Since the early hours of Saturday (Aug. 27), Pollutant Standards Index (PSI) levels in most parts of Singapore has entered the "unhealthy" range.

Air quality is considered unhealthy when they enter PSI range 101-200. PSI readings of 51-100 are considered moderate.

PM2.5 readings are also rising steadily. The northern part of Singapore had the highest one-hour PM2.5 reading of 94, as of 10am.

PM2.5 is a fine particle that is the dominant pollutant during the haze season. As the one-hour PM2.5 readings are the average of PM2.5 concentrations over an hour, it can be used as an indicator to plan for immediate activities.

The hazy conditions are expected to persist throughout today, and the PSI for the next 24-hours is expected to remain at the unhealthy level, while PM2.5 levels are forecast to fluctuate between "elevated" and "high" ranges.

This is a development from an update several hours prior that PSI levels for the coming 12 hours are likely to remain in the high end of the “moderate” range.

The National Environment Agency (NEA) has issued a health advisory stating that the elderly, pregnant women and children should reduce prolonged or vigorous outdoor activities. Persons with lung and heart conditions are advised to stay indoors and stop all strenuous outdoor activities.

Those who feel unwell under hazy conditions, especially those with chronic heart or lung conditions, should seek medical attention.

Since Aug. 26,  NEA has been providing the public with updates on the haze situation. In the latest post on its Facebook page, NEA said that a "total of 11 hotspots were detected in Sumatra," and that moderate to dense smoke haze was moving towards Singapore.

The hazy conditions could worsen should denser haze be blown in from Sumatra by westerly winds.

NEA has contacted their Indonesian counterparts to "register Singapore’s concerns over additional episodes of deterioration in air quality in Singapore should the fires continue."

They also urged Indonesia to control the breakout of fires, and requested for an updated situation in Sumatra and Kalimantan.

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