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
Modified atmosphere demand. Atmosphere within the package can be modified passively or actively. In passive modified atmosphere packaging (MAP), the high concentration of CO and low O levels in the package is achieved over time as a result of respiration of the product and gas transmission rates of the packaging film. This method is commonly used for fresh respiring fruits and vegetables. Reducing O and increasing CO slows down respiration rate, conserves stored energy, and therefore extended shelf life. On the other hand, active MA involves the use of active systems such as O and CO scavengers or emitters, moisture absorbers, ethylene