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SINGAPORE \u2013 The air quality in parts of Singapore dipped back into the unhealthy range again early on Oct 5, with the 24-hour PSI reading at 6am in the central region standing at 110 and the west at 102.<\/p>\n
PM2.5 readings, which are used as a gauge for immediate activities, were elevated in two of the five regions across Singapore.<\/p>\n
The PM2.5 stood at 93 in the central region, and 81 in the west. Readings in north, south, and east were in the normal band, ranging from 49 to 52.<\/p>\n
Air quality is considered unhealthy when the 24-hour PSI is in the range of 101 to 200, while an hourly PM2.5 reading between 56 and 150 indicates an elevated concentration of fine particles.<\/p>\n
The PSI \u2013 a 24-hour rolling average of six key air pollutants and used in planning for outdoor activities the next day \u2013 had fluctuated between the moderate and unhealthy range on Oct 4.<\/p>\n
It hit a high of 103 at about 3am before falling back to into the 90s where it spent much of the day till 9pm, when it moved briefly into the unhealthy range at 101 before dipping back to 99 at 11pm.<\/p>\n
It began its upward trajectory at midnight, moving up to 100 and climbing slowly overnight.<\/p>\n