New Delhi: Delhi's average air quality index (AQI) breached 400-mark on Wednesday, according to the Central Pollution Control Board (CPCB).
The air quality index from 0 to 100 is considered 'good', 100 to 200 'moderate', 200 to 300 'poor', 300 to 400 'very poor' and from 400 to 500 or above 'severe'.

With the very poor air quality, the Centre on Wednesday decided to watch the situation for a day or more before invoking stricter curbs under Stage 3 of the Centre's air pollution control plan called the Graded Response Action Plan (GRAP) in Delhi-NCR, as forecasts suggested that the situation may improve.

"The sub-committee of the Commission for Air Quality Management (CAQM) for the operationalization of GRAP met today and took stock of the current air quality scenario and forecast of meteorological conditions, as well as the projected air quality index by the India Meteorological Department (IMD) and Indian Institute of Tropical Meteorology (IITM)," an official statement said.

The sub-committee, while comprehensively reviewing the air quality scenario and relevant aspects, noted that as per the air quality forecasts by IMD and IITM, Delhi's average AQI is likely to improve.

Therefore, it was decided by the subcommittee unanimously to watch the situation for a day or more before considering invoking Stage III of GRAP. The ongoing preventive and restrictive actions implemented under Stages I and II of GRAP shall continue for the present and the Sub-Committee shall keep a close watch on the situation for further decision.

Stage 3 curbs include a ban on non-essential construction work and the plying of BS III petrol and BS IV diesel four-wheelers in Delhi-NCR.

The GRAP restrictions were earlier revoked on January 18, after the air quality improved in the region.

Several flights were delayed at Delhi's Indira Gandhi International (IGI) airport as a layer of fog gripped the national capital.

IMD has predicted moderate fog until January 26 in the National Capital, with foggy conditions expected on January 27 and 28.

While, dense to very dense fog conditions are likely to prevail in the morning over parts of Punjab, Haryana, Chandigarh, and Uttar Pradesh until January 26, the IMD said.