The average air quality index (AQI) in Delhi early Tuesday was recorded to be 492 (as of 7 am). The AQI in Alipur, Anand Vihar, Bawana, Narela, Pusa and Sonia Vihar, meanwhile, touched 500, which is the maximum index (as per the Central Pollution Control Board).

The AQI in Delhi-NCR is in the ‘severe plus’ category. AQI between 0-50 is considered “good”, 51-100 is “satisfactory”, 101-200 is “moderate”, 201-300 is “poor”, 301-400 is “very poor”, 401-500 is “severe” and above 500 is a “severe plus”.

Residents in India's northern states woke up to another day of poor air quality on Tuesday, as a layer of dense fog shrouded most of the region, and pollution in the capital Delhi remained severe.