Pollutant Standard Index (PSI)

Pollutant Standard Index


We are sure many Singaporeans or those living in Singapore have heard of the term PSI, especially during June period in regular years. This PSI comes out as a hot topic regularly whenever we are hit by the smoke haze which is mainly due to forest fire in nearby Sumatra, Indonesia.
PSI also known as Pollution Standards Index is a type of air quality index which is a number used to indicate the level of pollutants in the air.
Besides Singapore, some other countries also use air quality indexes. However, the calculations used to derive air quality indices may differ. Different countries also use different names for their indices such as Air Quality Health Index, Air Pollution Index and Pollutant Standards Index.


The PSI was based on five pollutants but Singapore has included fine particulate matter (PM2.5) as the sixth pollutant since 2014. The 6 unwanted air molecules are: sulphur dioxide (SO2), particulate matter (PM10), nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3) and fine particulate matter (PM2.5).


We have a unique PSI table that is grouped by index values and descriptors, explaining the effects of the levels.The concentrations of these pollutants in the ambient air are measured via a network of air monitoring stations located around Singapore.
A sub-index value is computed for each pollutant based on the pollutant’s ambient air concentration. The highest sub-index value is then taken as the PSI value. In other words, the PSI is determined by the pollutant with the most significant concentration.
During the haze epi, PM2.5 is the most significant pollutant. And this is why we emphasize so much on filters that can protect you against particle pollutants. Such as N95 facial mask and the Purlife Indoor Air Purifier.