The technology associated with low-cost sensors (LCS) to monitor air quality has seen rapid developments over the past few years. While their use becomes more widespread and some are promoting them as silver bullet for air pollution science and control, experts have advised caution.  

It is clear that LCS have a number of benefits, as they render air pollution monitoring less expensive compared to reference instruments thereby allowing their deployment in larger numbers and in remote locations or in places with no other access to monitoring.  

However, as these sensors encompass a wide variety of technologies and are not subject to certification, they are subject to significant biases in their measurements and significant drifts over long periods of operation. In addition, while LCS are relatively cheap to acquire, their maintenance costs can be high, they have relatively short lifetimes and their large measurement biases make them unsuitable to assess air pollution trends. Calibration of LCS can also be a challenge. Hence, accuracy, reliability and reproducibility of different LCS used for measurements of atmospheric composition have to be assessed prior to deployment and use.  

At their annual meeting (6-7 May 2024), experts of the Task Force on Measurements and Modelling, a task Force under the UNECE Convention on Long-range Transboundary Air Pollution, shared information on experiences from both laboratory studies and real-world measurements with LCS. Experiences from different countries have shown that in some cases LCS are unable to capture high concentration pollution events. To help users make sense of the data that low-cost sensors provide, additional tools and calculations as well as co-location with reference monitoring instruments is needed.  

Experts agreed that robust quality assurance performed on the data produced by LCS is of utmost importance. In order to provide guidance to users, some countries have developed best-practice guidance to enable users to select sensor systems appropriate for their monitoring needs, deploy sensors in a way that promotes representative sample collection, and undertake the quality assurance processes needed to generate fit-for-purpose data. Given the speed in which low-cost sensors technology develops, the Task Force will follow developments and discuss the topic further at future meetings.