On the Earth, the normal air composition is calculated by volume fraction: nitrogen (N2) accounts for about 78%, oxygen (O2) accounts for about 21%, rare gas accounts for about 0.939%, and carbon dioxide (CO2) accounts for about 0.031%. Other gases and impurities account for approximately 0.03%, such as ozone (O3), nitric oxide (NO), nitrogen dioxide (NO2), and water vapor (H2O). Because the environment in different parts of the earth directly affects the air quality in various places, the situation is quite complicated. Therefore, only the human settlement environment is discussed here, which is a relatively closed air quality problem in the human living space.
If the normal air composition changes, it will have a great impact on the body that depends on the air to survive, that is, the air is polluted. In the human environment, there are four major types of air pollutants: particulate matter, planktonic bacteria, volatile organic compounds (VOCs), and inorganic matter.
During the flow of air, it will carry many tiny particles, including dust, sea salt, plant pollen, and spores. We often hear that PM2.5, PM10, is an indicator of the concentration of different particle sizes.
Phytoplankton refers to fungi, bacteria, viruses, etc. suspended in the air, including ticks, cockroaches, cat and dog allergens, penicillium, aspergillus, staphylococci, spheroids, and the like.
VOCs include volatile organic compounds such as formaldehyde, toluene, xylene, styrene, benzo[a]pyrene, hydrocarbons, and lipids. The main sources are various furniture, chemical products, paints, adhesives, and fuels in the living environment.
Including ammonia, carbon monoxide, carbon dioxide, ozone, nitrogen oxides, sulfur dioxide and other sulfides. These substances are mainly due to environmental changes, biological excretion, air flow, etc. and have more or less impact on the human body.