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SINGAPORE \u2013 The air quality across most of Singapore remained in the unhealthy range early on Oct 6, with the north (107), east (112), west (117) and central (130) regions all above the 101 threshold at 6am on the 24-hour Pollutant Standards Index (PSI).<\/p>\n
Only the south (95) remained in the moderate range.<\/p>\n
Air quality is considered unhealthy when the PSI \u2013 a 24-hour rolling average of six key air pollutants and used in planning for outdoor activities the next day \u2013 is in the range of 101 to 200.<\/p>\n
PM2.5 readings, which are used as a gauge for immediate activities, were elevated in three of the five regions \u2013 the east (56), west (59) and central (60).<\/p>\n
The PM2.5 remained at the normal levels in the south (35) and in the north (48).<\/p>\n
An hourly PM2.5 reading between 56 and 150 indicates an elevated concentration of fine particles.<\/p>\n
Between 9pm and midnight on Oct 4, the entire island was shrouded in unhealthy air, with the peak being a 136 reading on the PSI at midnight in the central region. The central and west regions are the only two regions to lie in the unhealthy range for at least 24 hours.<\/p>\n