The overall air quality in the city was 370 at 9.45 am; it was 'severe' with an AQI of 404 at 4 pm Friday. An AQI between 0-50 is considered 'good', 51-100 'satisfactory', 101-200 'moderate', 201-300 'poor', 301-400 'very poor' and 401-500 'severe'. 

An AQI above 500 falls in the 'severe plus' category. -- PTI