Delhi's Air Quality Index (AQI) stood at 484, the worst this season, at 8 am, according to the Central Pollution Control Board (CPCB).
Delhi's air quality worsened to the 'severe plus' category on Monday with the city recording an AQI of 484. Tighter pollution control measures, including a ban on truck entry and suspension of construction at public projects, came into force in the morning.
The dense toxic smog caused visibility to drop sharply in the morning.
According to officials, visibility at Safdarjung airport was 150 metres.
Delhi's Air Quality Index (AQI) stood at 484, the worst this season, at 8 am, according to the Central Pollution Control Board (CPCB).
The AQI was 441 at 4 pm on Sunday and rose to 457 by 7 pm due to unfavourable weather conditions.
With the AQI crossing 450, the Commission for Air Quality Management in the National Capital Region and Adjoining Areas ordered the implementation of Graded Response Action Plan (GRAP) Stage-IV restrictions in Delhi-NCR.
According to the order, no trucks will be allowed into Delhi except for those carrying essential items or using clean fuel (LNG/CNG/BS-VI diesel/electric).
Non-essential light commercial vehicles registered outside Delhi will also be prohibited, except for EVs and CNG and BS-VI diesel ones.
Delhi-registered BS-IV or older diesel medium and heavy goods vehicles are banned, except for those in essential services, the order said.
All construction activities, including highways, roads, flyovers, power lines, pipelines and other public projects, have been suspended.
The CAQM recommended that offices in the National Capital Region (NCR) work at 50 per cent capacity, with the rest working from home.
The Delhi government asked all schools to discontinue physical classes for all students, except those in classes 10 and 12, from Monday.
An AQI of 400 or higher is deemed 'severe' and it can have an adverse effect on both healthy individuals and people who already have medical conditions.
First implemented in 2017, the GRAP is a set of anti-air pollution measures followed in the capital and its vicinity according to the severity of the situation.
It classifies the air quality in the Delhi-NCR under four different stages: Stage 1 - 'poor' (AQI 201-300), Stage 2 - 'very poor' (AQI 301-400), Stage 3 - 'severe' (AQI 401-450) and Stage 4 - 'severe plus' (AQI above 450).
Delhi recorded a minimum temperature of 16.2 degrees Celsius, 3.9 degrees above normal. The maximum temperature is expected to settle at 27 degrees Celsius, according to the India Meteorological Department (IMD).
The weather department has predicted very dense fog during the day.