Smoke blown from a hot spot in Johor caused slightly hazy conditions with a burning smell in parts of Singapore yesterday morning, said the National Environment Agency (NEA).
The hot spot was detected in Johor in the late afternoon on Monday. The smoke plume was blown by the prevailing north-easterly winds towards Singapore before it dissipated later that evening.
But with prevailing winds expected to continue blowing from the north to north-east over these few days, residents may still have detected similar conditions over parts of Singapore yesterday, said the NEA in a Facebook post.
The hourly concentration of fine particulate matter (PM2.5) yesterday entered Band 2 (Elevated) between 6am and 7am in the east of Singapore, before returning to Band 1 (Normal) from 8am.
During periods of haze caused by forest fires in the region, the dominant pollutant is PM2.5.
As at 11am yesterday, the 24-hour Pollutant Standards Index (PSI) was 61-74, in the moderate range.
The hourly PM2.5 readings are normal when the concentrations are between 0 and 55 micrograms per cubic m of air. The readings reach elevated levels when the concentrations are between 56 and 150 micrograms per cubic m.
During the elevated levels, people are advised to reduce strenuous outdoor activity, while vulnerable individuals such as the elderly, pregnant women and children are advised to avoid strenuous activity until the concentrations return to normal levels.
The NEA said it will continue to monitor the situation and provide updates when necessary.
Those deciding whether or not to go ahead with outdoor activities can refer to the one-hour PM2.5 concentration readings and health advisory at www.haze.gov.sg
Last Saturday, Singapore's air quality in the north hit unhealthy levels for three hours because of higher levels of a pollutant known as ozone, and not because of transboundary haze.
The PSI reading in the north hit 102 at 7pm that day. It climbed to a peak of 108 at 8pm, before dropping to 90 at 10pm, which was within moderate levels.
