SINGAPORE - The number of hot spots detected in Kalimantan, Indonesia, on Wednesday (Sept 11) has more than doubled, according to the National Environment Agency (NEA).

And as Sumatra and Kalimantan are expected to continue having dry weather, the haze situation is likely to persist in Singapore, said the agency.

The Republic may continue to experience hazy conditions on occasion, said NEA, noting that there was a slight haze in Singapore on Wednesday morning.

A total of 1,584 hot spots were detected in Kalimantan, up from the 749 hot spots detected on Tuesday, said the agency.

More than 600 hot spots were detected in Sumatra, mostly in the provinces of Riau, Jambi and South Sumatra.

Haze was observed over many areas in Kalimantan, and some haze had also spread to an adjacent area in the South China Sea.

Areas in peninsular Malaysia were also affected by smoke haze which had blown in with the prevailing winds.

In Singapore, the prevailing winds are expected to blow from the south or south-east for the rest of Wednesday.

NEA said that as of 6pm on Wednesday, the 24-hour Pollutant Standards Index (PSI) was between 69 and 75, in the moderate range.

The one-hour PM2.5 concentration readings were in the normal range.

PM2.5 is a measure of the concentration of tiny particles less than 2.5 micrometres in diameter - or about one-thirtieth the diameter of a human hair - in the air.

When the PM2.5 reading is in the elevated range, which is above the normal range, haze particles can affect the heart and lungs, especially in people who have chronic heart or lung conditions like asthma. Those with such chronic conditions should ensure that their medication is on hand and readily available.

For the next 24 hours, the one-hour PM2.5 concentration readings are expected to range between the normal and elevated bands, and the 24-hour PSI is forecast to be in the moderate range.

NEA said it is monitoring the situation closely and will provide further updates when necessary. Regular updates on the haze situation can be found on NEA's website at www.nea.gov.sg

"Given the air quality forecast for the next 24 hours, everyone can continue with normal activities," said NEA.

People who are not feeling well, especially the elderly and children, and those with chronic heart or lung conditions, should seek medical attention, the agency advised.