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Standard sea-level conditions (SSL), [1] also known as sea-level standard (SLS), defines a set of atmospheric conditions for physical calculations. The term "standard sea level" is used to indicate that values of properties are to be taken to be the same as those standard at sea level, and is done to define values for use in general calculations.
At 40,000 ft (12,192 m), the ambient air pressure falls to about 0.2 bar, at which maintaining a minimum partial pressure of oxygen of 0.2 bar requires breathing 100% oxygen using an oxygen mask. Emergency oxygen supply masks in the passenger compartment of airliners do not need to be pressure-demand masks because most flights stay below 40,000 ...
Pressure as a function of the height above the sea level. The human body can perform best at sea level, [7] where the atmospheric pressure is 101,325 Pa or 1013.25 millibars (or 1 atm, by definition). The concentration of oxygen (O 2) in sea-level air is 20.9%, so the partial pressure of O 2 (pO 2) is 21.136 kilopascals (158.
Exhaled air at sea level contains roughly 13.5% to 16% oxygen. [ 2 ] The situation is even more wasteful of oxygen when the oxygen fraction of the breathing gas is higher, and in underwater diving, the compression of breathing gas due to depth makes the recirculation of exhaled gas even more desirable, as an even larger proportion of open ...
Breathing pure oxygen results in an elevated partial pressure of oxygen in the blood: a climber breathing pure oxygen at the summit of Mt. Everest has a greater arterial oxygen partial pressure than breathing air at sea level. This results in being able to exert greater physical effort at altitude.
The chamber is pressurised with air to 3.7 bars (370 kPa; 54 psi). The subject in the centre is breathing 100% oxygen from a mask. Although oxygen is essential to life, in concentrations greater than normal it becomes toxic, overcoming the body's natural defences (antioxidants), and causing cell death in any part of the body.
One of the more frequently used treatment schedules is the US Navy Table 6, which provides hyperbaric oxygen therapy with a maximum pressure equivalent to 60 feet (18 m) of seawater (2.8 bar P O 2) for a total time under pressure of 288 minutes, of which 240 minutes are on oxygen and the balance are air breaks to minimise the possibility of ...
Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Earth's early atmosphere consisted of accreted gases from the solar nebula , but the atmosphere changed significantly over time, affected by many factors such as volcanism , impact events , weathering and the evolution of ...