Breathe London created a network of 100 state-of-the-art sensors and began driving two specially equipped Google Street View cars through the capital to measure air pollution. The graphic shows Breathe London fixed monitors near 3 schools. This shows 55 to 75% variation within 24 hours on a summer day!
Delhi reported the following for a moderate AQI day 19 March 2019. PMI2.5 AQI (the linear index based on concentration) varied from an average of 183 to a low of 35 (-81%) and a high of 318 (+74%). The situation on a very poor AQI day of 13 Nov 2018 was an average PMI2.5 of 371 over 100% higher mean then the moderate March day.