Haze update for Sept 15: PSI expected to remain in high moderate to mid-unhealthy range
Air quality in Singapore improved slightly on Tuesday (Sept 15), a day after the 24-hour Pollutant Standards Index (PSI) slipped into the unhealthy range in all five regions in Singapore.At 6pm, the 24-hour PSI ranged between 92 and 131, placing Singapore's overall air quality in the moderate to unhealthy range.The highest reading of 131 was recorded in central Singapore, followed by the western (114) and eastern (113) regions. Both northern (93) and southern (92) Singapore remained in the moderate range.Meanwhile, the one-hour PM2.5 concentration readings ranged between 43 and 74 — with only the southern region in the normal band — while the four remaining regions recorded readings in the elevated band.The country's 24-hour PSI forecast is again expected to be in the high moderate to mid-unhealthy range over the next 24 hours.