24-hour PSI returns to moderate range in northern, southern Singapore; 1-hour PM2.5 elevated in 3 regions
Air quality in Singapore has improved, with 24-hour Pollutant Standards Index (PSI) readings in the northern and southern regions returning to the moderate range on Tuesday (Sept 15) afternoon.Northern Singapore recorded unhealthy air quality for 10 hours, from 1am on Tuesday, before returning to the moderate range at 10am. The southern region spent 14 hours in the unhealthy range before improving to moderate levels at 11am.At 3pm, data from the National Environment Agency (NEA) showed that PSI readings ranged from 92 to 135, placing air quality in the moderate to unhealthy bands. Central Singapore recorded the highest PSI reading at 135, followed by the western (118) and eastern (115) regions.Meanwhile, the one-hour PM2.5 reading, an indicator of fine particulate matter in the air and a measure of current air quality, ranged from 48 to 101 at 3pm.A reading of between 0 and 55 µg/m3 falls within the normal band, while readings ranging from 56 to 150 are classified as within the elevated band. All three regions with moderate air quality — central (101), western (71) and eastern (70) Singapore — also recorded elevated PM2.5 readings.