Delhi’s AQI after Diwali was reported as 483, 370, 776 and above 1,000 by different sources.
The official scale tops out at 500, and readings above that are shown as 500 plus.
Private platforms can use different methods and monitors.
Time of day and station choice also change the figure.
The CPCB reading of 483 is in the severe category.
Station readings reported by Organiser include Vivek Vihar at 445, Burari Crossing at 441, Jahangirpuri between 433 and 442, Rohini between 430 and 438 and DTU between 430 and 434.
Other readings in that report include North Campus at 433, Bawana at 427, Ghazipur at 418, Mundka at 417, Punjabi Bagh at 408 to 409 and Narela at 407.
Daily Jagran lists New Tehsil-Loni in Ghaziabad at 463 and Sonia Vihar in Delhi at 457, and gives Burari Crossing as 441 in one list and 449 in another, so station figures differ within and between reports.
Not every station was in the severe range: Organiser lists CRRI Mathura Road at 396, Dr Karni Singh Shooting Range at 361 and Najafgarh at 340.
The Hans India and Daily Jagran city tables, citing CPCB data for November 9, give Delhi a figure of 370, in the very poor category, which differs from the 483 overall figure.
The Hans India also reports a reading of 776 for Delhi from AQI.in at 6:51 am on Monday, which comes from a private platform and not from the CPCB.
Organiser reports that Swiss-based IQAir recorded readings above 1,000 in Shahdara and Defence Colony, without giving times or exact values, and says the difference reflects variations in methodologies.
The Air Quality Index runs from 0 to 500, with 0 to 50 good, 51 to 100 satisfactory, 101 to 200 moderate, 201 to 300 poor, 301 to 400 very poor and 401 to 500 severe, according to Organiser.
Smog over the Indus-Ganga Plain, NOAA satellite image of 2017 (file image), Wikimedia Commons, public domain
