<span style="color: #222222;">Delhi's air quality turned severe today with slow wind speed allowing the accumulation of locally generated pollutants. Thick smog engulfed the national capital in the morning. The air quality is expected to improve by tomorrow as the wind speed is likely to pick up.<br />''<br />''The air quality index, AQI of the city was 401 at 10 AM, which falls in the severe category.  An AQI between 0 and 50 is considered good, 51 and 100 satisfactory, 101 and 200 moderate, 201 to 300 poor , 301 to 400 very poor and 401 to 500 severe.</span>