A new evaluation of low‑cost air quality sensors used in Indian cities has found that their pollutant readings can differ widely between manufacturers and even between devices from the same brand, underscoring the need to calibrate each sensor for local weather and pollution patterns before deployment. The study, “Performance Evaluation of Multi‑pollutant Air Quality Sensors at Indi‑SET, Bengaluru, India, First Edition; A Short‑ and Medium‑Term Evaluation,” was carried out by the Bengaluru‑based think tank Centre for Study of Science, Technology and Policy (CSTEP) and released this week.
The analysis examined 48 multi‑pollutant sensor units from six different manufacturers commonly deployed in India, placing them next to a reference‑grade air‑quality monitor and observing them for up to eight months. The devices measured key pollutants including PM2.5, PM10, nitrogen dioxide, ozone and carbon monoxide, and the study found that manufacturer‑provided calibration data often produced readings that varied substantially from the reference instrument, especially over time. Some sensors either stopped working entirely or began delivering clearly inaccurate values, raising concerns about long‑term reliability in public‑health and policy‑making applications.
Researchers linked the discrepancies to the fact that manufacturers often calibrate sensors under different environmental conditions and pollutant mixtures than those found in Indian cities such as Bengaluru. When the team recalibrated the devices using local conditions specific to Bengaluru, performance improved markedly, reinforcing the importance of city‑ or region‑specific calibration models. The study therefore recommends that low‑cost sensors always be calibrated before rollout and that their accuracy be rechecked every three to six months, as sensor drift and changing environmental conditions can render earlier calibration settings obsolete.
