The air quality improved to "moderate" category across Noida, Greater Noida, Ghaziabad, Faridabad and Gurgaon on Friday, a government agency said.
The presence of pollutant PM 2.5 and PM 10 although remained high in the five immediate neighbours of Delhi, according to the air quality index (AQI) maintained by the Central Pollution Control Board (CPCB).
According to the index, an AQI between zero and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.
The average 24-hour AQI at 4 pm on Friday was 107 in Gurgaon, 125 in Noida, 129 in Greater Noida, 134 in Faridabad and 166 in Ghaziabad and Noida, 296 in Greater Noida, the CPCB's Sameer app showed.
On Thursday, it was 301 in both Ghaziabad and Noida, 296 in Greater Noida, 312 in Faridabad and 299 in Gurgaon.
It was 444 in Ghaziabad, 414 in Noida, 394 in Greater Noida, 348 in Faridabad and 299 in Gurgaon on Wednesday.
On Tuesday, the AQI was 428 in Ghaziabad, 396 in Noida, 382 in Greater Noida, 360 in Faridabad and 296 in Gurgaon.
On Monday, it was 365 in Ghaziabad, 301 in Noida, 286 in Greater Noida, 285 in Gurgaon and 272 in Faridabad.
The CPCB states that an AQI in the "moderate" category may cause breathing discomfort to the people with lung, asthma and heart diseases.
The AQI for each city is based on the average value of all stations there. Noida, Faridabad and Ghaziabad have four stations each, while Gurgaon has three and Greater Noida two, according to the app.