1.   Thus ashtrays are often filled to overflow, and employees are spotted hacking and choking from the often dense smog.

2.   Yellow pines, which are among the most vulnerable, defend themselves by growing dormant in dense smog, then opening up when danger is past.

3.   Dense smog from forest fires has forced two airports to shut on Borneo Island, local reports said Thursday.

4.   In Taipei, the capital, dense smog is a daily nightmare for millions of people.

5.   Gummer also claimed that the dense smog which hangs over the major urban centres in Britain during summer and winter would be eliminated by the new clean air drive.