SINGAPORE – Air quality hovered around the unhealthy level for most of today (Sept 18), with the three-hour Pollutant Standard Index (PSI) entering into the unhealthy range once in the morning and for a few hours in the afternoon.

The three-hour PSI reading was above 90 throughout the day, reaching 102 at 10am before dipping out of the unhealthy level. From 2pm, the three-hour PSI climbed steadily from 100 to reach 106 at 4pm, before falling back into the moderate range with a reading of 95 at 6pm.

The 24-hour PSI reading at 6pm was 95-99. An hour before it was 96-102. Air quality is in the moderate range when the PSI value is between 51 and 100, and is considered unhealthy when the PSI value is between 101 and 200.

Source: www.haze.gov.sg

The National Environment Agency (NEA) said that the hazy conditions today were caused by transboundary haze from Kalimantan, with the prevailing winds blowing from the east or south-east. "Based on NOAA satellite data, there is widespread thick smoke haze in the southern parts of Kalimantan, which is also spreading to the southern parts of the South China Sea," said the NEA in its haze update.

"These hazy conditions in Singapore may be sustained over the next one to two days, as Kalimantan is expected to experience mostly dry conditions, and winds continue to blow from east or south-east," the agency added.

Minister for the Environment and Water Resources Vivian Balakrishnan has written to the Indonesia Minister of Environment Balthasar Kambuaya to express Singapore’s "deep concern over the transboundary haze from Indonesia that has affected Singapore", said the NEA.  He also reiterated Singapore’s offer of assistance to the Indonesians to help deal with the fires.

Source: Dr Balakrishnan's Facebook page

The NEA said haziness may be experienced during the day tomorrow. The overall air quality for the next 24 hours is expected to fluctuate between the high-end of the Moderate range and the low-end of the Unhealthy range. Prevailing winds are expected to blow from the east or south-east, and thundery showers are forecast in the afternoon for Singapore. 

Last night, the three-hour PSI tipped into the unhealthy range at 102 at 8pm after staying in the moderate range for most of the day.

Earlier this week, the NEA said that Singapore is expected to experience haze for the next two weeks due to prevailing wind conditions from the south-southeast or the south-west where Sumatra lies, with periods of consecutive dry days that are typical during this South-west Monsoon season.