Investigations

Investigations

Special investigations

Standalone investigations that go beyond the daily record.

When the monitors stopped giving PM2.5 and PM10 values

20 to 21 October 2025 and 8 to 9 November 2026 | Published 9 November 2026 | Public record

At 1 AM on 9 November 2026, 36 of the 59 stations in CPCB's hourly data for Delhi had no PM2.5 reading, and 23 had one. Counted on each night's own list of stations, that was the fewest with a reading in any hour from 8 PM to 7 AM across the 36 nights from 4 October 2026 to Diwali.

Read the hour-by-hour record, the Supreme Court's orders and the source files (English)

13 new monitors lowered Delhi's AQI on all 26 days, by 11.6 points on average

13 October to 7 November 2026

Thirteen monitors added in October lowered Delhi's 4 PM AQI by 11.6 points on average from 13 October to 7 November 2026.

Read the investigation (English)

The destruction of Delhi's air

1980 to July 2026: 46 full calendar years, followed by a partial year

This study separates recent measurements from the earlier historical estimate.

Read the evidence report

CAQM's claims, checked

30 September 2026

The release is checked against the official record.

Read the claims

Delhi's Good or Satisfactory days drop to 63 from 79; AQI 500 station-days climb to 68 from 37

3 November 2026

Delhi's air on CPCB's own record, 1 January to 3 November 2026 against the same window of 2025.

Read the report (English)

Diwali night, 2025: Delhi monitoring coverage

20 to 21 October 2025 | Published 18 October 2026

At 02:00 the saved PM2.5 archive contained readings from 12 stations, compared with 40 at the matched hour one week earlier. The report sets out what the missing observations can and cannot establish.

Read the report and hourly counts (English)

Delhi at AQI 500

2021 to 17 October 2026 | Published 18 October 2026

The report records 1,348 station-days displayed as 500 from 2021 to 17 October 2026. It separates the index cap from measured concentrations and makes gaps in eligible AQI data visible.

Read the report and station-day data (English)

Delhi winter pollution: dates, duties and accountability

Notification 23 June 2026 | Published 18 October 2026

A source-checked guide to the 23 June 2026 notification: different dates, exemptions, public responsibilities and the records needed to assess implementation.

Read the notification guide and official source (English)

Delhi on Dussehra evening, 2026: hour by hour

Evening of 20 October 2026 | Published 20 October 2026

Delhi's hourly index on CPCB's AQI scale from 6 to 10 PM on 20 October 2026, set against the same hours on the five evenings before, city-wide and station by station.

Read the Dussehra evening record (English)

The formula and the figure: CPCB's AQI formula against the AQI CPCB publishes

Delhi, 1 May 2015 to 20 October 2026, and every city in CPCB's bulletin | Published 21 October 2026

On the hour-by-hour calculation that CPCB's published figures track, Delhi's AQI was Very Poor or Severe on 928 days between May 2015 and October 2026. On 926 of them, the method set out in CPCB's own documents gave a higher figure.

Read the investigation (English)

Milan Garden garbage fire: hourly pollution and missing readings

25 to 26 October 2026 | Published 27 October 2026 | Public Report and Executive Summary

The investigation compares 25 surrounding and further station candidates with the same hours on five previous nights. It records local particle peaks and missing readings, without assigning an unverified fire contribution.

Read the Public Report and Executive Summary (English)