What is the concept of smog 500?

Haze 500 indicates heavy air pollution.

Haze index, also known as PM2.5 index, refers to the concentration of suspended solids and fine particulate matter (PM2.5) in the air, and is an important indicator to measure the degree of air pollution.

The smog index was put forward by the Ministry of Environmental Protection of China and implemented by China National Environmental Monitoring Center. According to the air quality status, it is divided into level 1 to level 6, and * * is divided into six indexes: excellent, good, light pollution, moderate pollution, heavy pollution and serious pollution. The corresponding PM2.5 indicators are 0-35, 35-75, 75- 1 15 respectively.

Generally speaking, the air quality below the excellent level is good and you can go out safely, but you should pay attention to protect yourself. When the air quality is slightly polluted, outdoor activities should be minimized and masks should be used when necessary. When the air quality is seriously polluted, outdoor activities should be minimized.

Composition of smoke:

Haze is composed of particles such as dust, sulfuric acid, nitric acid and organic hydrocarbons in the air. It will also make the atmosphere turbid, blur the vision and worsen the visibility. If the horizontal visibility is less than 65,438+00,000 meters, the sight distance obstacle caused by this non-aqueous aerosol system is called haze or dust haze, and the Hong Kong Observatory calls it haze.

Haze is mainly composed of sulfur dioxide, nitrogen oxides and inhalable particles. The first two are gaseous pollutants, and the last particulate matter is the main reason for aggravating smog weather pollution. Together with the fog, they make the sky gloomy in an instant.

The abbreviation of particulate matter is PM, and Beijing monitors fine particulate matter (PM2.5), that is, pollutant particles with aerodynamic equivalent diameter less than or equal to 2.5 microns. This particle itself is not only a pollutant, but also a carrier of toxic substances such as heavy metals and polycyclic aromatic hydrocarbons.

Above content reference: Baidu Encyclopedia-Smog