\n<\/p>\n
SINGAPORE \u2013 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 \u201cvery unhealthy\u201d band.\u00a0\u00a0\u00a0<\/p>\n
At 7am\u00a0on Oct 18,\u00a0the PSI readings in the other regions stood at 129\u00a0in the north, 173 in the south, 180 in the east and 185 in the central region.<\/p>\n
Air quality is considered \u201cunhealthy\u201d when the PSI \u2013 a 24-hour rolling average of six key air pollutants \u2013 is in the range of 101 to 200, and \u201cvery unhealthy\u201d when it is in the range of 201 to 300.<\/p>\n
The one-hour PM2.5 readings \u2013 measured in micrograms per cubic metre \u2013 were all\u00a0in the elevated range at 7am on Oct 18: north (78), south (99), east (103), west (125) and central (124).<\/p>\n
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.<\/p>\n