New Delhi, Nov 28 : As the winter approaches, a layer of smog continued to envelope the national capital on Monday with the overall AQI registered at 313 under the "very poor" category. According to the System of Air Quality and Weather Forecasting And Research (SAFAR), the concentration of both PM 2.5 and PM 10 in the environment was recorded at 313 and 202 (moderate), respectively. As per the SAFAR forecast, the city's air quality will further deteriorate on Tuesday with AQI escalating to 324 . An AQI between zero and 50 is considered "good"; 51 and 100 "satisfactory"; 101 and 200 "moderate"; 201 and 300 "poor"; 301 and 400 "very poor"; and 401 and 500 "severe". The AQI at Anand Vihar, Patparganj and ITO were recorded at 379, 362 and 319, respectively, all under the "very poor" category on Monday morning, according to the Central Pollution Control Board. The prolonged exposure to poor air quality may lead to respiratory illnesses. While Noida registered an AQI of 372 ("very poor"), Gurugram's figure slightly improved to 276 ("poor"). /IANS