A thick layer of smog covered Delhi on Tuesday as the national capital witnessed 'very poor' air quality with AQI at 341. Areas like Bawana, Jahangirpuri and Wazirpur recorded 'severe' air with AQI at 419, 414 and 410 respectively. However, Lodhi Road and Mandir Marg saw 'moderate' air with AQI at 199 and 197 respectively.