Delhi's air quality remained in the severe category for the third day on Monday as wind speed and other meteorological factors remained unfavourable for dispersion of pollutants. <br />''<br />''<br />''Hazardous pollution would continue to plague the national capital till Christmas evening.<br />''<br />''<br />'' Delhi is facing its highest pollution level since Diwali. People have been advised by the authorities to minimise outdoor activities and avoid the use of private vehicles.<br />''<br />''<br />'' The Central Pollution Control Board data showed the overall air quality index, AQI at 448. <br />''<br />''<br />''An AQI between 100 to 200 comes under the 'moderate' category, 201 and 300 is considered 'poor', 301 and 400 'very poor', while that between 401 and 500 is 'severe'.<br />''<br />''<br />''<span style="color: #222222;">The overall PM 2.5 level was recorded at 407 and the PM 10 level at 581.</span><br />