Tourists wear masks on a visit to Tian'anmen Square on the third day of hazardous air quality in central Beijing yesterday. Air pollution in the Chinese capital again reached dangerous levels. The municipal meteorological station issued the city's first orange fog warning in the morning due to decreased visibility caused by the heavy smog. Monitoring data released yesterday showed that air quality indexes in most regions of Beijing had hit 500, the indexes' highest level. Many residents chose to stay indoors and emergency action was taken to tackle the problem. [Shanghai Daily]