As Delhi grapples with deteriorating air quality due to unfavourable weather conditions, the Centre’s air quality panel for Delhi-NCR on Monday imposed the strictest Stage 4 curbs under the winter air pollution control plan.

The plan includes a ban on all construction activities, as the region’s air quality deteriorated to ‘severe’ due to unfavourable weather conditions. During the winter season, stage 4 curbs under the Graded Response Action Plan (GRAP) also include a ban on the entry of polluting trucks carrying non-essential goods into Delhi and mandatory shifting of school classes, except those for X and XII, to hybrid mode.

The urgent step to impose Stage 4 curbs was prompted by the major drop in AQI, which breached the 400 mark on Monday night. Delhi’s 24-hour average Air Quality Index (AQI) was 379 at 4 pm.

The air quality in the national capital dropped amid extremely calm wind conditions and the buildup of an inversion layer, which adversely affects the vertical mixing height—the height up to which pollutants can disperse.

The decision to further step up anti-pollution measures came just hours after the Commission for Air Quality Management (CAQM) implemented restrictive measures under GRAP Stage 3, after AQI in Delhi breached the 350 mark in the afternoon.

According to the revised GRAP schedule, classes for students in grades VI-IX and XI in Delhi, Gurugram, Faridabad, Ghaziabad, and Gautam Buddh Nagar must operate in hybrid mode (physical and online) under Stage 4.

Classes up to grade V are required to shift to hybrid mode under Stage 3. Parents and students have the option to choose online education wherever available. Stage 4 also includes a ban on all construction and demolition activities, including public projects like highways, flyovers, power lines, and pipelines. Non-essential diesel trucks are prohibited from entering Delhi.

Public, municipal, and private offices must decide on allowing only 50 percent of staff to work in offices, with the remaining staff working from home. States may consider additional measures like closing colleges and non-essential businesses and implementing odd-even vehicle restrictions.

Under Stage 3, imposed earlier in the day, the use of BS-III petrol and BS-IV diesel cars (4-wheelers) is restricted in Delhi and nearby NCR districts. Persons with disabilities are exempt. Stage 3 also bans non-essential diesel-operated medium goods vehicles with BS-IV or older standards in Delhi.

During winters, Delhi enforces restrictions under GRAP, which categorises air quality into four stages: Stage I (Poor, AQI 201-300), Stage II (Very Poor, AQI 301-400), Stage III (Severe, AQI 401-450), and Stage IV (Severe Plus, AQI above 450).

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