The Commission for Air Quality Management on Friday revoked emergency measures under stage 3 of the Graded Response Action Plan in the National Capital Region as the air quality improved due to incessant rainfall.

“Owing to the favourable meteorological conditions and continuous rains since early morning [on Friday], the AQI [air quality index] of Delhi has been continuously improving and has been recorded as 348 at 5.00 PM and 341 at 6.00 PM & 334 at 7.00 PM,” the air quality panel said in a statement on Friday.

However, air pollution control measures under stage 1 and stage 2 of the revised GRAP shall remain in place and be implemented, monitored and reviewed to ensure that the air quality index does not increase again, the statement added.

The GRAP is a set of incremental anti-pollution measures that are triggered to prevent the further worsening of air quality once it reaches a certain threshold in the National Capital Region.

Stage 3 of the emergency measure includes a shutdown of all demolition work as well as mining and stone-crushing activities in the National Capital Region. It also mandates a ban on the operation of Bharat Stage emission standards III petrol and BS IV diesel light motor vehicles in Delhi.

While stage 2 imposes a ban on the use of coal, firewood and diesel generators, except for emergency and essential services, stage 1 includes a temporary halt on construction activities for public projects.

In its statement on Friday, the Commission for Air Quality Management noted that the air quality index in the region was expected to remain in the “poor” category over the next few days.

At 9.05 am on Saturday, the average AQI in Delhi stood at 152, according to data from the Central Pollution Control Board.

An index value between 0 and 50 indicates “good” air quality, between 51 and 100 indicates “satisfactory” air quality and between 101 and 200 indicates “moderate” air quality.

As the air quality deteriorates, the index value increases. A value of 201 and 300 means “poor” air quality while between 301 and 400 indicates “very poor” air.

Between 401 and 450 indicates “severe” air pollution while anything above the 450 threshold is termed “severe plus”. At these levels, healthy people can experience respiratory illnesses from prolonged exposure to air pollution.

On December 16, amid worsening pollution, the air quality panel ordered the implementation of stage 3 and stage 4 of GRAP across the National Capital Region.

Stage 4 is the highest level of GRAP. At this level, all construction activities, even of highways and roads, are banned, and trucks are prohibited from entering the National Capital Region, except if they are carrying essential commodities or running on clean fuels.

Schools for students up to Class 5 had already transitioned to the hybrid mode – or both physical and online classes – in Delhi, Gurugram, Faridabad, Ghaziabad and Gautam Buddh Nagar when the third stage of GRAP was implemented.

The Commission for Air Quality Management also noted in its order that the Supreme Court had on December 5 directed it to reintroduce stage 4 measures if the air quality index were to cross 400.

Also read: Why Delhi’s air crisis needs year-round action – not ad-hoc emergency responses