Delhi's air hits a 100-day high at AQI 244 and GRAP Stage I comes into force across the NCR: what is barred

The plan has four stages that depend on the index and are tightened as the air gets worse. The commission can act on forecasts and not only on readings, which is why Stage I was invoked when the forecast said the air would stay poor.

Stage I concentrates on dust, waste and vehicles. Agencies are to sweep roads mechanically and sprinkle water, control dust at construction sites, manage waste, check polluting vehicles more strictly, improve traffic management and control emissions from industries, power plants and brick kilns. It does not ban private cars, close schools or stop construction. A revised schedule approved in September moved two measures from Stage II to Stage I: some measures on diesel generator sets, and limits on the entry of buses that meet only BS-IV or older standards. Construction sites must cover materials and keep dust inside their boundaries, and open burning of waste is not allowed. Residents are asked not to burn leaves or rubbish, to share rides and use public transport where they can, and to report violations.

The commission told departments to act quickly on dust and ordered strict action against officials, project owners and agencies that break the rules.

Environment Minister Manjinder Singh Sirsa said Stage I came later in the season than in many years. The Delhi government's 11-point plan involves nearly 30 agencies. Vehicles without a valid pollution-under-control certificate will not be given fuel, parking charges will be doubled across Delhi except at Metro parking, and action against end-of-life vehicles will be stepped up. Staggered hours and work from home are planned for the municipal corporation and government offices. From 1 November to 31 January, vehicles registered outside Delhi that do not meet BS-VI standards will be barred from entering the city, and CNG and electric vehicles are exempt.

Where the pollution comes from

Dussehra effigies were burnt a day before the deterioration, though no direct link has been established. According to the IITM Pune decision support system, transport contributed about 20.5 per cent of Delhi's PM2.5 on Wednesday, with the estimate falling to 17.3 per cent on Thursday. Stubble burning contributed up to 8 per cent, homes 5.2 per cent, industries in the surrounding region 4.3 per cent, construction 2.8 per cent, waste burning 1.8 per cent and road dust 1.4 per cent. Among nearby districts, Sonipat's share was forecast to fall and Ghaziabad's to rise.

Whether the air improves depends on the wind. A ventilation index below 6,000 square metres per second, with wind below 10 km an hour, is unfavourable for dispersing pollutants. The early-warning system expects the poor category to continue from 23 to 25 October, and the India Meteorological Department and IITM Pune also forecast poor air in the coming days. With winter approaching, residents are advised to check the daily index before planning outdoor activity.