One city, two data: Controversy between CPCB and IQAir on Delhi air quality, experts confused - Delhi air quality differs cpcb vs iqair data

Updated: Thu, 23 Oct 2025 01:04 (IST) There is a discrepancy in the data of CPCB and IQAir regarding the air quality of Delhi. According to CPCB, the AQI is ‘weak’, while IQAir calls it ‘very weak’. Experts believe that this discrepancy is due to differences in measurement methods, causing confusion among the public. Both organizations consider Delhi’s air quality to be of concern. State Bureau, New Delhi. Confusion has arisen over Delhi’s air quality data. The Central Pollution Control Board (CPCB) gives some AQI while international platforms like the Swiss company IQ Air give something else. For example, on Wednesday, CPCB reported Delhi’s AQI as 353 while IQ Air showed 253. AQI in Delhi has remained around 350 for the past three days. The smoke and dust after Diwali engulfed the entire city. Residents experience eye irritation and breathing problems. Meanwhile, confusion has arisen over Delhi’s air quality data. CPCB shows AQI below 400, while IQ Air shows below 300. IQ Air numbers were much higher on Diwali. For example, at 12:30 pm on Diwali evening, CPCB recorded an AQI of 272 at Siri Fort, while IQ Air recorded 2,449. This disparity highlights the uncertainty about the actual AQI in Delhi-NCR. Environmentalists say the figures from both CPCB and IQ Air are technically correct as they use different measurement methods and scales. Dr Mohan P. George, former additional director of Delhi Pollution Control Committee (DPCC), says, AQI is based on six main parameters – PM 2.5, PM 10, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. Its scale ranges from 0 to 500. Any level above 400 is considered ‘severe’. In contrast, IQ Air follows the American model. Remove ads Read news only The index also ranges from 0 to 500, but it reports figures above 500 as extremely dangerous. In India, levels above 500 are considered ‘virtually useless’ as they already indicate serious health risks. The large variation in Delhi’s AQI figures comes mainly from the sources and instruments of the data. CPCB uses analyzer-based reference grade machines, which are scientifically calibrated (standardized). In contrast, IQ uses sensor-based devices, which are low-cost and whose calibration procedures and algorithms (calculation methods) are not public. Dr George said: ‘I trust CPCB’s data more because their monitoring methods and standards are transparent, while IQ Air’s algorithm is secret.’ However, despite these differences, experts agree that both the platforms highlight the dire state of Delhi’s air quality, showing that PM 2.5 levels are well above the dangerous limit. Variation in AQI of some areas of Delhi on Wednesday Zone CPCB IQ Air Dwarka-III 366 237 Punjabi Bagh 387 263 Sirifort 364 210 Anand Vihar 427 352 RK Puram 397 322