SINGAPORE: Air quality across Singapore improved on Thursday (Oct 22), with hourly PM2.5 readings falling within the normal range in all regions as of 8am.
The western region was the last to return to the normal band at midnight, joining the other four regions. Hourly PM2.5 readings ranged from 22 to 42.
At 8am, the 24-hour Pollutant Standards Index (PSI) remained unhealthy in western Singapore with a reading of 108. Readings in the other four regions remained moderate, ranging from 74 to 95.
The National Environment Agency (NEA) earlier forecast unhealthy air quality for Thursday as smoke haze from Kalimantan could drift towards Singapore, before a wind shift could bring haze from Sumatra over the weekend.
On Monday, Singapore saw a brief improvement in air quality when PSI readings fell into the moderate range in three of the country's five regions for the first time in more than a week.
Before Monday, the last time Singapore recorded moderate air quality was on Oct 9.
ADVICE FOR VULNERABLE GROUPS
When the 24-hour PSI is in the unhealthy range, NEA advises the elderly, pregnant women and children to minimise prolonged or strenuous outdoor physical exertion.
People with chronic diseases, including heart or lung conditions, should avoid such activities.
For decisions on mask use and immediate outdoor activities, the public should refer to the one-hour PM2.5 readings instead.
When the 1-hour PM2.5 readings are in the high band, vulnerable individuals, including the elderly, pregnant women and those with chronic heart or lung conditions, should avoid outdoor activities, according to the Ministry of Health (MOH).
Those who need to go outdoors for immediate activities may wear a well-fitting N95 mask or equivalent to reduce their exposure to haze particles.
When 1-hour PM2.5 readings reach the very high band of 251 and above, healthy individuals should also minimise all outdoor activities. Those who need to venture outdoors may similarly use an N95 mask for protection.
However, MOH said N95 masks are generally not needed for commuting between home and school or work, or in indoor environments.
The ministry has also advised the elderly, pregnant women and those with severe heart or lung conditions who experience breathing difficulties to consult their doctor before using an N95 mask.
Those who experience discomfort while wearing one should take a break from using it.
Besides N95 masks, KN95, FFP2 and KF94 masks are also effective in reducing exposure to haze particles, according to MOH.
Members of the public can visit the HazeMaskGoWhere website for more information on collection locations and live updates on mask availability at the vending machines.
MOH had also issued guidance on Oct 13 on the types of masks that can be used for protection against haze.
It said surgical masks can help reduce discomfort and the risk of infections by providing a barrier against larger irritant particles.
However, if PM2.5 readings are above 250 and people need to be outdoors for several hours, MOH recommends wearing an N95 or equivalent mask.
Cloth masks generally do not filter fine particles effectively, although they can reduce discomfort by blocking larger irritant particles in the air.