Air quality hits unhealthy range in central, western Singapore
Smoke from southern Sumatra was drifting towards Singapore, with a continued risk of transboundary haze.
A view of the haze in central Bishan on the afternoon of Oct 5, 2026. (Photo: CNA/Marcus Mark Ramos)
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SINGAPORE: Air quality in central and western Singapore entered the unhealthy range on Monday (Oct 5).
The 24-hour Pollutant Standards Index (PSI) reading went up steadily, hitting 120 in the central region and 114 in the west at 3pm. Air quality for the rest of the island remained in the moderate range.
The 1-hour PM2.5 reading, which gives a more current indication of air quality, was elevated in the central, west, north and east at 3pm.
For immediate outdoor activities, people should refer to the 1-hour PM2.5 readings and corresponding personal guide, the National Environment Agency (NEA) said.
The 24-hour PSI forecast and health advisories should be used when planning outdoor activities for the next day.
When 1-hour PM2.5 levels are raised, healthy people are advised to reduce strenuous outdoor activity for the next hour, while elders, pregnant women, children and people with chronic heart or lung conditions should avoid such activity.
In an update on Monday, NEA said clusters of scattered hotspots were detected in the southern parts of Sumatra and the southern parts of Kalimantan, while isolated hotspots were detected in parts of Java, Sulawesi and the Lesser Sunda Islands.
Moderate to dense smoke plumes were seen over southern Sumatra, drifting northwards towards parts of Peninsular Malaysia and Singapore.
Moderate to dense smoke haze was also observed over parts of Kalimantan.
Dry weather is expected to continue over most parts of the southern Southeast Asian region except for showers forecast over the northern parts of Sumatra, Borneo and Peninsular Malaysia, the agency said.
The hotspot and haze situation is expected to remain escalated, with a continued risk of transboundary haze.
The deterioration in Singapore's air quality had been anticipated. NEA said on Sunday that the 24-hour PSI for Monday was forecast to be in the high end of the moderate range to the low end of the unhealthy range.
The 24-hour PSI is Singapore's indicator of daily air quality and forms the basis of NEA's daily health advisories. It is calculated using six air pollutants - PM2.5, PM10, ozone, sulphur dioxide, nitrogen dioxide and carbon monoxide - and reflects the average air quality of the past 24 hours.
The 1-hour PM2.5 reading, on the other hand, is the hourly average of the PM2.5 pollutant levels. PM2.5 is fine particulate matter with a diameter of 2.5 micrometres or shorter, and is the dominant pollutant during haze that causes harm to health.
A 24-hour PSI reading is considered "unhealthy" when it is in the 101 to 200 range, "very unhealthy" when it is within the 201-300 range and "hazardous" when it goes over 300.
The hourly PM2.5 reading is classified in four bands: normal, elevated, high and very high. It is considered elevated when it ranges from 56 to 150. The "high" band ranges from 151 to 250, and readings above that are classified as "very high".
