The overall air quality of Delhi was 'moderate' on Thursday, a significant improvement due to western disturbances, scattered rain and high wind speed, authorities said.According to the Central Pollution Control Board (CPCB) data, the overall air quality index (AQI) of the city was at 171, which falls in the 'moderate' category, a significant drop from the AQI of 349 recorded on Wednesday, which falls in the 'very poor' category.
An AQI between 0 and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and between 401 and 500 'severe'.
The CPCB said 31 areas in the national capital recorded 'moderate' air quality, while four areas had 'poor' quality air. None of the areas recorded 'very poor' or 'severe' air quality.
The level of PM2.5 -- particles in the air with a diameter of less than 2.5 micrometres -- was recorded at 76 and the PM10 level was at 119, it said.
In the National Capital Region, Ghaziabad, Greater Noida, Noida and Gurugram recorded also recorded 'moderate' air quality, the CPCB data stated.
The authorities said the southwesterly winds from the Arabian sea will bring more moisture in the capital.
According to the Centre-run System of Air Quality and Weather Forecasting (SAFAR), "The wind speed is expected to slow down in the coming days which will deteriorate the air quality to poor after two days. The AQI will remain moderate on Friday also."