20 June 2013 17:45 | By Alyssa Woo
Clearing the air on the haze situation

How is the PSI measured?



Clearing the fog on the haze (© ASSOCIATED PRESS)
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  • Clearing the fog on the haze (© EDGAR SU/Newscom/RTR)
  • Clearing the fog on the haze (© ASSOCIATED PRESS)
  • Clearing the fog on the haze (© EDGAR SU/Newscom/RTR)
  • Clearing the fog on the haze (© ASSOCIATED PRESS)
  • Clearing the fog on the haze (© STRINGER/INDONESIA/Newscom/RTR)
  • Clearing the fog on the haze (© EDGAR SU/Newscom/RTR)
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How is the PSI measured?

The Particulate Matter (PM) measures the concentration of 5 major pollutants (atmospheric particles, ozone, nitrogen dioxide, sulphur dioxide and carbon monoxide), which is then used to get readings for the PSI and Air Pollution Index (API).

In the past few days, there has been confusion over the PSI readings on the National Environment Agency of Singapore's (NEA) website, where both 24-hr and 3-hr average readings are listed. So a 3-hour PSI reading of, say 226, indicates the average reading in the past three hours and is not necessarily a gauge of the haze situation in real-time.

Residents in Singapore may access these readings at the NEA website (http://www.nea.gov.sg/psi/), while those in Malaysia can do so at http://www.doe.gov.my/apims/.

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