For the third consecutive day, the air quality in the national capital was in the severe category on Tuesday.
According to the Central Pollution Control Board (CPCB) data, the overall air quality index (AQI) in the national capital on New Year's Day was 404, while the Centre-run System of Air Quality and Weather Forecasting (SAFAR) recorded an AQI of 405, both of which are under the 'severe' category.
Nineteen areas in Delhi recorded 'severe' pollution, while 14 witnessed 'very poor' air quality, the CPCB data showed.
Ghaziabad and Noida recorded 'severe' air quality, while in Faridabad and Gurgaon recorded it was in the 'very poor' category.
The overall PM2.5 level (fine particulate matter in the air with a diameter of less than 2.5 micrometer) was recorded at 280 and the PM10 level at 465 in Delhi, the CPCB said.
The SAFAR has said the air quality would improve slightly "provided that no additional local emissions are added on New Year eve".
"Any new trigger in terms of additional local emission, particularly from open fire, pyrotechnic display and fossil fuel burning may make air heavier and thick with low ventilation, and may lead to rapid deterioration in air quality to severe-plus range," the SAFAR said.
But despite warnings, several instances of firecracker bursting, before and after the time limit fixed by the apex court, were observed in Delhi-NCR during New Year celebrations.
The SAFAR said the air quality in Delhi is likely to remain in the 'severe' zone for the next two days as weather conditions are more adverse now.
"The deterioration in speed of moisture-laden wind from west may become fatal at this stage and any new trigger, in terms of local emission, particularly from open fires, firecrackers and (burning of) fossil fuels will fast deteriorate the air quality and keep it in the 'severe' category," it said.
The India Meteorological Department (IMD) and SAFAR said the air quality is likely to remain in the 'severe' category owing to low wind speed, which is highly unfavourable for dispersion of pollutants.
The authorities warned that moderate fog and emissions during night hours may result in deterioration of the air quality and this situation may prevail till Wednesday.
The SAFAR also pointed out that a consistent day-night trend is being observed for the past one week.
"During night, a combination of calm wind and colder condition is elevating the pollution level. In many locations, 24-hour rolling average (AQI) is touching 'severe' levels for a few hours, whereas during the day wind is picking up speed slightly and temperature is increasing to keep the level in the 'very poor' range," it said.