Delhi's air quality remained in the 'very poor' category due to slow wind speed and high humidity on Monday, authorities said.
The overall air quality index (AQI) was recorded at 322, which comes under the 'very poor' category, according to the Central Pollution Control Board (CPCB) data.
Fourteen areas in Delhi recorded 'very poor' air quality and 14 recorded 'poor' air quality, it said.
On Monday, the PM2.5 -- particles in the air with a diameter of fewer than 2.5 micrometres -- level was recorded at 167, while the PM10 level was recorded at 307, according to CPCB data.
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 401 and 500 'severe'.
Air quality is 'very poor' and is expected to remain in the same category with the gradual increase for the next three days as wind speed is slow and humidity is high which is unfavourable, the Centre-run System of Air Quality and Weather Forecasting (SAFAR) said.
"Fire counts from stubble burning declined significantly and hence have a negligible impact," it said.