New Delhi, Dec. 21 -- As Delhi's air quality crisis deepens, the national capital woke up on Sunday with a 'severe' air quality index of 438, accompanied by reduced visibility due to thick smog. The residents have taken to social media to report eye irritation, throat discomfort, and breathing difficulties.

Notably, the Commission for Air Quality Management (CAQM) categorises AQI based on the following ranges: 0-50 is 'good', 51-100 is 'satisfactory', 101-200 is 'moderate', 201-300 is 'poor', 301-400 is 'very poor', and 401-500 is 'severe'.

In response to deteriorating air quality, the authorities have invoked all measures under the Graded Response Action Plan (GRAP) Stage IV across the Delhi-NCR region.

The restrictions under GRAP-IV ...