It is at sea level. The higher you climb from sea level, to reach the summit of Mount Everest (for example), the less oxygen is in the very thin air. This is why the majority of climbers of Mount Everest have to carry oxygen cylinders. Someone occasionally achieves the summit without oxygen tanks! Therefore, the higher the altitude, the thinner the oxygen in the air.
"air" and/or "oxygen"
Air Pressure.
No. It changes negligably from the standard ~21% regardless of elevation. (at any elevation you can survive at anyway) :p The actual amount of available oxygen does change, due to a decrease in atmospheric density as elevation increases. For example: at 17,700ft (apparently a common Mt. Everest base camp) the air density is approximately 51% of the density at sea level. So you COULD express it as 51% of ~21%, which would be about 10.71%.
In the troposphere, the temperature drops. In the stratosphere (layer above the troposphere) it increases with elevation. In the mesosphere, temperature drops again with elevation. In the theromosphere, it goes up again (to nearly stellar surface temperatures).
The oxygen content of air is approximately 21%. Nitrogen is the largest component of air as it takes up 78% of the atmosphere.
"air" and/or "oxygen"
If your elevation increases, not only does oxygen decrease but all gasses decrease. The greater distance you are from the earth's surface you are, the less air there is. When there is less air, there is less oxygen. No other gas increases to make up for the loss of oxygen.
The amount of dissolved oxygen decreases when water temperature increases. Warm water is unable to dissolve as much oxygen gas.
The following changes are average changes, which means there might be exceptions more or less as we rise upward. But in general as elevation increases, on average: Temperature decreases Atm pressure decreases Wind velocity increases Gamma radiation increases Overhead turns black More and more stars are seen Shape of the planet as a sphere becomes obvious
No. It is a negative correlation which means, as the elevation increases the air pressure decreases.
Venous reserve is available to maintain tissue oxygenation if either systemic oxygen demand increases or arterial content falls.
Temperature decreases as the elevation increases.
Air Pressure.
As a general rule in the atmosphere, the higher the elevation the lower the temperature. However, certain atmospheric conditions may produce an 'inversion', where temperature increases with elevation.
Yes. As elevation increases, combustion is more difficult to sustain, since each unit volume of gas contains less oxygen. Just like it is difficult for us to breathe at high altitude, so it is for a fire.
As silica content increases viscosity increases.
No. It changes negligably from the standard ~21% regardless of elevation. (at any elevation you can survive at anyway) :p The actual amount of available oxygen does change, due to a decrease in atmospheric density as elevation increases. For example: at 17,700ft (apparently a common Mt. Everest base camp) the air density is approximately 51% of the density at sea level. So you COULD express it as 51% of ~21%, which would be about 10.71%.