A mass of thick smog blanketed the whole Ningbo on December 4. According to the real-time data of AQI (air quality index), from 4pm, the air pollution worsened. At 8.20 in the evening, Ningbo Meteorological Station upgraded the yellow-level haze warning to the orange-level warning, which is said to be the first issued in 2013.
　　Experts from Ningbo Environmental Protection Bureau pointed out that as the humidity in the air was high on December 4, it can be referred to as “smog”, while it was “haze” the days before. Comparatively speaking, smog is more hazardous to people’s health, with the major pollutants being PM2.5.
　　According to the warning, the visibility in most parts of the city was less than 3,000 meters due to the smog, and the air quality can be classified as moderate or heavy pollution during the night, which was not good for the dispersion of the pollutants. It is said that the weather condition will continue on December 5.
　　On October 30, Ningbo Meteorological Station issued the first yellow-level haze warning in fall. Then on December 4, it was the second time to see the yellow-level warning, which had a longer duration, wider range and more serious impact.
　　The first meteorological haze warning, a yellow-level one, in Ningbo’s history occurred on June 13, 2012. Then on November 1 the same year, an orange-level haze warning was issued by the meteorological station.
　　According to experts from the environment monitoring center, the weather on December 4 was both haze and fog. Haze and fog are different although quite similar. The relative humidity of fog is above 90%, while that of haze is below 80%. The smog is the mixture of haze and fog, with the humidity between 80% and 90%.
　　Experts say the smog has a greater impact on human health as the air with such a high humidity may absorb more floating toxic and harmful substances in the air. Therefore, citizens are advised to minimize their time outdoors, especially for vigorous activities outdoors and to wear a face mask if necessary.