SINGAPORE — The three-hour Pollutant Standards Index (PSI) reading was at 310 at 6pm today (June 20), according to the National Environment Agency (NEA).
Last night saw the PSI hit an all-time high of 321 at 10pm, but that was surpassed at 1pm when the PSI hit 371.
The three-hour PSI readings are calculated based on PM10 concentrations only.
The PSI index was developed by the United States’ Environmental Protection Agency (EPA) to provide accurate and timely information about daily levels of air pollution. Air pollutants such as sulphur dioxide, nitrogen dioxide, ozone, carbon monoxide and particulate matter called PM10 (particulate matter of 10 microns or smaller in size) are used in the determination of the index.
The NEA’s 24-hour PSI reading as of 12pm is 169-196, while the 24-hour PM2,5 reading as of 12pm is 232-291.
The PM2.5 reading measures fine particles measuring 2.5 micrometres or less in diameter, as well as ultrafine particles, and soot.
PSI Air quality descriptor
0-50: Good
51-100: Moderate
101-200: Unhealthy
201-300: Very unhealthy
+300: Hazardous
Source: http://tdy.sg/neapsi
More about the PSI: http://tdy.sg/PSIhowandwhy
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