Government-backed air quality monitoring apps like SAFAR and SAMEER top out at 500 - the upper limit of India's AQI (air quality index) scale, which converts complex data on various pollutants such as PM2.5, PM10, nitrogen dioxide, sulphur dioxide, carbon monoxide and ozone, into a single number. But private and international trackers such as IQAir and open-source monitoring platform AQI routinely show far higher numbers, often shooting past 600 and even crossing 1,000 on some days. This contrad