air quality in Singapore<\/span><\/a> improved in the morning of Oct 25, with the hourly PM2.5 readings returning to \u201cnormal\u201d for three regions, even as the 24-hour PSI levels remained in the \u201cunhealthy\u201d band across the island.<\/p>\nAt 7am, the PM2.5 readings were in the \u201cnormal\u201d range in the north (55), south (44) and central (54), while the eastern and western regions remained in the \u201celevated\u201d band at 61 and 62, respectively.<\/p>\n
PM2.5 readings are gauged hourly and reflect the current air quality. Scores from zero to 55 represent normal values, those between 56 and 150 indicate an elevated concentration of fine particles.<\/p>\n
Meanwhile, the 24-hour Pollutant Standards Index (PSI) stood in the unhealthy range across the island: 111 in the north, 104 in the south, 112 in the east, 140 in the west and 115 in the central region.<\/p>\n
Air quality is considered good to moderate when the PSI \u2013 a 24-hour rolling average of six key air pollutants \u2013 is in the range of 0 to 100, and unhealthy when it is in the range of 101 to 200.<\/p>\n