CAQM revokes Stage 4 of Grap as air improves to ‘very poor’ in the Capital

The 24-hour average Air Quality Index (AQI) was recorded at 369 (”very poor”) at 4pm on Tuesday, a significant improvement from Monday’s 406 (”severe”).

The Commission for Air Quality Management (CAQM) revoked Stage 4 of the Graded Response Action Plan (GRAP) for the National Capital Region (NCR) on Thursday after Delhi’s air improved to the “very poor” category on Tuesday, aided by stronger winds and the withdrawal of a western disturbance.

The AQI had been gradually declining through the day. (Sunil Ghosh/HT Photo)

The 24-hour average Air Quality Index (AQI) was recorded at 369 (”very poor”) at 4pm on Tuesday, a significant improvement from Monday’s 406 (”severe”). The AQI had been gradually declining through the day, starting at 400 at 9am, dipping to 396 by 11am, and 358 by 7pm, data showed.

The AQI was 406 (“severe”) on Monday, 409 (“severe”) on Sunday and 370 (“very poor”) on Saturday.

Mahesh Palawat, vice-president at Skymet, explained the trend, saying, “Western disturbances (WD) reduce wind speeds, causing pollutants to stagnate. On Tuesday, wind speeds were 10-12 km/h during the day but slowed to 2-3 km/h by evening. Winds are expected to pick up again over the next two days before another WD influences the region.”

Delhi’s winter months typically see worsening air quality, prompting the phased implementation of Grap, which has four stages based on AQI levels. Stage 1 applies to “poor” air (AQI 201-300), Stage 2 to “very poor” air (AQI 301-400), Stage 3 to “severe” air (AQI 401-450), and Stage IV to “severe plus” (AQI above 450).

Stages 1 and 2 were implemented on October 14 and October 21, respectively. On December 16, Grap’s Stage 3 was triggered when the AQI crossed 350. Later that night, the AQI exceeded 400, prompting the activation of Stage 4 measures, which include halts to all construction and demolition work, curbs on non-essential commercial activities, potential work-from-home directives for central government employees, and possible school closures for middle and high school students.

In its latest notification, CAQM highlighted the general improvement in air quality since December 23, allowing the rollback of Stage 4 measures. However, restrictions under GRAP Stages I, II, and III remain in place as a precautionary measure. Officials noted that the Commission would continue to monitor air quality closely and review the situation periodically.

The Air Quality Early Warning System (AQEWS) has predicted that Delhi’s air quality will remain in the “very poor” category through Wednesday and Thursday. It expects air quality to fluctuate between “moderate” and “very poor” over the following six days.