Singapore experienced a modest improvement in air quality from the previous night through Wednesday (Oct 21), though 1-hour PM2.5 readings were elevated in the western and central regions as of 9am.

In the central region, 1-hour PM2.5 levels fluctuated throughout the night, dropping into the normal band at 3am and climbing again at 7am. In the eastern region, the reading entered the elevated band at 6am before returning to normal by 7am.

Across all five regions, 1-hour PM2.5 readings ranged between 41 and 81.

As of 9am, the 24-hour Pollutant Standards Index (PSI) remained in the unhealthy range in the west and central areas, registering 132 and 116 respectively.

Readings in the remaining regions ranged from 83 to 97.

The 24-hour PSI in the east improved to the moderate range at 3am, joining the south, where readings had returned to moderate levels at 10pm on Tuesday.

Air Quality Expected to Stay Unhealthy

The National Environment Agency (NEA) stated on Tuesday evening that Singapore's air quality is forecast to remain unhealthy on Wednesday, with the PSI expected to range from 110 to 180.

Although showers are anticipated over Singapore and the surrounding region, smoke haze from fires in Kalimantan may still be carried towards Singapore as winds are forecast to blow from the east-southeast to southeast.

Dry conditions are also expected to persist over southern Kalimantan in the coming days, with prevailing winds potentially bringing more smoke haze towards Singapore.

On Tuesday afternoon, showers were observed in parts of Singapore and the surrounding region. However, residual smoke haze from Kalimantan was seen drifting towards Singapore, while smoke haze was also detected in Sumatra.

Singapore saw a brief improvement in air quality on Monday, when PSI readings fell into the moderate range in three of the country's five regions for the first time in over a week.

Prior to Monday, the last occasion Singapore recorded moderate air quality was on Oct 9.

Guidance 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.

Individuals with chronic diseases, including heart or lung conditions, should avoid such activities.

For decisions regarding mask use and immediate outdoor activities, the public should refer to the one-hour PM2.5 readings instead.

When 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.