A thick blanket of smog enveloped North India including the national capital. Delhi today woke up to 'severe' air quality due to blanket of thick haze, as pollution levels breached the permissible standards by multiple times. <br/><br/>The rapid fall in air quality and visibility began last evening as moisture combined with pollutants shrouded the city in a thick cover of haze.<br/><br/>The Central Pollution Control Board, CPCB, by 10 am, recorded 'severe' air quality, meaning the intensity of pollution was extreme. <br/><br/>Board's air lab chief Dipankar Saha said, high moisture level in the air has trapped emission from local sources and hanging low over the city in the absence of wind.<br/><br/>A 'severe' Air Quality Index comes with the warning that air affects healthy people and seriously impacts those with existing respiratory or cardiovascular diseases. <br/><br/>The CPCB also recorded 'severe' air quality in the neighbouring Noida and Ghaziabad.