Delhi: Grap Stage-4 curbs lifted as AQI improves to ‘very poor’

The 24-hour average air quality index (AQI) stood at 378 (very poor) at 4 pm – down from a reading of 410 (severe) at 4pm on Monday

The Commission for Air Quality Management (CAQM) on Tuesday lifted stage-4 of the Graded Response Action Plan (Grap) after the air quality improved marginally. The 24-hour average air quality index (AQI) stood at 378 (very poor) at 4 pm – down from a reading of 410 (severe) at 4 pm on Monday, snapping a three day streak where the AQI had been 400 or higher.

The removal of stage-4 allows the entry of trucks and diesel operated BS-4 Heavy Goods Vehicles (HGVs) in the capital again. (Sunil Ghosh /Hindustan Times)

It was 440 (severe) on Sunday and 400 (very poor) on Saturday.

Forecasts show Delhi’s AQI is now set to remain ‘very poor’ in the coming days, even as a western disturbance approaches, bringing possible light rain and gusty winds on January 23.

“Delhi’s air quality is likely to be in the ‘very poor’ category from January 21 till January 23. The outlook for the subsequent six days – from January 24, shows the AQI will be between ‘very poor’ and ‘poor’ ranges,” said the Air Quality Early Warning System (EWS) for Delhi – a forecasting model under the Centre.

The removal of stage-4 allows the entry of trucks and diesel operated BS-4 Heavy Goods Vehicles (HGVs) in the capital again. It also allows construction and demolition (C&D) activities to resume for linear projects, however private construction and demolition (C&D) activities are still prohibited. The mandatory restriction on schools to conduct hybrid classes between six till 11 (barring 10 and 12) are also lifted.

Further, a restriction set by the Delhi government – on non-Delhi registered vehicles below BS-6 – has also been lifted.

Stage-4 was invoked in the capital on Saturday, January 17, when the day’s AQI began to rise rapidly and crossed 400 in the evening. Typically, stage-4 is invoked when the AQI is expected to cross 450.

The CAQM in a statement on Tuesday said it was lifting the measures given the forecast for “very poor” air, “keeping in view the disruptive nature of restrictions, and “considering the trend of improvement in the average AQI of Delhi”.

Central Pollution Control Board data at 8 am showed that of the 39 active ambient air quality stations in the city, 23 were still in the “severe” category. However, by 7 pm, only five remained in “severe” as winds picked up during the day, allowing dispersion. On Monday, as many as 25 stations were in “severe”, while on Sunday, 33 stations were in the “severe” range.

Data showed Wazirpur was the worst impacted location on Tuesday morning, recording a reading of 445, followed by Anand Vihar (444). On Monday Wazirpur peaked at 473, followed by Vivek Vihar at 472. On Sunday, Anand Vihar peaked at 497 — only three points short of maxing out at 500.

The India Meteorological Department (IMD) has issued a yellow alert for Friday, forecasting chances of very light to light rain. There are also chances of gusty winds up to 40 km/hr during the day.

Delhi meanwhile witnessed shallow to moderate fog on Tuesday morning, with visibility down to 200 metres at Safdarjung. It was 700 metres at Palam. Delhi’s minimum stood at 7.2°C -- around normal for this time of the year. It was 7.7°C on Monday.

The maximum meanwhile stood at 25.7°C – six degrees above normal. It was 26.7°C a day earlier, keeping days unusually warm. The maximum is forecast to hover between 22-24°C on Wednesday and between 24-26°C on Thursday.