SINGAPORE – The air quality across the island remained poor early on Oct 18, with the 24-hour PSI continuing to lie in the unhealthy range islandwide, except in the west, where the reading of 228 put it in the “very unhealthy” band.
At 7am on Oct 18, the PSI readings in the other regions stood at 129 in the north, 173 in the south, 180 in the east and 185 in the central region.
Air quality is considered “unhealthy” when the PSI – a 24-hour rolling average of six key air pollutants – is in the range of 101 to 200, and “very unhealthy” when it is in the range of 201 to 300.
The one-hour PM2.5 readings – measured in micrograms per cubic metre – were all in the elevated range at 7am on Oct 18: north (78), south (99), east (103), west (125) and central (124).
PM2.5 scores from 0 to 55 represent normal values, those between 56 and 150 indicate an elevated concentration of fine particles, while readings between 151 and 250 are considered high and scores above 251 are classified as very high.
The highest PSI reading this haze season – 229 – was recorded from 3pm to 4pm in the central region on Oct 16.
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