of the firearm. Hiram Maxim patented a muzzle-cup system in 1884 described in though it is unknown if this firearm was ever prototyped. John Browning used gas trapped at the muzzle to operate a 'flapper' in the earliest prototype gas-operated firearm described in . The Danish Bang rifle used