Singapore’s west records season-high PSI of 230 as haze enters 14th day

The Pollutant Standards Index, or PSI, is a single measure that summarizes six key air pollutants. It uses a 24-hour rolling average, making it useful for showing broader air-quality conditions over time. The scale matters because higher readings signal greater pollution and more serious public-health concerns.

A PSI reading of 230 falls within the 201–300 range. That range is classified as “very unhealthy.” At 10am, western Singapore recorded 230, the highest reading reported in the article. The rest of the island recorded readings from 130 to 187, placing those areas in the “unhealthy” category.

This reading showed that pollution was especially severe in the west, while unhealthy air affected the entire island. Singapore had already experienced 14 consecutive days of unhealthy air. The NEA forecast a PSI between 150 and 220, meaning conditions could remain unhealthy or very unhealthy.

The haze was widespread because every Singapore region recorded elevated one-hour PM2.5 at 10am. The PSI showed island-wide unhealthy air, with readings from 130 to 187 outside the west. Western Singapore was more severely affected, reaching 230 and entering the “very unhealthy” category.

The regional PM2.5 figures show the uneven intensity. Readings were 72 in the north, 82 in the south, 71 in the east, 139 in the west and 117 in the central region. Under the article’s scale, 56 to 150 indicates elevated concentrations. The west therefore had the highest one-hour PM2.5, while all regions were elevated.

This combination meant the haze was not limited to one neighbourhood. Singapore had endured 14 consecutive days of unhealthy air since October 5. The highest PM2.5 reading of the year, 288, was recorded in the west on October 14, classifying it as very high.

One-hour PM2.5 and the PSI are not measuring exactly the same thing. PM2.5 records fine particulate matter in micrograms per cubic metre over one hour. It shows how concentrated these tiny particles are at a recent point in time. The PSI combines six pollutants and uses a 24-hour rolling average.

For example, western Singapore had a one-hour PM2.5 reading of 139 at 10am and a PSI of 230. The PM2.5 figure described the recent concentration of fine particles. The PSI reflected pollution accumulated across the previous 24 hours and included other pollutants as well. A short-term spike or dip can therefore appear differently in each measure.

Together, the readings provide a fuller picture. One-hour PM2.5 can show immediate changes, while the PSI indicates sustained overall conditions. In this episode, both pointed to serious pollution, although they used different averaging periods, pollutants and classification scales.

The article focuses on measurements and forecasts, not medical symptoms. Based on established health guidance, prolonged exposure to unhealthy or very unhealthy air can cause eye, nose and throat irritation, coughing, wheezing and shortness of breath. Fine particles can penetrate deep into the lungs, making sustained exposure more concerning than a brief episode.

People with asthma or other lung disease may experience worsened symptoms. Older adults, children and people with heart or respiratory conditions can be more vulnerable. Healthy people may also notice breathing discomfort or reduced tolerance for strenuous outdoor activity when pollution remains high. These effects are general health knowledge, not specific cases reported in the article.

The conditions described were persistent. Singapore had 14 consecutive days of unhealthy air, and the west reached a PSI of 230. That duration matters because repeated exposure can prolong irritation and aggravate existing illness. The article records the risk conditions, but it does not report health outcomes.

Smoke haze reaching Singapore can come from both Sumatra and Kalimantan, according to the article. The haze is therefore not necessarily produced over Singapore itself. Regional weather matters because winds can move smoke across the surrounding seas and toward the island.

The article gives a direct example. Winds were forecast to shift from the south-south-east or south, potentially reducing smoke-haze transport from Kalimantan. At the same time, some smoke haze from Sumatra could drift toward Singapore. This shows how wind direction can reduce one pathway while allowing another to remain active.

Conditions could change again as winds gradually weakened and blew from the south-east or south. That pattern was expected to further reduce movement from Kalimantan, while not guaranteeing clear air. The article does not explain how the smoke was produced; it identifies the two regional sources and the winds that carry it.

Rain can temporarily improve air quality by washing some suspended particles from the atmosphere and by stopping or reducing their movement near the ground. Wind changes can also alter where smoke travels. These are established atmospheric effects; the article reports the forecast conditions but does not explain the physical process in detail.

On October 18, showers were expected across Singapore and the surrounding region, potentially offering relief. Winds were forecast to shift toward the south-south-east or south. That change could reduce the transport of smoke haze from Kalimantan toward Singapore. However, the same weather pattern could still allow some haze from Sumatra to drift toward the island.

More showers were forecast over Singapore and parts of Kalimantan on October 19 and 20. Winds were also expected to weaken gradually and blow from the south-east or south. These developments could further reduce haze movement from Kalimantan, but they did not guarantee immediate or complete clearance.

The article does not explain why haze crises recur. Established regional knowledge links recurring episodes to widespread fires, often during drier conditions, while seasonal winds carry smoke across national borders. This broader explanation goes beyond the article’s stated facts. The article itself identifies smoke haze from Sumatra and Kalimantan and describes wind patterns affecting its movement.

The current episode was similar to the 2015 crisis in duration. Singapore experienced continuous unhealthy air from October 5, reaching 14 consecutive days. In 2015, the country endured 14 consecutive days of bad air from September 23 to October 7. The article describes the current stretch as Singapore’s longest period of poor air quality since that crisis.

The severity also varied by location this time. The west reached a PSI of 230, or very unhealthy, while other regions remained unhealthy. Forecast showers and changing winds offered possible relief, but Sumatra haze could still drift toward Singapore.