New Delhi, Nov. 7 -- Delhi's official air quality index (AQI) hit 382 on Friday, the city's worst since January 19, and may still be understating pollution levels after 13 new stations were added to the monitoring network in October, an HT analysis of Central Pollution Control Board (CPCB) data has found. Without the new stations, Friday's 4pm bulletin would have read 393. Most of the new monitors, set up by the Delhi Pollution Control Committee (DPCC), the city government's pollution regulator, are on the city's periphery, but older stations just as far out, in areas just as built-up, show much higher readings. HT's analysis found the levels of PM2.5 --- the biggest contributor to pollution during the winter smog spell --- at the new stations are about 35% lower than those at their neighbouring stations. Their effect on the AQI readings showed on Friday amid Dhanteras, which is typically accompanied by heavy traffic on the city's roads. CPCB's official figure is a plain average of every station's AQI, each a rolling 24-hour average (the figure at 4pm becomes the day's bulletin). From 7am to noon it stayed between 389 and 391, in the "very poor" band. Without the 13 new stations, which averaged about 350 at 10am, it would have been 401 to 403, in the "severe" band, the worst on the scale. The share of stations that were in the "severe" band underlines this divergence. At 7am, 28 of Delhi's 59 stations, or 47%, reached this band. It peaked at 11am and at noon, with 53%, or 31 in the severe band. Without the 13 new stations, 59% of the remaining 46 stations were severe at 7am and peaked at 65% at noon. The median station, the middle one when all are ranked, read 410, itself severe, against 396 with all 59 counted at 7am. It matters because Delhi's pollution crisis has not eased as the city heads into Diwali. So-called green firecrackers are allowed this year and illegal sales of banned crackers have continued, in a stretch of the year when the air is usually at its worst, with farm fires at their peak, winds weakening and cooler nights trapping smoke near the ground. Friday's spike began late on Thursday as winds from the farm-fire belt of Punjab and Haryana blew in a few hundred metres above ground. Over the city itself, the wind near the ground fell almost still and a layer of warm air held Delhi's own emissions close to the ground. The festive rush added to those local emissions. From Friday morning, shoppers heading to markets for Dhanteras and Diwali, and families driving across the city to deliver sweets and gifts, choked arterial roads....