What benefits does air bring to people

Among us, we cannot live without air. Oxygen in the air is a substance necessary for life. Although air is so important, many people do not take it very seriously, especially now that air quality problems such as smog have begun to appear in many places. Today we will give you a detailed introduction to air knowledge, and we hope that everyone can pay attention to our air quality issues.

Air refers to the mixture of gases in the earth's atmosphere. Therefore, air is a mixture, which is mainly composed of nitrogen, oxygen, rare gases (helium, neon, argon, krypton, xenon, radon), carbon dioxide and other substances (such as water vapor, impurities, etc.). The volume fraction of nitrogen is about 78%, the volume fraction of oxygen is about 21%, the volume fraction of rare gases (helium, neon, argon, krypton, xenon, radon) is about 0.934%, the volume fraction of carbon dioxide is about 0.04% (the latest data in 2017), and the volume fraction of other substances (such as water vapor, impurities, etc.) is about 0.002%. The composition of air is not fixed. The proportion of air will change with changes in altitude and air pressure. But for a long time people believed that air was a single substance until later the French scientist Lavoisier first concluded through experiments that air is composed of oxygen and nitrogen. At the end of the 19th century, scientists discovered through a large number of experiments that there are also rare gases such as helium, argon, and xenon in the air.

In its natural state, air is colorless and odorless.

Oxygen in the air is essential for all aerobic organisms. All animals need to breathe oxygen, and green plants also need oxygen for respiration. In addition, green plants use carbon dioxide in the air for photosynthesis, and air is almost the only source of carbon dioxide needed by all plants.

Air is a mixture of many gases. Its constant components are rare gases such as oxygen, nitrogen, argon and neon, and its variable components are carbon dioxide and water vapor. Their content in the air varies slightly within a very small range depending on the geographical location and temperature. As for the uncertain components in the air, they vary with different regions. For example, places near metallurgical plants will contain sulfur dioxide, places near chlorine-alkali plants will contain chlorine, and so on. In addition, there are trace amounts of hydrogen, ozone, nitrous oxide, methane and more or less dust in the air.

Experiments have shown that the percentage of constant components in the air is almost constant within an altitude of 100 km from the ground. By volume content, oxygen accounts for about 20.95%, nitrogen accounts for about 78.09%, and rare gases account for about 0.934%.

Generally speaking, the composition of air is relatively fixed. This is very important for the survival of humans and other animals and plants. However, with the development of modern industry, harmful gases and smoke emitted into the air have changed the composition of the air and caused air pollution. Polluted air can seriously damage human health, affect crop growth, and cause damage to natural resources and buildings.

Harmful substances emitted into the air can be roughly divided into two categories: dust and gas. From a global perspective, the most common gaseous pollutants emitted into the air are sulfur dioxide, carbon monoxide, nitrogen dioxide, etc. These gases come mainly from the burning of fossil fuels (coal and oil) and from factory exhaust.