Air

Air is a mixture of gases that make up the Earth's atmosphere. When assessing air quality, the chemical composition, physical parameters (temperature, humidity, speed, barometric pressure) and the presence of mechanical impurities (for example, dust and microorganisms) are taken into account.

The largest contribution to the air composition is made by nitrogen (78.09% by volume) and oxygen (20.95%). Oxygen is the most important gas for humans and animals. The Earth's atmosphere contains about 1.18·10^13 tons of oxygen. Plants annually release about 0.5·10^-12 tons of oxygen, which allows replenishing its reserves in the atmosphere. The more plants surround us, the cleaner and richer in oxygen the air becomes.

The human body needs oxygen to maintain life. At rest, oxygen demand ranges from 12 to 17 liters per hour, and with physical activity it increases. It is important to note that the amount of oxygen saturation in the blood does not depend on the percentage of oxygen in the air, but on the partial pressure of oxygen. The partial pressure of oxygen is that part of the total atmospheric pressure that is due to oxygen.

At sea level, the oxygen content in the air is 20.9%, and the partial pressure is 158.84 mmHg. In the alveolar air, which is located in the pulmonary alveoli, the oxygen content does not exceed 14.5%, and the partial pressure is 103.38 mm Hg. In venous blood, the partial pressure of oxygen is even lower and is equal to 40 mmHg. The difference in partial pressure ensures the transition of oxygen from the alveolar air into the blood, and then through the membranes into the tissue fluid.

When climbing mountains, the partial pressure of oxygen decreases in proportion to the decrease in barometric pressure. At an altitude of 1000 meters above sea level, the barometric pressure is 674 mmHg and the partial pressure of oxygen is 141 mmHg. At an altitude of 3000 meters, 525.98 and 110 mmHg, respectively. A decrease in the partial pressure of oxygen in the air affects the state of the body. At a partial pressure of oxygen of 140 mmHg, the first signs of oxygen starvation - hypoxia - are observed. When it drops to 110 mmHg, a person may experience severe discomfort, and with prolonged stay at this altitude, serious health consequences are possible.

In addition, the air may contain various pollutants, such as carbon dioxide, nitrogen oxides, sulfur dioxide, ozone and many others. These substances can negatively affect human health and the environment. Therefore, it is very important to monitor air quality and take measures to protect and improve it. Such measures may include the use of environmentally friendly technologies, reducing pollutant emissions, encouraging the use of public transport and bicycles instead of cars, as well as the development of green technologies and green spaces.