SINGAPORE - Singapore may experience occasional slightly hazy conditions as the number of hot spots detected in Sumatra soared from 113 last Saturday (Sept 7) to 333 on Sunday, the National Environment Agency (NEA) said.

This is because winds are forecast to continue blowing from the south-east or south and may blow smoke haze from these hot spots in Indonesia to the Strait of Malacca.

The NEA however predicted "generally fair conditions" for Singapore over the next few days and will provide updates when necessary on its website.

As of 10am on Monday, the 24-hour Pollutant Standards Index (PSI) was between 71 and 79, in the moderate range of the index. This was an increase from the 63 to 69 reading recorded at 6pm yesterday.

The PM2.5 level at 10am on Monday was between 24 and 30, in band I (normal) of the PM2.5 scale. The NEA said PM2.5 concentration readings are a good indicator of current air quality, and those concerned should use them to decide on whether to go for immediate outdoor activities, such as a jog.

PM2.5 readings measure 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.

In addition to PSI levels, the NEA said that the health impact of haze is also dependent on one's health status and the length and intensity of outdoor activity. Those who are not feeling well, especially the elderly and children, and those with chronic heart or lung conditions, should seek medical attention.

The NEA website www.nea.gov.sg will provide regular updates on the haze situation.