An ozone alert is a public notification issued when the level of ozone at ground level (also called "bad" ozone) rises to a concentration that may be harmful to people's health. Ground-level ozone is a major component of urban smog and is created by chemical reactions between pollutants like nitrogen oxides and volatile organic compounds in the presence of sunlight, especially on hot, sunny days. An ozone alert warns that the air quality is unhealthy, particularly for sensitive groups such as children, the elderly, people with respiratory issues, and those who are active outdoors. Exposure to high ozone levels can irritate the respiratory system, reduce lung function, aggravate asthma, cause chest pain, coughing, wheezing, and other breathing difficulties. The alert encourages people to limit outdoor activities and reduce emissions by using public transportation or combining errands. There are different levels of alerts, one indicating unhealthy air for sensitive groups and a higher level indicating air unhealthy for everyone. In summary, an ozone alert is a warning about unsafe outdoor air quality due to elevated ground-level ozone pollution, prompting the public to take precautions to protect health and reduce ozone-forming emissions.