Investigation of low cost sensors for particulate matter and gases for the application in measuring the ambient air quality
Creators: name: Samad, Abdul
name: Vogt, Ulrich
name: Laquai, Bernd
name: Surgaylo, Anastasia
name: Solis Castillo, Grecia Carolina
Publisher: name: Zenodo
Year: 2023
Subjects: Ambient Air Quality, Low cost sensors, Particulate matter, NO, NO2, O3, CO

description: Exposure to outdoor air pollution is linked to premature mortality and to several illnesses in humans; however, not only humans are affected, but also vegetation and wildlife. In this context, monitoring of air pollution has become more relevant in urban areas nowadays. As a result, several air quality control programs, government institutions and municipalities have implemented stationary air monitoring stations around the world. The deployment of those stations is costly and time-consuming and for that reason they are only installed in hot spots. Nevertheless, if the goal is to catch the spatial and temporal concentration of air pollutants, tens or hundreds of this equipment should be deployed along the cities. To solve that problem, several companies have been developing low cost sensors, which are attached to an electronic platform and serve as an alternative to implement them in more hot spot locations. Those sensors are renowned for being cost-effective, portable and having a big potential for air quality applications. In contrast, there are some uncertainties in the data obtained by low cost sensors that can influence the final results of the air quality measurements. Therefore, a detailed investigation is necessary in order to implement these sensors for ambient air quality measurements.<br> This study focused on investigating different air quality sensors available in the market. After finding the best sensors available, a platform unit was built containing air quality sensors for Particulate Matter (PM) and gaseous pollutants such as nitrogen oxides (NO and NO<sub>2</sub>), ozone (O<sub>3</sub>) and carbon monoxide (CO). Separate platforms were built for PM and gaseous pollutants. The platforms were then tested in the laboratory for the known influences such as change in temperature, humidity. The gas sensors were also tested for the interferences with other gases.<br> For the PM measurement platform comparative measurements with professional aerosol spectrometer were performed in the laboratory as well as in the field. A concept was developed to reduce the uncertainty of the sensor results and increase the data quality. First simple correction approaches have shown that this can improve the deviation of the measurement results of the sensors with each other and in comparison to the aerosol spectrometers. For the gas sensor platform, different experiments were carried out such as the influence of the warming up of the sensors, the relevance of using a pump in the sensor box, the behavior of the sensor signals considering changes in the relative humidity (20%, 30%, 40%, 50% and 60%), the behavior of the sensors during changes in temperatures (20°C, 30°C and 40°C) and the interferences with other gases. These sensors were then installed in the field for the air quality measurements and were compared with professional measurement devices. The results obtained from this project indicate that the changes in humidity is the most relevant factor that affect the data obtained from the low cost sensors in comparison to the others factors evaluated in this investigation. In consequence, this study presents alternatives to avoid this problem and to compensate the changes. According to the findings of this work, it can be claimed that some of the low cost air quality sensors available in the market have the potential to be used for measuring air quality after the application of quality assurance measures and also the creation of a stationary air quality measurement platform to enable high spatial distribution and temporal resolution.<br> This work was performed under the project Urban Climate Under Change [UC]² funded by the Federal Ministry of Education and Research (BMBF) Germany.