The Commission for Air Quality Management (CAQM) on Monday imposed stage two measures in Delhi-NCR under the Graded Response Action Plan (GRAP) as air quality slipped into the ‘very poor’ category.”The Air Quality Index (AQI) of Delhi, which was observed 117 (‘Moderate’ Category) on October 31, has exhibited a sharp rise with AQI of 261 (‘Poor’ Category) on November 1 and has further increased to 324 (‘Very Poor’ Category) on November 2 owing to unfavourable meteorological conditions.,” the CAQM said in a statement.It added that the India Meteorological Department (IMD) and the Indian Institute of Tropical Meteorology forecast that Delhi’s overall air quality is likely to remain in the ‘Very Poor’ category in the coming days.GRAP is a set of emergency measures that kick in to prevent further deterioration of air quality once it reaches a certain threshold.The first stage, GRAP-1, kicks in when the AQI is between 201 and 300; the second stage, GRAP-2, is invoked when the AQI is between 301 and 400; GRAP-3 kicks in between 401 and 500; and GRAP-4 is invoked when the AQI is more than 450.In September, the CAQM modified the GRAP framework, bringing changes like the extension of restrictions on the plying of BS-III petrol and BS-IV diesel or below-standard LMVs (four-wheelers) to Sonepat in Haryana under GRAP-3.Earlier, these restrictions were limited only to Gurugram, Faridabad, Ghaziabad and Gautam Budh Nagar.