Review of the Performance of Low-Cost Sensors for Air Quality Monitoring

Federico Karagulian,Nathalie Redon,Alexander Kotsev,Laurent Spinelle,Friedrich Lagler,Maurizio Barbiere,Michel Gerboles,Sabine Crunaire,Annette Borowiak

doi:10.3390/atmos10090506

Abstract

A growing number of companies have started commercializing low-cost sensors (LCS) that are said to be able to monitor air pollution in outdoor air. The benefit of the use of LCS is the increased spatial coverage when monitoring air quality in cities and remote locations. Today, there are hundreds of LCS commercially available on the market with costs ranging from several hundred to several thousand euro. At the same time, the scientific literature currently reports independent evaluation of the performance of LCS against reference measurements for about 110 LCS. These studies report that LCS are unstable and often affected by atmospheric conditions—cross-sensitivities from interfering compounds that may change LCS performance depending on site location. In this work, quantitative data regarding the performance of LCS against reference measurement are presented. This information was gathered from published reports and relevant testing laboratories. Other information was drawn from peer-reviewed journals that tested different types of LCS in research studies. Relevant metrics about the comparison of LCS systems against reference systems highlighted the most cost-effective LCS that could be used to monitor air quality pollutants with a good level of agreement represented by a coefficient of determination R2 > 0.75 and slope close to 1.0. This review highlights the possibility to have versatile LCS able to operate with multiple pollutants and preferably with transparent LCS data treatment.

Highlights

The increase of the commercial availability of micro-sensor technology is contributing to the rapid adoption of low-cost sensors for air quality monitoring by both citizen science initiatives and public authorities [1]
The data set of R2 for calibration is limited in size, we have investigated if the type of calibration has an influence on the agreement between calibrated low-cost sensors (LCS) data and reference measurements
The method used for the calibration of LCS is generally considered confidential information by the majority of LCS manufacturers and little information can be found about the calibration of LCS that fall under the category “black box” compared to the ones that fall under the category “open source”

Summary

Introduction

The increase of the commercial availability of micro-sensor technology is contributing to the rapid adoption of low-cost sensors for air quality monitoring by both citizen science initiatives and public authorities [1]. Public authorities want to increase the density of monitoring and measurements and often want to rely on low-cost sensors because they cannot afford sufficient reference air quality monitoring stations (AQMS) [2]. Low-cost sensors can provide real time measurements at lower cost, allowing higher spatial coverage than the current reference methods for air pollutant measurements. Plenty of institutes in charge of air quality monitoring for regulatory purposes, as well as local authorities, are considering including low-cost sensors among their routine methods of measurements to supplement monitoring with reference measurements. The lack of exhaustive and accessible information in order to compare the performance of low-cost sensors and the wide commercial offerings make it difficult to select the most appropriate low-cost sensors for monitoring purposes

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Conclusion