New Delhi, Jan 22 (PTI) Delhi's air quality rapidly deteriorated to the severe category on Sunday, but the Commission for Air Quality Management (CAQM) chose not to invoke curbs under stage-III of the Graded Response Action Plan in view of a prediction of "immediate improvement".
The action plan is a set of anti-air pollution measures followed in the national capital and its vicinity according to the severity of the situation.
Delhi's 24-hour average air quality index (AQI) stood at 407 on Sunday, worsening from 294 on Saturday, amid calm winds.
The stable atmospheric conditions allowed accumulation of pollutants from highly localised sources, such as a fire in central Delhi on Saturday, an official of the India Meteorological Department (IMD) said.
In a statement, the CAQM said the sub-committee responsible for invoking action under the Graded Response Action Plan (GRAP) took stock of the situation at a meeting on Sunday.
It noted that the sudden and steep dip in air quality in the region is an "aberration as the forecasts predict immediate improvement with the overall AQI to move into 'very poor' category from tonight itself", the statement said.
According to the IMD and the Indian Institute of Tropical Meteorology, Delhi's AQI is likely to fluctuate largely between 'poor' and 'very poor' categories in the coming days.
"After comprehensively reviewing the air quality scenario and other relevant aspects, the sub-committee decided that the ongoing action under stage-I and stage-II of GRAP shall continue and it is not considered necessary to invoke stage-III at this moment," the CAQM said.
The GRAP classifies the air quality in Delhi-NCR under four different stages: stage-I -- 'poor' (AQI 201-300); stage-II -- 'very poor' (AQI 301-400); stage-III -- 'severe' (AQI 401-450); and stage-IV -- 'severe plus' (AQI>450).
If the AQI is projected to reach the 'severe' category, restrictive actions under stage-III are to be invoked at least three days in advance. These include a ban on non-essential construction and demolition, closure of stone crushers and mining activities in the region.
Non-polluting activities such as plumbing, carpentry, interior decoration and electrical work are allowed.
The next stage -- 'severe plus' category or stage-IV -- includes steps like a ban on the entry of trucks into Delhi, allowing 50 per cent of staff to work from home in public, municipal and private offices, closure of educational institutions and the plying of vehicles on an odd-even basis. PTI GVS ANB ANB