We live in a mixture of gases that we call air (hau takiwā). Our atmosphere (kōhauhau) is the layer of air that surrounds Earth. Almost all (99%) of this mixture consists of two gases: nitrogen (78%) and oxygen (21%). The remaining 1% includes argon (0.9%), carbon dioxide (0.03%) and variable amounts of water vapour, traces of hydrogen, ozone, carbon monoxide, helium, neon, krypton and xenon. Although the air becomes less dense as you go up in the atmosphere, the proportions of gases in the mixture remain the same, regardless of how dense the air is.