Realistics PSI Readings

Sick of the 3-hr average PSI?
We calculate the actual hourly PSI!


Actual PSI*

Reported PSI



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Actual PSI*


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* NEA's PSI reading is based on a 3-hour average. While it is a good measure of exposure, it tends to dampen the impact of sharp drops or increase in PSI readings in an hour.

We have created what we think is a right implementation of NEA's official PSI formula on to deduce the actual, hourly PSI measurements from hourly PM2.5 readings. Technical details can be found here.

Update (12am 28th Sept 2015): We have revised our calculations to what we think is the right implementation of NEA's formula to derive hourly PSI from hourly pm2.5 readings. This is now no longer an estimate!

Update (11.39am 24th Sept 2015): Thanks Mothership and Asia361 for the feature!
Update (11.14am 8th Oct 2014): Thank you HQ for pointing out a previous mistake in my formula. Calculation has been updated.