Nitrogen

Excerpted from the 2000 Report of the AVMA Panel on Euthanasia –

"Nitrogen (N₂) and argon (Ar) are colorless, odorless gases that are inert, nonflammable, and nonexplosive. Nitrogen comprises 78% of atmospheric air, whereas Ar comprises less than 1%. Euthanasia is induced by placing the animal in a closed container that has been prefilled with N₂ or Ar into which the gas is then rapidly introduced. Nitrogen/Ar displaces O₂, thus inducing death by hypoxemia.

"Nitrogen and [argon] can be distressful to some species (eg, rats).

"Loss of consciousness is preceded by hypoxemia and ventilatory stimulation, which may be distressing to the animal.

"Therefore, this technique is conditionally acceptable only if O₂ concentrations < 2% are achieved rapidly, and animals are heavily sedated or anesthetized. With heavy sedation or anesthesia, it should be recognized that death may be delayed. Although N₂ and Ar are effective, other methods of euthanasia are preferable."