The air quality index of the Central Pollution Control Board (CPCB) had a score of 487 on a scale of 500, indicating 'severe' levels of pollution, which can affect even healthy people and "seriously impact" those with existing diseases.
If the score touches 500 and persists there for at least 48 hours, measures like odd-even and a ban on construction and demolition activities will come into force across the Delhi NCR under the Graded Response Action Plan (GRAP).
But confusion prevailed over the measures announced by the Supreme Court-mandated Environment Pollution (Prevention and Control) Authority (EPCA) including lowering metro fares during off-peak hours and hiking parking rates by up to four times.
The Delhi Metro Rail Corporation Limited (DMRC) said they were on course to augment their services in terms of increasing frequency but remained non-committal on slashing fares temporarily.
The civic bodies are yet to announce any hike in parking fees.
However, the EPCA had made it clear yesterday that its orders are legally binding and have to be enforced once the chief secretaries of the respective states issue them.
It was the Environment Ministry which, in January, had empowered the EPCA through a gazette notification to enforce the GRAP to combat air pollution in the Delhi-NCR region.
Meanwhile, the Delhi government announced that all schools in the national capital will remain closed till Sunday in view of the "unbearable" air pollution.
According to the forecast of the Union Ministry of Earth Sciences' System of Air Quality and Weather Forecasting And Research (SAFAR), the 24-hour-average concentrations of PM2.5 and PM10 will be around 420 and 678 micrograms per cubic metre.
The corresponding safe standards of these ultra-fine particulates, up to 30 times finer than the width of a human hair, are 60 and 100 respectively.
Secretary, Ministry of Earth Sciences, Madhavan Rajeevan said the smog in Delhi is not localised, but spread across the entire region. He said the conditions will persist for another two-three days.
The SAFAR suggested that the "sudden" intrusion of pollutant-laden smoke from neighbouring Punjab and Haryana from the night of November 6 led to the spike as the high quantity of moisture in the city's air trapped the particulates.
"There is absolutely no wind movement. Moreover, temperature is also not coming down substantially which could have resulted in the conversion of the fog into water and subsequent dispersion of the suspended particulates," CPCB scientist Dipankar Saha explained.
Apart from Delhi, neighbouring Faridabad, Ghaziabad, Gurgaon and Noida were also in the 'severe' category.
Residents of the city complained of heavy breathing and watery eyes as the smog did not even spare living rooms or underground metro stations.
Yesterday, with a score of 448 in a scale of 500, the air quality index was at the year's worst.
The Indian Medical Association had declared a "public health emergency" and appealed to the government to stop outdoor sports and other such activities in schools to protect the health of children.
The Delhi government had also issued a health advisory for high-risk people, including children, the elderly, pregnant women and those suffering from asthma and heart ailments.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)