Inert gas asphyxiation are more uncomfortable in low-oxygen environments that result from inert gas exposure; however, the experience is still less aversive than CO exposure. A typical human breathes between 12 and 20 times per minute at a rate primarily influenced by carbon dioxide concentration, and thus pH, in the blood. With each breath, a volume of about 0.6 litres is exchanged from an active lung volume (tidal volume + functional residual capacity) of about 3 litres. Normal Earth atmosphere is about 78% nitrogen, 21% oxygen, and 1% argon, carbon dioxide, and other gases. After just two or three breaths of nitrogen, the
Atmosphere of Venus The densest part of the atmosphere, the troposphere, begins at the surface and extends upwards to 65 km. At the furnace-like surface the winds are slow, but at the top of the troposphere the temperature and pressure reaches Earth-like levels and clouds pick up speed to 100 m/s. The atmospheric pressure at the surface of Venus is about 92 times that of the Earth, similar to the pressure found below the surface of the ocean. The atmosphere has a mass of 4.8 kg, about 93 times the mass of the Earth's total atmosphere. The density of the air at the