Rising haze risks: What the PSI in Singapore means for your outdoor plans

With dry conditions expected to keep the regional hotspot and haze situation elevated in the coming days, here is how to decide whether to go ahead with outdoor plans.

Residents in Singapore should keep a closer watch on air-quality readings before heading outdoors, as dry conditions in parts of the region are expected to sustain an elevated risk of transboundary haze in the coming days.

According to the National Environment Agency on 4 September (Friday), Central Singapore recorded a 24-hour Pollutant Standards Index (PSI) reading of 104 at 9am on Friday, placing it in the unhealthy range. The nationwide PSI reading was 78, in the moderate range.

Readings differed across the island: the West recorded 89, the East 88, the North 78 and the South 75.

At the same time, the islandwide one-hour PM2.5 reading stood at 44 micrograms per cubic metre, which is in the normal band. The regional readings ranged from 37 in the South to 67 in central Singapore, which was in the elevated band.

The differing readings highlight why people should use the appropriate measure when deciding whether to exercise, work or spend time outdoors.

Going out now? Check the one-hour PM2.5 reading

• At readings in the normal band, from 0 to 55 micrograms per cubic metre, people can continue with their usual activities.
• When readings enter the elevated band, from 56 to 150 micrograms per cubic metre, the public should reduce strenuous outdoor activity. Vulnerable people should avoid strenuous outdoor activity.
• At high readings of 151 to 250 micrograms per cubic metre, the public should avoid strenuous outdoor activity, while vulnerable people should avoid outdoor activity.
• When the reading reaches the very high band of at least 251 micrograms per cubic metre, all outdoor activity should be minimised. Vulnerable people should avoid outdoor activity.

Planning for tomorrow? Look at the 24-hour PSI forecast

• A PSI reading of 0 to 50 is considered good, while 51 to 100 is moderate. Normal activities may continue at these levels.
• At an unhealthy PSI reading of 101 to 200, healthy people should reduce prolonged or strenuous outdoor physical exertion. Elderly people, pregnant women and children should minimise such activity, while people with chronic heart or lung disease should avoid prolonged or strenuous exertion.
• The advice becomes more stringent as readings rise into the very unhealthy and hazardous ranges.
  • People who are elderly, pregnant, young children, or have chronic heart or lung conditions are considered more vulnerable to the effects of haze.
  • They should take extra precautions when air quality worsens and seek medical attention if they feel unwell.
• Residents can monitor the latest official one-hour PM2.5 readings before immediate outdoor activity, and consult the 24-hour PSI forecast when making plans for the next day.

Over the next few days, dry conditions are forecast to continue over many parts of the southern ASEAN region. The hotspot and smoke-haze situation is expected to remain elevated in fire-prone areas experiencing prolonged dry weather, with a continued risk of severe transboundary haze.

READ MORE: Employers urged to prepare haze protection measures for workers as Singapore monitors air quality 

Lead image and infographics / NEA