The air quality of the national capital remains 'very poor' for the third consecutive day on Friday and was likely to further deteriorate to the 'severe' category in some parts of the city on Saturday.

According to the Centre-run System of Air Quality and Weather Forecasting (SAFAR), the overall air quality index (AQI) of Delhi was recorded at 388 on Friday, against Thursday's 334.

The SAFAR model forecast suggests calm surface winds and a decrease in ventilation coefficient for the coming days and the condition was conducive for the pollutant accumulation.

"AQI is forecasted to stay at the border of very poor to the severe category until Saturday," SAFAR said.

It said the overall Delhi AQI was in the lower end of the very poor category on Wednesday.

The city had witnessed drastic improvement in the air quality last week as the AQI was recorded in double digits at the 'satisfactory' category, after being seeing few of the worst air quality days in November.

The air in the national capital was so toxic after Diwali that the Environmental Pollution (Prevention and Control) Authority (EPCA) had declared a public health emergency in Delhi-NCR and had advised people, especially children and the aged, to limit their exposure to the environment.