GRAP-4 curbs return in Delhi as air quality turns severe

New Delhi: The Centre's air quality panel for Delhi-NCR on Monday invoked stringent measures under Stage 4 of the air pollution control plan as the region's air quality turned "severe" due to unfavourable meteorological conditions, according to an official order.

The curbs under Stage 4 of the Graded Response Action Plan (GRAP) for winters include a ban on all construction and demolition activities, including public projects such as highways and flyovers, and on the entry of trucks carrying non-essential goods into Delhi.

Delhi's 24-hour average air quality index, which was 379 at 4 pm, breached the 400 mark around 10 pm amid extremely calm winds and "buildup of an inversion layer adversely affecting the vertical mixing height".

Vertical mixing height is the height above the surface throughout which a pollutant can be dispersed.