It was a hazy night yesterday and naturally everyone went into crazy mode. As people went about their evening tasks, walking, eating, talking or complaining, one of the top websites on everyone’s mind was… NEA’s.

People started posting various screenshots from NEA’s 1 hour PM2.5 readings or AQICN, complaining about the sudden surge in haze. Some were naturally annoyed that NEA does not release a 1 hour consolidated PSI figure because the 3 hour PSI obviously did not seem to tally with what they were seeing out there.

But the situation last night actually seemed to show why a 1 hour consolidated PSI figure doesn’t work. Simply put, a centralised figure wouldn’t be able to tell you what to expect when you walk outdoors.


Judging by the PM2.5 readings across Singapore at 11pm last night, it would be near impossible to give an hourly figure to represent the entire Singapore. The West were languishing in haze, with a pretty hazardous 471 reading, while the North side were probably wondering what the fuss was about.

Even if one were to look at the “back calculated” 1 hour PSI reading from sites like ‘Realistic’ Hourly PSI, you would probably see a PSI of around 200+. To someone living in the West, obviously the 1 hour PSI would look like a bunch of lies because “it obviously does not look 200+” and those living in the North would obviously feel its rubbish cause it didn’t appear to be hazy. Don’t get me wrong though, the hourly PSI readings are fine but perhaps more when the haze is spread across Singapore, rather than localised.

The good thing coming out of this was people turned to NEA’s 1 hour PM2.5 readings for a better gauge of instantaneous conditions. After all, most other sites use NEA’s data to form their own figures so those that are prepared to believe figures from other sites should also believe NEA’s data, right?

But one thing I’d like to suggest… perhaps NEA could include a table on what level of PM2.5 corresponds to what level of health warning on the page itself.