<span style="color: #222222;">National Capital Delhi's air quality has deteriorated to the severe category today as a thick smog engulfed the national capital and prevented dispersion of pollutants. </span><br />'' <br />'' <span style="color: #222222;">According to Central Pollution Control Board, CPCB, the overall Air Quality Index was recorded 433 at 8 PM today. </span><br />'' <span style="color: #222222;"> </span><br />'' <span style="color: #222222;">This is the fourth time this season that the air quality in the city has worsened to the 'severe' category. </span><br />'' <br />'' <span style="color: #222222;">The first time the air quality dipped to this category this year was just two days before Diwali. </span><br />'' <br />'' <span style="color: #222222;">A day after Diwali, on 7th of last month and on 12th of this month, the air quality again slipped to the severe category.</span><br />'' <span style="color: #222222;"> </span><br />'' <span style="color: #222222;">Officials said they are closely monitoring the situation and if the conditions prevail for 48 hours emergency measures will be taken.</span><br />''