New Delhi, Nov 6 : After three consecutive days of Air quality remaining into Severe category, the quality Index improved slightly in the national capital city on Sunday morning following which the GRAP Stage IV measures may be reviewed. According to the System of Air Quality and Weather Forecasting And Research (SAFAR), the overall AQI of the city improved further on 331, however in the very poor category. The concentration of both PM 2.5 and PM 10 was recorded at 331 under the very poor category and 211 under the poor category respectively this morning. Delhi's AQI returned to the 'very poor' category after a change in wind direction due to southeasterly, while local winds speeds also picked up. "The AQI will start improving faster now as surface wind will pick up to enhance dispersion and the direction of stubble transport wind also is changing. The AQI will be very low to mid part of very poor by the 6th of November," said Prof. Gufran Beig, Founder Project Director, SAFAR. However, Prof Beig also added that the relief is short lived. "The AQI will start deteriorating from the 8th evening as the stubble wind will again turn from the burning side," he said. Meanwhile, the Commission for Air Quality Management (CAQM) in NCR, is likely to hold a review meeting on Sunday in the light of improving air condition. The CAQM had imposed Stage IV measures of the Graded Response Action Plan (Grap) on Thursday evening that bans the entry of diesel vehicles that were not BS VI in Delhi. The Delhi government on Friday banned the entry of trucks other than essential services in the national capital following the introduction of GRAP IV. The government has also constituted a six-member committee to monitor truck entry in the national capital city. "Only CNG, petrol and electric vehicles will be allowed to enter Delhi. There will also be a ban on medium and heavy vehicles of diesel registered in Delhi, which are not connected to the essential services. Small vehicles with diesel engines which are not BS6 compliant will also be banned," Delhi Environment Minister Gopal Rai said on Friday. /IANS