What Is Air Pressure?

Air pressure is the atmospheric pressure acting on a unit area, which is numerically equal to the gravitational force experienced by a vertical column of air that extends upward to the upper boundary of the atmosphere on a unit area basis. The famous Madenburg Hemisphere experiment proved its existence. The international unit of pressure is Pascal, abbreviated Pa, and the symbol is Pa ^[1] . In meteorology, people generally use kilopascals (kPa) or hundred pascals (hpa) as units. Other commonly used units are: bar (1 bar = 100,000 Pa) and centimeter mercury column (or centimeter mercury). Air pressure varies not only with altitude, but also with temperature. Changes in air pressure are closely related to changes in weather. ^[2]

Abbreviation for atmospheric pressure. It is the atmospheric pressure acting on the unit area, which is equal to the weight of the vertical air column that extends upward to the upper boundary of the atmosphere on the unit area. Pressure is related to conditions such as altitude and temperature. It generally decreases with height. In the horizontal direction, the difference in atmospheric pressure causes air to flow. A unit that indicates air pressure. The mercury column height is customarily used. For example, a standard atmospheric pressure is equal to the weight of a mercury column that is 760 millimeters high, which is equivalent to an atmospheric pressure of 1.0336 kilograms per square centimeter. The international standard uniformly uses "100 Pa" as the unit of pressure. After conversion: One standard atmospheric pressure = 1013 hectopascals (mbar). Shenzhen's annual average pressure is 1009.8 hectopascals. ^[1]

Standard atmospheric pressure. A unit of air pressure, commonly used in practice

Meteorological commonly used measuring instruments are liquids (such as mercury)

There are usually equilibrium conditions and

1MPa (megapascal) = 1000kPa (kilopascal) = 1000000Pa (pascal)

1bar (bar) = 0.1MPa

1atm (standard atmospheric pressure) = 0.1013MPa = 1.013bar = 760mmHg = 10.33mH ₂ O

1kgf / cm ² (engineering kilogram force) = 0.981bar = 0.0981Mpa

1psi Lb / in ² = 0.07031kgf / cm ² = 0.06893 bar = 6.893kpa

1MPa = 145psi

Psi (lb / in ² ) pounds /

The pressure and altitude, atmospheric temperature,

Instruments for measuring air pressure, the most common are

After a lot of experiments in October 1640, Tori

The impact of air pressure on human health can be summarized into two aspects, physiological and psychological. The effect of low air pressure on human physiology mainly affects the supply of oxygen in the human body. Due to the lack of oxygen in the human body, the symptoms of dizziness, headache, nausea, vomiting, and weakness can also occur. Nervous system disorders can also occur, and even pulmonary edema and coma can occur. This is commonly referred to as the "alpine response."

In a high-pressure environment, the body's tissues are gradually saturated with nitrogen (generally, the body is saturated with nitrogen after working under high pressure for 5-6 hours). When the body returns to standard atmospheric pressure, the excess nitrogen in the body will be exhaled. It is discharged slowly, but this process is relatively slow. If it suddenly returns from the high-pressure environment to the standard atmospheric pressure environment, part of the nitrogen accumulated in fat may stay in the body and expand to form small air bubbles, which will block blood and tissues and easily form gas. Symptoms can cause illness, and severe cases can endanger human life.

The impact of pressure changes on human health is more manifested in the generation, disappearance, or movement of the circulation weather situation represented by high or low pressure. Under the circumstance of low-pressure circulation, it is mostly rainy weather, and the change of wind is relatively obvious; while under the circumstance of high-pressure circulation, it is mostly sunny and the weather is relatively stable. Under the control of high pressure, the air is dry, the weather is fine, and the radiant cooling at night is easy to form a ground-covering inversion layer. Allergens such as dust, fungi, pollen, and spores are likely to stagnate near the ground, which can induce asthma attacks.

At the same time, changes in air pressure will also affect people's psychological changes, making people feel depressed and depressed. For example, rain and snow under low pressure, especially high temperature and high humidity before the thunderstorm in summer (at this time, the pressure is low), people with poor cardiopulmonary function will be extremely uncomfortable, and normal people also have a sense of depression and discomfort. And this kind of suffocation and depression will make people's autonomic nerves tend to be tense, release adrenaline, cause blood pressure to rise, heart rate will increase, shortness of breath, etc. At the same time, cortisol will be broken down, causing increased gastric acid secretion, blood vessel prone to infarction, Blood sugar levels may also rise sharply. Some scholars conducted a comparative study of the lowest monthly pressure and the peak of death, and found that 89% of the peaks of death occurred during the lowest pressure ^[3] .