Oxygen Icon An asphyxiant gas is a gas that reduces or displaces the normal oxygen concentration in breathing air. Exposure for prolonged periods of oxygen depleted air will lead to death by asphyxiation (suffocation). Because asphyxiant gases are relatively inert and odorless, their presence may not be noticed until the effects of elevated blood carbon dioxide (hypercapnia) are recognized by the body.

Examples of asphyxiant gases are nitrogen, argon, and helium. The Earth’s atmosphere is comprised of 79% of these gases (mainly nitrogen) and 21% oxygen. Normal ambient air contains an Oxygen concentration of 20.9% volume. When the Oxygen level dips below 19.5% v/v, the air is considered Oxygen-deficient. Oxygen concentrations below 16% volume are considered highly dangerous for humans.

Possible Causes of Oxygen Depletion

  • Chemical Reactions
  • Displacement
  • Combustion
  • Oxidation