SAFAR's forecast said the quality of air over Delhi was in 'severe' category. (Reuters photo)

Delhi's battle with toxic, "severe" air may intensify in the new year as authorities have warned that quality of air will reach emergency level on Tuesday if additional local emission, particularly from bursting fire crackers and burning of fossil fuel, continues.

The Centre-run System of Air Quality and Weather Forecasting (SAFAR) said any trigger will make the air heavier, thicker and may lead to rapid deterioration in quality to severe-plus range.

"Any new trigger in terms of additional local emission, particularly from open fire, pyrotechnic display and fossil fuel burning, may make the air heavier, thicker, and with low ventilation it may lead to rapid deterioration in the quality of air to severe-plus range," the SAFAR said in its new year's forecast.

It further said the quality of air over Delhi was in 'severe' category and forecast it to remain in the severe zone for the next two days.

"Dense to moderate fog is likely to prevail, adversely affecting air quality. Increase in wind speed and change in direction (less moisture laden) can provide some respite, the probability of which is less," the SAFAR said.

The last ten days of the year witnessed spells of severe pollution, episodes when air quality slipped to severe level by night and remained in the category and then slightly improved to very poor.

Authorities have said that during the nights, combination of calm wind and colder conditions was elevating the pollution level. At many locations, the 24 hour rolling average (AQI) was touching severe levels for few hours. During the day wind speed was picking up slightly and temperature was increasing to keep the level at the very poor range.