Singapore air quality remains in moderate range

SINGAPORE: Air quality across Singapore remained in the moderate range on Sunday (Sep 6).This comes a day after conditions improved to the moderate range, following 24-hour Pollutant Standards Index (PSI) readings in three regions reaching the unhealthy range.As of 7pm on Sunday, the 24-hour PSI was between 72 and 87, in the moderate range, according to the National Environment Agency (NEA).In its daily haze situation update issued at 6pm, NEA said fair and windy conditions occurred over Singapore on Sunday. Amid the ongoing dry conditions, moderate to dense smoke plumes from fires in southern and central Sumatra, as well as West Kalimantan, continued to drift towards Singapore, the agency said.While some showers are forecast over Kalimantan, dry conditions are expected over Singapore and the surrounding region in the coming days.With prevailing winds blowing from the southeast or south, there remains a risk of haze affecting Singapore should the fires persist.NEA forecast the 24-hour PSI for Singapore to be in the high-moderate to low-unhealthy range over the 24 hours from 6pm.The 24-hour PSI in the central region entered the unhealthy band of 101 to 200 at 7am on Friday, marking the first time the PSI had exceeded 100 since Oct 8, 2023.This led NEA to start issuing daily haze advisories, including a 24-hour PSI forecast, to help the public plan activities and events for the following day.The PSI would later also cross into the unhealthy range in both eastern and western Singapore.The 24-hour PSI is Singapore's indicator of daily air quality and forms the basis of NEA's daily health advisories. It is calculated using six air pollutants: PM2.5, PM10, ozone, sulphur dioxide, nitrogen dioxide and carbon monoxide. The one-hour PM2.5 reading measures the hourly average concentration of fine particulate matter, the dominant pollutant during haze episodes.While the 24-hour PSI is an average of the past 24 hours, the one-hour PM2.5 reading reflects the air quality at a single point in time.A 24-hour PSI reading is considered "very unhealthy" when it is within the 201 to 300 range and "hazardous" when it goes over 300.