SINGAPORE: After a day of air quality in the unhealthy range, there was an improvement in the Pollutant Standards Index (PSI) on Thursday (Sep 19).
Readings fell gradually throughout the day, and at 9pm, the 24-hours PSI entered the moderate range in all areas.
The readings were, as of 9pm:
- 88 in the north
- 92 in the east
- 98 in the south
- 93 in the west
- 88 in the central region
According to the National Environment Agency (NEA), PSI readings of 50 and below denote “good” air quality, “moderate” for 51-100 and “unhealthy” for 101-200.
The improved air quality was due to "a strengthening of winds blowing from the southeast", which helped disperse the smoke haze from Singapore, said NEA in a media advisory on Thursday.
READ: Understand the haze: What do Singapore's air quality readings mean and how do they differ from others?
The one-hour PM2.5 reading at 9pm ranged between 18-28µg/m3, which is in the normal band.
PM2.5 is a measure of tiny particles less than 2.5 micrometres in diameter in the air. When the PM2.5 reading is in the elevated range, haze particles can affect the heart and lungs, especially in people who have chronic heart or lung conditions.
According to NEA, one-hour PM2.5 readings are a "good indicator of current air quality", and can be used for those deciding whether to go for immediate outdoor activities, such as a jog.
A total of 196 hotspots were detected mostly in Riau, Jambi, South Sumatra and Lampung provinces of Indonesia, said NEA, down from 238 on Wednesday.
For the rest of the day, slightly hazy conditions are expected, the agency added.
The 24-hr PSI is forecast to be between the high end of the moderate range and low end of the unhealthy range.
As for the one-hour PM2.5 readings over the next 24 hours, they are expected to remain in the normal range, and may enter the elevated range if haze from the surrounding region is blown in.
The haze has also affected neighbouring Malaysia, with air quality remaining at "unhealthy" or "very unhealthy" levels in most of the country on Thursday. Nearly 2,500 schools were closed, affecting 1.7 million students.
The haze originated from peat and forest fires in Indonesia, where many still practise the slash-and-burn agricultural methods.
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