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 Pluto is about (), roughly 100,000 times less than Earth's atmospheric pressure. The temperature on the surface is , but it quickly grows with altitude due to methane-generated greenhouse effect. Near the altitude it reaches , and then slowly decreases. Pluto is the only trans-Neptunian object with a known atmosphere. Its closest analog is the atmosphere of Triton, although in some aspects it resembles even the atmosphere of Mars. The atmosphere of Pluto has been studied since the 1980s by way of earth-based observation of occultations of stars by Pluto and spectroscopy. In 2015, it was studied from a close distance