Faulty air monitors at Mumbai’s construction sites: the government’s air pollution monitoring vans must be deployed now. Awaaz Foundation photographed the displays at construction sites in Bandra and Khar 230 times across 38 days (Mar–May and Sep–Oct 2026). On the 26 days between 23 March and 5 May, we compared each site reading with the Government’s own Kherwadi and BKC station readings on the SAMEER app. For September–October we used the daily AQI (US scale) for Mumbai from aqi.in. What we found: 🔴 PM2.5 of 0 at active sites. On 13 April one monitor showed PM2.5 at 0 while PM10 on the same screen was 34, which is impossible. 🟠 On 16 of the 26 days, at least one monitor showed PM2.5 below 10 µg/m³, well under the WHO’s 15 µg/m³ guideline. Altogether, 37 readings were below 10. ⚠️ On 3 April, when Kherwadi and BKC recorded PM10 of 91 and 133, most monitors showed single digits. ⚫ Monitors were switched off on 7, 10 and 11 April, and on 10 other days at least one display was unreadable. The BMC has said it will fold these readings into its official findings. Unless the data is first certified with calibrated meters, that exercise is meaningless and may mislead the people who rely on it. A wrong number that looks official is worse than no number at all. We urge the authorities to: Calibrate, audit and certify every site monitor before using its data. Publish real-time, time-stamped PM2.5 data online, on a public website that lists all active construction sites along with past data. Act against sites with faulty, switched-off or misleading displays. Use this data in construction monitoring and licensing only after its accuracy has been checked. Urgently deploy the government’s 40 air-pollution monitoring vans, which carry calibrated instruments, to measure air quality at construction sites across the city, starting with the sites where readings are faulty, zero or switched off. Use the vans’ data, not the uncalibrated site monitors, to track local-level pollution until every site monitor has been certified. @Dev_Fadnavis @CMOMaharashtra @mybmc @mpcb_official