Question

Why do mountaineers carry oxygen cylinders with them?

Answer 1

Hint: Atmospheric pressure decreases with increase in altitude. At high altitudes, the oxygen partial pressure drops below a level that can sustain life. The amount of oxygen in air is \[21\% \]. At high altitudes the fraction of oxygen does not change, but the total exerted pressure is reduced and also the partial pressure of oxygen. The partial pressure of oxygen at \[16\] is usually considered life sustaining.

Complete explanation:
With increase in altitude the barometric pressure drops which causes the air to thin. This also decreases the concentration of oxygen in the atmosphere. It is difficult to breathe at high altitudes since there is only less oxygen available.
Humans need oxygen to survive and function optimally. When there is no optimum amount of oxygen available to the body, the physical and cognitive abilities get adversely affected. The body mass and the immune system also get negatively affected. So, mountaineers usually carry oxygen cylinders when climbing at high altitudes.
The oxygen cylinder usually contains \[63\% \] oxygen rather than the \[21\% \] oxygen in normal atmospheric air. Since the barometric pressure at high altitudes is one third of the pressure at sea level, to obtain the same amount of oxygen with each breath, a mountaineer needs to inhale three times the oxygen per litre of air. This is why \[63\% \] oxygen is used.

Note:
At high altitudes mountaineers may experience health problems such as acute mountain sickness, nose bleed, dry skin etc. The area eight thousand meters above sea level is called the death zone. The air is so thin here that only \[30\% \] of the oxygen at sea level is available. Most people black out and die after being at this altitude for a few minutes. Hence people use oxygen enriched cylinders when climbing above eight thousand meters. Travelling without an oxygen cylinder is dangerous and definitely not recommended.