Air quality deteriorated significantly on September 14. A total of four regions experienced unhealthy conditions. The highest reading was recorded in one area, which reached a level of 136.

Winds shifting east-southeast caused smoke from fires to drift towards the affected regions. This smoke originated from fires in Kalimantan and southern Sumatra.

Further information is available from the National Environment Agency's haze advisory, as reported by Channel NewsAsia on September 14.