Much of Taiwan, including Taipei in the north was experiencing good to moderate air quality on Sunday. But authorities were urging sensitive groups in the south to be on alert.
The Environmental Protection Administration's Taiwan Air Quality Monitoring Network showed mostly yellow � or moderate � markers in the north, with a scattering of green markers which denote good air quality.
But by 9am, areas in central Taiwan, including parts of Nantou, Yunlin, Chiayi, Tainan, Kaohsiung and Pingtung, were flashing orange markers. That means the air quality is unhealthy for young children, the elderly and people with chronic diseases.
The EPA's six-color scale takes into account ozone, PM2.5 and PM10 particulates, carbon monoxide, sulfur dioxide and nitric oxide concentrations in the air.
As of Sunday afternoon, the unhealthiest air was recorded in the Zuoying District of Kaohsiung, southern Taiwan. That area saw a reading of 152, which puts it just into the unhealthy category, with a red marker.
There are two worse categories in the scale: purple (201-300), which is very unhealthy; and maroon (301-500), which is hazardous.
Source: Radio Taiwan International