Notable examples of asphyxiant gases are methane, nitrogen, argon, helium, butane and propane. Like all hydrocarbons, ethylene is an asphyxiant and combustible. Like any gas besides oxygen, argon is an asphyxiant. Many inhalants act primarily as asphyxiant gases, with their primary effect due to oxygen deprivation. Methane is an asphyxiant gas which can reduce the normal oxygen concentration in breathing air. Carbon dioxide is an asphyxiant and can be a freezing hazard if vented improperly. Krypton is considered to be a non-toxic asphyxiant. Methane, an asphyxiant, is a chemical compound that is the main component of natural gas. Asphyxiant gases in the breathing air are normally not hazardous.