Many are not aware that there is a difference in PSI reading and ug/m3 (microgram per meter cube). This is because the health warning levels are different.
NEA 24 hour average and 3 hour average readings are in PSI. NEA 1 hour average reading is in ug/m3 (not PSI).
S'pore official health advisory is based on 24 hours average PSI reading. However, for our personal health concern, we should base our activities on 1 hour real time reading in PSI, a reference we are familiar with. NEA does not provide real time 1 hour data in PSI.
*Health advisory by NEA in PSI for 24 hour averaged reading:
0 -50 Good
201-300 Very Unhealthy
more than 300 Hazardous
*Health advisory by NEA in ug/m3 for 24 hour averaged reading:
less/equal 55 Normal
more than 250 Very High
It seems that NEA has changed their reference parameter this year for haze reporting in ug/m3. It has chosen to use such neutral descriptive words, which render them useless for public health reference.
**Formal descriptive reference from NEA and MOH website last year:
Index Category PSI 24hrPM2.5 ug/m3
Good 0-50 0-12
Moderate 51-100 13-55
Unhealthy 101-200 56-150
Very Unhealthy 201-300 151-250
Hazardous above 301 above 251
Thus, on 26/8/16 at 12 noon Spore West area hitting 216 ug/m3 (not PSI) is very alarming, as it is in the very unhealthy range !
1) US EPA adopts 35 ug/m3 as unhealthy limit for 24 hrs PM2.5 which is a more stringent standard than S'pore.
2) For real time data on PSI please refer to : aqicn.org - which provides real time air pollution information for more than 60 countries in the world