Air Quality in Delhi-NCR Plummets, AQI Hits 400; Strict Graph-4 Restrictions Now in Place

New Delhi (The Uttam Hindu): Due to deteriorating air quality in Delhi on Monday night, GRAP-4 restrictions have been re-imposed across Delhi-NCR. Delhi's average air quality index (AQI) reached 399 at 9 pm on Monday and crossed 400 at 10 pm. The air quality reached the 'severe +' category, due to which it was decided to re-implement the fourth phase of the Graded Response Action Plan (GRAP) in an emergency meeting. CAQM issued a statement saying that following the instructions of the Supreme Court, the sub-committee implements the fourth phase of the schedule under GRAP with immediate effect, which was extensively revised and released on December 13.

CAQM has cited the Supreme Court order in which the court had said that if the commission finds the AQI crossing the 350 mark, then the third phase measures should be implemented and if the AQI crosses 400, then the fourth phase measures should be implemented again. Earlier, Group 3 restrictions were imposed in the entire NCR as the AQI had crossed the 350 mark.

Air quality parameters further deteriorated due to a sharp decrease in the mixing layer height and zero-wind conditions in Delhi. As a result, the Sub-Committee on GRAP was closely monitoring the air quality situation in Delhi. The Sub-Committee noted that the Air Quality Index level was almost touching the 400 mark, i.e., 399 at 9 am and 401 at 10 am, crossing the 400 mark. Let us tell you that there are a total of four stages in GRAP. The first stage is implemented when the AQI is between 201 to 300. After this, the second stage is implemented when the AQI is between 301 to 400, while the third stage is implemented when the AQI is between 401 to 450. At the same time, the fourth stage is implemented when the AQI is more than 450.