New Delhi: A new study revealed that pollutant concentration readings of air quality sensors differ not only between manufacturers but also among devices from the same manufacturer.
In some cases, the air quality sensors, also called low-cost sensors (LCSs), showed inconsistent or faulty readings over time, raising concerns about long-term reliability, according to the analysis.
LCSs have gained prominence in developing countries such as India in recent years as they offer an affordable and promising way to expand pollution monitoring. However, readings from these sensors vary widely unless properly calibrated for local conditions.
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, Center for Study of Science, Technology and Policy (CSTEP), and released on Thursday.
It involved examining 48 multi-pollutant sensor devices from six different manufacturers that supply sensors commercially in India. The evaluation was done before these LCSs became part of a multi-pollutant sensor network across urban Bengaluru.
The sensors were placed next to a reference monitor and observed for up to eight months to check their durability and reliability.
As part of the study, readings were taken for particulate matter (PM2.5 and PM10), nitrogen dioxide, ozone and carbon monoxide.
“Overall, the initial evaluation (four to six weeks of observation) indicated that manufacturer-reported sensor data can vary substantially between devices and across manufacturers, particularly when compared with data from reference instruments,” said the study.
In the medium-term evaluation (about eight months of observation), several sensors either stopped working or gave wrong readings.
These issues may have emerged because the manufacturers calibrated the sensors according to different environmental conditions and a different mix of pollutants.
When the study’s authors calibrated these sensors according to Bengaluru’s local conditions, the devices performed significantly better.
“Given this, it is recommended that low-cost sensors must be calibrated before deployment. As environmental factors such as weather and pollution patterns differ from place to place, calibration models should reflect these realities to ensure accurate readings,” said the study.
It also recommended that because sensor accuracy declines with use and calibration may become outdated due to changing conditions, the devices should go through regular performance checks, ideally every three to six months. PTI
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