Delhi’s air turned shockingly bad on Tuesday, crossing the severe pollution mark with an Air Quality Index (AQI) of 428, the Central Pollution Control Board (CPCB) reported. This alarming jump from Monday’s AQI of 362 forced the central government to activate Stage III of the Graded Response Action Plan (GRAP) right across Delhi-NCR. Why did air quality take such a nosedive? The Commission for Air Quality Management (CAQM) pointed fingers at calm winds, a stable atmosphere, and other unfavourable weather conditions. These factors trapped harmful pollutants just near the ground, leaving everyone to gasp for clean air. The “severe” AQI range of 401-450 means even healthy people can feel the harmful effects, while those with breathing or heart problems face serious risks. So, what changes under Stage III of GRAP? Non-essential construction, stone crushing, and mining must stop immediately. Schools up to Class 5 are told to switch to online or hybrid classes, giving parents the choice to keep kids learning safely from home. Also, Delhi and nearby areas are banning BS-III petrol and BS-IV diesel cars, except vehicles for people with disabilities. These new curbs add to existing efforts aimed at cutting vehicle emissions, road dust, and choking waste burning. But why does Delhi’s air get this bad every winter? Calm winds, cold temps, and a shallow mixing layer block pollutants from dispersing. Vehicles, industries, stubble burning in neighbour states, and festive firecrackers all pour more dirty smoke into the air. This toxic cocktail traps itself in the city, ruining visibility and health. GRAP started in 2017, with four stages based on how bad the pollution is: Stage I (Poor, AQI 201–300), Stage II (Very Poor, 301–400), Stage III (Severe, 401–450), and Stage IV (Severe Plus, above 450). Officials warn that if pollution worsens, Stage IV steps like halting trucks, closing all schools and colleges, and halting all construction could kick in. As the smog thickens and the hazy skyline returns early this winter, Delhiites brace themselves for another year-long battle against the city’s notorious toxic air. "The situation is critical and demands urgent action," warned environmental experts watching the sky turn dark. Are you ready to fight the smog?