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Air Quality


◆ What is Ozone?

Ozone (O3) is a photochemical oxidant produced by a series of reactions between nitrogen oxide and hydrocarbons under the action of ultraviolet light (other photochemical oxidants include O3, acrolein, PAN, and Acetyl Nitrate), and is considered a secondary pollutant. It is has a distinctively pungent smell and is a strong oxidizing agent. Volatile organic compounds (VOCs), one of the ozone precursors, are emitted by automobiles, chemical processing plants, oil refineries, road markings, paints and coatings, the printing industry, and dry cleaning chemicals, and a large amount is emitted naturally by forests as well. Ozone serves to protect the Earth's ecosystem by blocking ultraviolet radiation in the stratosphere. It is created in the troposphere through photochemical reactions involving naturally produced ozone precursors.

Repeated exposure to ozone can damage the lungs, induce chest pain, and cause coughing and nausea. It can also affect the digestive system. In severe cases, it can exacerbate respiratory and heart conditions, pulmonary emphysema, and asthma. People with respiratory conditions, the elderly, and children are particularly affected by ozone, making it necessary for them to take extra care when ozone concentrations are high. Ozone can also directly affect crops and plants, as it causes the leaves to wither, reducing crop yield.

◆ Forecast Levels and Citizen Action Plan Instructions

Forecast Levels and Citizen Action Plan Instructions
Forecast Level Good Moderate Unhealthy Very Unhealthy
Forecast Concentration (ppm) 0~0.030 0.031~0.090 0.091~0.150 Over 0.151
Instructions for Citizens (Sensitive Groups) No need to change usual outdoor activities, but only engage in such activities after considering the status of your health Avoid spending long periods of time outdoors or engaging in strenuous outdoor activities. Stay indoors as much as possible.
Instructions for Citizens (General) Avoid spending long periods of time outdoors or engaging in strenuous outdoor activities. In particular, anyone experiencing discomfort such as sore eyes should avoid outdoor activities. Limit outdoor activities. People are advised to stay indoors.

(※ Sensitive Groups: Children, the elderly, the infirm, and adults suffering from asthma and other respiratory or heart conditions)

◆ Warning Notification Zones (5 Zones)

Alert Levels and Instructions for Citizens
Zone Number of Districts Administrative Districts Map of Zones
Central 3 Jongno, Jung, Yongsan Warning Notification Zones (5 Zones)
Northeastern 8 Seongdong, Gwangjin, Dongdaemun, Jungnang, Seongbuk, Gangbuk, Dobong, Nowon
Northwestern 3 Mapo, Seodaemun, Eunpyeong
Southwestern 7 Yangcheon, Gangseo, Guro, Geumcheon, Yeongdeungpo, Dongjak, Gwanak
Southeastern 4 Seocho, Gangnam, Songpa, Gangdong

※ Warning notifications for ozone are issued according to the zones designated above.

◆ Alert Levels and Instructions for Citizens

Alert Levels and Instructions for Citizens
Level Criteria Instructions for Citizens
General Vehicle Owners
Advisory Hourly average is over 0.12ppm ▪ Outdoor incineration is prohibited. ▪ Drivers are advised to refrain from driving within the alert area (establishment of carpool system is recommended)
▪ Use of public transportation is advised ▪ Use of public transportation is advised
▪ Refrain from outdoor and strenuous activities. ▪ Drivers are advised to refrain from any unnecessary driving.
▪ The elderly, the infirm, children, and people with respiratory or heart conditions are advised to refrain from outdoor activities.
Warning Hourly average is over 0.30ppm ▪ Outdoor incineration is prohibited. ▪ If possible, avoid driving within the alert area.
▪ Limit outdoor and strenuous activities
▪ Kindergartens and schools are advised to limit outdoor activities.
▪ The elderly, the infirm, children, and people with respiratory or heart conditions are advised to limit outdoor activities.
Serious Warning Hourly average is over 0.50ppm ▪ The operation of incineration facilities is to be suspended. ▪ Driving is prohibited within the alert area.
▪ Outdoor and strenuous activities are prohibited.
▪ Kindergartens and schools are advised to suspend outdoor activities and close for the day.
▪ The elderly, the infirm, children, and people with respiratory or heart conditions are advised to refrain from outdoor activities.