PM2.5 levels elevated in four regions; 24-hour PSI in unhealthy range across most of Singapore
As of 11pm, the 1-hour PM2.5 reading was highest in central Singapore at 81.
A woman is seen wearing a mask in central Bishan during hazy conditions on the evening of Oct 5, 2026. (Photo: CNA/Marcus Mark Ramos)
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SINGAPORE: PM2.5 levels rose across Singapore on Tuesday (Oct 6), with 1-hour readings in the elevated band in most regions.
As of 11pm, the 1-hour PM2.5 reading was the highest in central Singapore at 81. The readings, which provide a more current indication of air quality, were 76 in the west, 61 in the east, 29 in the south and 59 in the north.
The 24-hour Pollutant Standards Index (PSI) was in the unhealthy range in three regions, with the south remaining in the moderate range as of 11pm. The north dropped into the moderate range at 11pm.
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 24 hours.
When 1-hour PM2.5 levels are elevated, healthy people are advised to reduce strenuous outdoor activity for the next hour, while the elderly, pregnant women, children and people with chronic heart or lung conditions should avoid such activity.
In its haze advisory on Tuesday evening, NEA said the 24hr-PSI was expected to be in the high moderate to mild unhealthy range for the next 24 hours.
The agency earlier said that scattered hotspots were detected in Kalimantan and Sumatra, while a few hotspots were detected elsewhere in the southern part of Southeast Asia.
"Moderate to dense smoke plumes from southern Sumatra and West Kalimantan were observed drifting towards Singapore," NEA said in its evening advisory.
With dry weather forecast to persist over Kalimantan as well as southern and central Sumatra, and prevailing east-southeasterly to southeasterly winds, the haze is likely to continue drifting to Singapore, it said.
NEA had said earlier that the hotspot and haze situation may improve in areas experiencing showers. But they could continue to stay elevated in areas experiencing prolonged periods of dry weather, with a continued risk of transboundary haze occurrence, it added.
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".
