Since the air pressure at altitude is less than at sea level, the air there is less dense, rarefied. With each breath in your lungs, there is less oxygen, namely its molecules, than when breathing in a lowland, closer to sea level. At the same time, the oxygen content (its percentage) in the air does not change.

This means that in such conditions it is more difficult for the human body to absorb the amount of oxygen it needs than when it is at sea level. When the body's need for oxygen exceeds the ability to absorb it from rarefied air (this can happen with significant physical exertion), hypoxia develops - oxygen deficiency. The reason for the appearance of hypoxia even before the start of the descent from the mountain is often the heavy physical exertion that the rider experiences during the ascent. Signs and symptoms of hypoxia include fatigue, dizziness, weakness, and total loss of energy. It seems to you that the work you are doing is much more difficult than usual.

Fortunately, hypoxia is easy to avoid. Being high above sea level, you need to limit your physical activity and rest more often. Take extra time to pack, don't take more than you need, and remember that in the mountains, every kilogram costs three. Make sure you don't get short of breath. If you live high above sea level, or spend a lot of time in the mountains, then your body, accustomed to rarefied air, is less susceptible to hypoxia.

The state of hypoxia can come unexpectedly, in the final phase of your physical exercises. In the lowlands, your body is affected by atmospheric pressure to a greater extent than in the mountains, and your body easily receives the oxygen it needs. In the mountains, in a rarefied atmosphere, after heavy physical exertion, it is difficult to restore your breathing.

Feeling signs of hypoxia, immediately stop making any physical effort, take a break and restore breathing. Resume activity only after breathing returns to normal, and do everything at a slower pace. If you are a little tired doing physical exercises, rest and restore your breath before the next uphill.

The intensity of the development of mountain sickness depending on the height:

1000-2500 Physically untrained people experience some lethargy, slight dizziness, palpitations. But there are no symptoms of altitude sickness yet.

2500-3000 Most physically healthy people will already feel the effect of altitude and rarefied air. There will be a headache, pain in muscles and joints is possible, loss of appetite, respiratory rhythm disturbances, drowsiness are possible. But there will most likely not be pronounced symptoms of mountain sickness. But some untrained or weakened people may experience deviations in behavior. High spirits, excessive gesticulation and talkativeness, causeless fun and laughter. Very similar to a little alcohol intoxication.

4000-5000 Maybe she will show up here. Mountain sickness. In its most unpleasant symptoms. Acute and severe mountain sickness in some cases may occur. A sharp deterioration in breathing, a violation of the rhythm of respiratory movements, complaints of suffocation. Frequent nausea and vomiting, pain in the abdomen. The excited state is replaced by apathy, indifference, low mood, melancholy. Pronounced symptoms of altitude sickness may not appear immediately, but after some time at this height.

5000-7000 Feeling of general fatigue, loss of strength, heaviness in the whole body. Pain in the temples. With sudden movements - dizziness. Lips acquire a blue-purple hue, body temperature rises. There may be bleeding from the nose and lungs. And sometimes stomach bleeding. There are hallucinations.

Altitude sickness is best overcome by acclimatization. Before the onset of the illness. Acclimatize in advance. Eat more vitamins and carbohydrates. The most important condition here is the complete rejection of the use of alcohol and nicotine.

In the event of an attack, first aid, as mentioned above, is the cessation of all physical exertion, in case of fainting, artificial respiration, rest.

Prevention of mountain sickness, we repeat - acclimatization. Take a break and rest. Let the body itself get used to this height, adapt to new conditions. But in very severe cases, an immediate descent into the valley is recommended. The mountain sickness will go away on its own. Preventive agents are: caffeine - 0.1 gr., Pyramidone - 0.3 gr., enhanced nutrition, vitamins, glucose with vitamin C.

Using Russian translation, Adventures in Diving PADI textbook and 1000+1 travel tips

What is rarefied air? Explain to me like a fool what rarefied air is ...

1. So the guys want to reassure everyone ... First of all, the molecules are not getting smaller! they simply move away from each other… It follows that the concentration of gases does not change, the volume of the gas mixture system changes! And this happens due to a decrease in pressure ... The gas mixture is like a spring, the more you squeeze it, the less volume it will eventually occupy ... The lower the potential pressure, the greater the volume! With the same concentration but a larger volume, our body must ventilate more air, but since the volume of the lungs has its maximum, and is unable to take in more, we experience malaise (hypoxia)
2. Now, if air is imagined as water, then in a liter jar there will be less than a liter and nothing else will be ... drops of water seem to recede from each other.
   So it is with air
3. You climb a high mountain and oops! And there is nothing to breathe))
   In general, this is low atmospheric pressure, observed at high altitudes.
4. 
   
   Hence the meaning of the word "rarefied" - air. in which molecules are located less often. Because there are just fewer of them.

   I saw. How do you pump up a ball? Air is pumped into it, there are more air molecules there, and since they always move randomly, they now more often hit the walls of the ball from the inside and put pressure on it. Therefore, the inflated ball is so elastic.
   Now imagine that the pump works in the opposite direction - it pumps out air. Of course, the ball will simply flatten - that's all. But if instead of a ball we have a rigid vessel - glass, metal, then it retains its shape and dimensions. But the air (and molecules) when pumping out in it becomes really less. This is what is called rarefied air.

   So rarefied air is obtained artificially. But it also happens in nature. Namely:
   the higher you climb from sea level into the mountains, the thinner the air becomes. Therefore, it is difficult to breathe high in the mountains, climbers even put on oxygen masks. And even higher, where planes fly, the air is even more rarefied. And if the sealing of the aircraft is broken, the passengers will die very quickly. You ask: why do planes climb so high if it's dangerous? Hard economic interests force this: rarefied air is much less dense than below, and therefore offers less resistance. This means that the aircraft can fly at a higher speed, the flight time is reduced, and fuel is saved.

   PS Isn't it time to take a break from physics? . Look at my page (in My world), look through photo albums ...

5. Anatoly Shodoev Enlightened (48195) 5 years ago
   First of all, I'm not going to explain like a fool. I will explain as a normal student who did not understand the topic a little.
   Secondly, well done. that you spell the word sparse correctly. So many people write discharge, maybe they even think that this word comes from the word "discharge".
   Actually. of course, the word "rarely" is at the heart of it.
   ======================================================
   And how to understand then how to defuse the AK 47 assault rifle? If this word is based on "rarely"?
6. There is such a thing as pressure. imagine that there is a certain amount of air in the piston, we pull the piston, and now the previous volume has doubled, and there is as much air left as it was before. this will be rarefied air, as opposed to, for example, the pressure of excess air in the tires of a car. And don't call yourself a fool, that's bad
7. “But how to understand then how to defuse the AK 47 assault rifle? If this word is based on “rarely”?
   Sparse comes from the word rarely.
   And discharge comes from the word discharge.

What is rarefied air? Explain to me like a fool what rarefied air is ...)) and got the best answer

Answer from Anatoly Shodoev[guru]



Hence the meaning of the word "rarefied" - air. in which molecules are located less often. Because there are just fewer of them.
I saw. How do you pump up a ball? Air is pumped into it, there are more air molecules there, and since they always move randomly, they now more often hit the walls of the ball from the inside and put pressure on it. Therefore, the inflated ball is so elastic.
Now imagine that the pump works in the opposite direction - it pumps out air. Of course, the ball will simply flatten - that's all. But if instead of a ball we have a rigid vessel - glass, metal, then it retains its shape and size. But the air (and molecules) when pumping out in it becomes really less. This is what is called rarefied air.
So rarefied air is obtained artificially. But it also happens in nature. Namely:
the higher you climb from sea level into the mountains, the thinner the air becomes. Therefore, it is difficult to breathe high in the mountains, climbers even put on oxygen masks. And even higher, where planes fly, the air is even more rarefied. And if the sealing of the aircraft is broken, the passengers will die very quickly. You ask: why do planes climb so high if it's dangerous? Hard economic interests are forcing this: rarefied air is much less dense than below, and therefore offers less resistance. This means that the aircraft can fly at a higher speed, the flight time is reduced, and fuel is saved.
PS Isn't it time to take a break from physics? . Look at my page (in My world), look through photo albums...

Answer from 2 answers[guru]

Hey! Here is a selection of topics with answers to your question: What is rarefied air? Explain to me like a fool what rarefied air is ...))

Answer from ForShmak[guru]
Now, if air is imagined as water, then in a liter jar there will be less than a liter and nothing else will be ... drops of water seem to recede from each other.
So it is with air

Answer from Stealthy[guru]
You climb a high mountain and oops! And there is nothing to breathe))
In general, this is low atmospheric pressure, observed at high altitudes.

Answer from Alexander[guru]
There is such a thing as pressure. imagine that there is a certain amount of air in the piston, we pull the piston, and now the previous volume has doubled, and there is as much air left as it was before. this will be rarefied air, as opposed to, for example, the pressure of excess air in the tires of a car. And don't call yourself a fool, that's bad

Answer from Yoalikaly Güntner[active]
Anatoly Shodoev Enlightened (48195) 5 years ago
First of all, I'm not going to explain like a fool. I will explain as a normal student who did not understand the topic a little.
Secondly, well done. that you spell the word sparse correctly. So many people write discharged, maybe they even think that this word comes from the word "discharge".
Actually. Of course, the word "rarely" is at the heart of it.
======================================================
And how to understand then how to defuse the AK 47 assault rifle? If this word is based on "rarely"?

Answer from ..|.. [newbie]
"But how to understand then how to defuse the AK 47 assault rifle? If this word is based on" rarely "?"
Sparse comes from the word rarely.
And discharge comes from the word discharge.

Answer from Alan Tedeshvili[newbie]
So guys, I want to reassure everyone... First of all, there are no fewer molecules! they simply move away from each other ... It follows that the concentration of gases does not change, the volume of the gas mixture system changes! And this happens due to a decrease in pressure ... The gas mixture is like a spring, the more you squeeze it, the less volume it will eventually occupy ... The lower the potential pressure, the greater the volume! With the same concentration but a larger volume, our body must ventilate more air, but since the volume of the lungs has its maximum, and is unable to take more, we experience malaise (hypoxia)

May 29 marks exactly 66 years since the first ascent of the highest mountain in the world - Everest. After many attempts by different expeditions in 1953, New Zealander Edmund Hillary and Nepalese Sherpa Tenzing Norgay reached the world peak - 8848 meters above sea level.

To date, more than nine thousand people have already conquered Everest, while more than 300 have died during the ascent. Will a person turn around 150 meters before conquering the summit and go down if another climber becomes ill, and is it possible to climb Everest without oxygen - in our material.

Conquer the summit or save someone else's life

There are more and more people wishing to conquer the highest peak of the world every year. They are not afraid of the price of climbing, measured in tens of thousands of dollars (only one climbing permit costs $11,000, as well as the services of a guide, Sherpas, overalls and equipment), nor the risk to health and life. At the same time, many go completely unprepared: they are attracted by the romance of the mountains and the blind desire to conquer the peak, and this is the hardest test of survival. For the spring season 2019, there are already 10 people on Everest. According to media reports, a total of 20 people died in the Himalayas this spring, which is more than in all of 2018.

Of course, there is a lot of commerce in extreme tourism now, and climbers with many years of experience also note this. If earlier the queue for climbing Everest had to wait for years, now getting permission for the next season is not a problem. This spring alone, Nepal has sold 381 lifting licenses. Because of this, many hours of queues of tourists formed on the approaches to the top of the mountain, and this is at heights that are critical for life. There are situations when oxygen runs out or there are not enough physical resources of the body to stay in such conditions, and people can no longer walk, someone dies. In cases where one of the members of the group became ill, the rest have a question: leave him and continue on his way to achieve the goal for which they have been preparing all their lives, or turn around and go downhill, saving the life of another person?

According to mountaineer Nikolai Totmyanin, who has made more than 200 ascents (including five ascents of eight-thousanders and 53 ascents of seven-thousanders), it is not customary in Russian groups in mountain expeditions to leave a person who cannot go further. If someone becomes ill and there are big health risks, then the whole group turns around and goes down. This happened more than once in his practice: it happened that he had to deploy the entire expedition 150 meters from the goal (by the way, Nikolai himself climbed to the top of Everest twice without an oxygen tank).

There are situations when it is impossible to save a person. But just leaving him and continuing to move, knowing that he could die or spoil his health - this, according to our concepts, is nonsense, simply unacceptable. Human life is more important than any mountain.

At the same time, Totmyanin notes that it is different on Everest, since commercial groups from different countries are gathered there: “Others, for example, the Japanese, do not have such principles. Everyone is there for himself and is aware of the measure of responsibility that he can stay there forever ". Another important point: non-professional climbers do not have a sense of danger, they do not see it. And, being in an extreme situation, when there is little oxygen, the body is limited to any activity, including mental. “In such a situation, people make inadequate decisions, so it’s impossible to entrust a person with a decision about whether to continue moving or not. This should be done by the leader of the group or expedition,” sums up Totmyanin.

oxygen starvation

What happens to a person at such a height? Imagine that you yourself decided to conquer the summit. Due to the fact that we get used to high atmospheric pressure, living in a city almost on a plateau (for Moscow, this is an average of 156 meters above sea level), getting into a mountainous area, our body experiences stress.

This is because the mountain climate is, first of all, low atmospheric pressure and more rarefied air than at sea level. Contrary to popular belief, the amount of oxygen in the air does not change with height, only its partial pressure (voltage) decreases.

That is, when we breathe rarefied air, oxygen is not absorbed as well as at low altitudes. As a result, the amount of oxygen entering the body decreases - a person experiences oxygen starvation.

That is why when we come to the mountains, often instead of the joy of clean air overflowing our lungs, we get headaches, nausea, shortness of breath and severe fatigue even during a short walk.

Oxygen starvation (hypoxia)- the state of oxygen starvation of both the whole organism as a whole and individual organs and tissues, caused by various factors: breath holding, disease states, low oxygen content in the atmosphere.

And the higher and faster we climb, the worse the health consequences can be. At high altitudes, there is a risk of developing altitude sickness.

What are the heights:

• up to 1500 meters - low altitudes (even with hard work there are no physiological changes);
• 1500-2500 meters - intermediate (physiological changes are noticeable, blood oxygen saturation is less than 90 percent (normal), the likelihood of mountain sickness is low);
• 2500-3500 meters - high altitudes (mountain sickness develops with a rapid ascent);
• 3500-5800 meters - very high altitudes (altitude sickness often develops, blood oxygen saturation is less than 90 percent, significant hypoxemia (decrease in oxygen concentration in the blood during exercise);
• over 5800 meters - extreme heights (pronounced hypoxemia at rest, progressive deterioration, despite maximum acclimatization, permanent stay at such heights is impossible).

altitude sickness- a painful condition associated with oxygen starvation due to a decrease in the partial pressure of oxygen in the inhaled air. Occurs high in the mountains, starting at about 2000 meters and above.

Everest without oxygen

The highest peak in the world is the dream of many climbers. Awareness of the unconquered hugeness 8848 meters high has excited minds since the beginning of the last century. However, for the first time people were on its top only in the middle of the twentieth century - on May 29, 1953, the mountain finally submitted to the New Zealander Edmund Hillary and the Nepalese Sherpa Tenzing Norgay.

In the summer of 1980, a man overcame another obstacle - the famous Italian climber Reinhold Messner climbed Everest without auxiliary oxygen in special cylinders that are used on climbs.

Many professional climbers, as well as doctors, pay attention to the difference in the sensations of the two climbers - Norgay and Messner, when they were at the top.

According to the memoirs of Tenzing Norgay, "the sun was shining, and the sky - in all my life I have not seen the sky blue! I looked down and recognized the places memorable from past expeditions ... On all sides around us were the great Himalayas ... I had never seen such a sight and never I will not see again - wild, beautiful and terrible.

And here are Messner's memories of the same peak. “I’m sinking into the snow, heavy as a stone from fatigue… But they don’t rest here.

What is the reason for such a significant difference in the description of their triumphant ascent of the two climbers? The answer is simple - Reinhold Messner, unlike Norgay and Hillary, did not breathe oxygen.

Inhaling at the top of Everest will bring three times less oxygen to the brain than at sea level. That is why most climbers prefer to conquer peaks using oxygen tanks.

On eight-thousanders (peaks above 8000 meters) there is a so-called death zone - a height at which, due to cold and lack of oxygen, a person cannot stay for a long time.

Many climbers note that doing the simplest things - tying shoes, boiling water or getting dressed - becomes extraordinarily difficult.

Our brain suffers the most during oxygen starvation. It uses 10 times more oxygen than all other parts of the body combined. Above 7500 meters, a person receives so little oxygen that there may be a violation of the blood flow to the brain and its swelling.

Cerebral edema is a pathological process manifested by excessive accumulation of fluid in the cells of the brain or spinal cord and intercellular space, an increase in brain volume.

At an altitude of more than 6000 meters, the brain suffers so much that temporary bouts of insanity can occur. Slow reaction can be replaced by excitement and even inappropriate behavior.

For example, the most experienced American guide and climber Scott Fisher, most likely, having received cerebral edema, at an altitude of more than 7000 meters asked to call him a helicopter for evacuation. Although in a normal state, any, even not very experienced climber, knows perfectly well that helicopters do not fly to such a height. This incident occurred during the infamous climb of Everest in 1996, when eight climbers died during a storm on the descent.

This tragedy was widely known due to the large number of dead climbers. The victims of the ascent on May 11, 1996 were 8 people, including two guides. On that day, several commercial expeditions climbed to the top at the same time. Participants of such expeditions pay money to the guides, who, in turn, provide maximum safety and comfort for their clients on the route.

Most of the participants in the 1996 climb were not professional climbers and were heavily dependent on supplemental oxygen in cylinders. According to various testimonies, 34 people simultaneously went to the summit that day, which significantly delayed the ascent. As a result, the last climber reached the summit after 16:00. The critical time for the ascent is considered to be 13:00, after this time the guides are required to turn the clients back in order to have time to go down while it is light. 20 years ago, neither of the two guides gave such an order in time.

Due to the late rise, many participants did not have oxygen for the descent, during which a strong hurricane hit the mountain. As a result, after midnight, many climbers were still on the side of the mountain. Without oxygen and due to poor visibility, they could not find their way to the camp. Some of them were rescued by professional climber Anatoly Bukreev alone. Eight people died on the mountain due to hypothermia and lack of oxygen.

About mountain air and acclimatization

And yet, our body can adapt to very difficult conditions, including high mountains. In order to be at an altitude of more than 2500-3000 meters without serious consequences, an ordinary person needs from one to four days of acclimatization.

As for altitudes above 5000 meters, it is practically impossible to adapt to them normally, so you can only stay at them for a limited time. The body at such heights is not able to rest and recover.

Can the health risks of being at altitude be reduced and how can this be done? As a rule, all health problems in the mountains begin due to insufficient or improper preparation of the body, namely the lack of acclimatization.

Acclimatization is the sum of adaptive-compensatory reactions of the body, as a result of which a good general condition is maintained, weight is maintained, normal working capacity and psychological state are maintained.

Many medical professionals and mountaineers believe that the best way to adjust to altitude is to climb gradually - make several ascents, reaching ever greater heights, and then descend and rest as low as possible.

Imagine a situation: a traveler who decides to conquer Elbrus, the highest peak in Europe, starts his journey from Moscow from 156 meters above sea level. And in four days it turns out to be 5642 meters.

And although adaptation to altitude is genetically inherent in us, such a negligent climber faces several days of heart palpitations, insomnia and headaches. But for a climber who plans to climb at least a week, these problems will be minimized.

While a resident of the mountainous regions of Kabardino-Balkaria will not have them at all. In the blood of highlanders from birth, there are more erythrocytes (red blood cells), and the lung capacity is on average two liters more.

How to protect yourself in the mountains when skiing or hiking

• Gradually gain altitude and avoid sudden elevation changes;
• If you feel unwell, reduce the time of skiing or walking, make more stops for rest, drink warm tea;
• Due to the high ultraviolet radiation, retinal burns can occur. To avoid this in the mountains, you need to use sunglasses and a hat;
• Bananas, chocolate, muesli, cereals and nuts help fight oxygen starvation;
• Alcoholic drinks at altitude should not be consumed - they increase dehydration of the body and exacerbate the lack of oxygen.

Another interesting and, at first glance, obvious fact is that in the mountains a person moves much more slowly than on the plain. In normal life, we walk at a speed of about 5 kilometers per hour. This means that we cover a distance of a kilometer in 12 minutes.

To climb to the top of Elbrus (5642 meters), starting from a height of 3800 meters, a healthy acclimatized person on average will need about 12 hours. That is, the speed will drop to 130 meters per hour compared to normal.

Comparing these figures, it is not difficult to understand how seriously altitude affects our body.

Tenth tourist dies on Everest this spring

Why the higher the colder

Even those who have never been in the mountains know one more feature of the mountain air - the higher, the colder. Why is this happening, because closer to the sun, the air, on the contrary, should warm up more.

The thing is that we feel heat not from the air, it heats up very badly, but from the surface of the earth. That is, a ray of the sun comes from above, through the air and does not heat it.

And the earth or water receives this beam, heats up quickly enough and gives off heat upwards, to the air. Therefore, the higher we are from the plain, the less heat we receive from the earth.

Inna Lobanova, Natalia Loskutnikova

Air density decreases with distance from the earth's surface. This is because the pressure in the upper atmosphere is lower than at the ground.

What is the relationship between air pressure and its density?

The density of a gas is directly proportional to its pressure. The dependence of air density on pressure describes the Clapeyron equation: for an ideal gas

,

where ? - air density, p- absolute pressure, R- specific gas constant for dry air (287.058 J? (kg K)), T is the absolute temperature in Kelvin.

To calculate air density ? at a certain height above sea level h the following formulas are used:

, where

Here
p0- standard atmospheric pressure at sea level (101325 Pa);
T0- standard temperature at sea level (288.15 K);
g- acceleration of free fall over the Earth's surface (9.8 m?sec 2);
L- the rate of temperature drop with height, within the troposphere (0.0065 K?m);
R- universal gas constant (8.31447 J? (Mol K));
M- molar mass of dry air (0.0289644 kg? Mol).

This is understandable and intuitive: the lower layers of air are under more pressure than the upper ones.

What does low pressure and low air density mean? This means that such rarefied air contains fewer molecules, including oxygen molecules. That's why it's hard to breathe at high altitude.

By the way...

At 0 ° C, the mass of one cubic meter (1 m 3) of air is:

• at the surface of the earth - 1, 293 kilograms;
• at an altitude of 12 km - 319 grams;
• at an altitude of 40 km - 4 grams.