Singapore haze: BBC's David Shukman explains
21 June 2013 Last updated at 19:15 BST
Pollution levels reached a new record high for a third day in a row in Singapore, as smoky haze from fires in Indonesia shrouded the city state.
The Pollutant Standards Index (PSI) hit 401 at 12:00 on Friday (04:00 GMT) - the highest in Singapore's history.
The index also reached 400 in one part of Indonesia, which is readying helicopters and cloud-seeding equipment in an effort to tackle the fires.
Schools in parts of Malaysia and Indonesia have closed temporarily.
David Shukman reports.