Air pollution is a main challenge in societies with particulate matter PM 2.5 as the major air pollutant causing serious health implications. Due to health and economic impacts of air pollution, low-cost and portable air quality sensors can be vastly deployed to gain personal air pollutant exposure. In this paper, we present an air quality sensing process needed for low-cost sensors which are planned for long-term use. The steps of this process include design and production, laboratory tests, field tests, deployment, and maintenance. As a case study we focus on the field test, where we use two generations of a portable air quality sensor (capable of measuring meteorological variables and PM 2.5 ) to perform an indoor-outdoor measurement. The study found that all of the measurements shown to be consistent through validation among themselves. The sensors accuracy also demonstrate to be adequate by showing similar readings compared to the nearest air quality reference station.

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Low-cost Air Quality Sensing Process: Validation by Indoor-Outdoor Measurements

In many situations or applications, it is essential to evaluate the air quality in relation to human health. For that reason, a monitoring system has been designed with the objective of accurately measuring temporal trends in the air mixture that we breathe. Parameters such as temperature, relative humidity, several inorganic gases (CO2, O3, SO2, CO), the total volatile organic compounds (TVOC) and the concentration of particulate matter need to be measured simultaneously in order to achieve an operational sensing node. With current technology, it is possible to use open-source hardware and software to create a low-cost monitoring system. At present, the development and selection of the hardware, software platforms and the sensors associated with these applications, constitute a scientific and technological interest. The possibility of creating compact, economically accessible systems, based on open-source hardware and software, increases the possibility to perform such analyses at a larger scale and by simple citizens. The proposed system is a prototype in the initial phase, so only the operational capabilities of the system were evaluated during periods of time of 24 and 72 hours of continuous operation, the response of the sensors to step-type inputs and the measurement of background concentrations in urban interior environments.

https://itegam-jetia.org/journal/index.php/jetia/article/download/648/430

Development of a low-cost measuring system for the monitoring of environmental parameters that affect air quality for human health

Air quality in and around ships is governed by a variety of pollution sources that are unique for the shipping context. This makes the living and working conditions on ships substantially different from situations in cities or inside buildings. To gain insight into these differences, information about trends and absolute pollutant amounts on board ships is needed. However, the installation of reference instruments to monitor NO2, NO, O3, particulate matter and other environmental parameters is often not possible because of their size, weight or because of safety reasons. For that reason, more compact devices incorporating a variety of sensors are a good alternative. However, the use of such sensors is only possible when their behaviour and performance in a shipping context are well understood. To study this context, we were allowed to compare sensor-based measurements performed on a 36-year old ship dedicated to near shore operations with measurements of reference-grade instruments. Additional behavioural information of sensors is obtained by measuring campaigns organized on several inland ships. This contribution demonstrates that trends registered by gas and particulate matter sensors are reliable but that insufficient detection limits, higher noise, imperfect calibration and sensor errors result in some reliability constraints.

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Reliability of Lower-Cost Sensors in the Analysis of Indoor Air Quality on Board Ships

Low-cost sensors provide an affordable alternative to monitor environmental parameters with acceptable performance. There is a substantial amount of literature where low-cost sensors are compared with high-end reference measurements. However, not all organizations have access to such reference infrastructure. We propose low-cost calibration methods for temperature, relative humidity, and CO2 to allow them to collect their own reliable data. These methods are based on simple techniques and procedures that allow temperature calibration to be achieved in the range of 0 to 50 °C, relative humidity from 0 to 90%, and CO2 between 0 and 1100 ppm. The materials used to create the calibration setups can be purchased online, at hardware stores, and in pharmacies. The reliability of the calibration methods was evaluated using several indicators, such as the airtightness of the calibration box, similarity with the factory calibration, similarity with the reference, similarity between different sensors, replicability of the calibration method, and the similarity with a golden standard. In addition, the results of the low-cost calibration methods were compared with the more advanced calibration methods. A short measurement campaign in the city of Santa Clara, Cuba, demonstrated that such calibrations transform in-house developed monitoring systems into valid low-cost scientific instruments for decision-making. This work creates opportunities for institutions and researchers hosted in low- and mid-income countries to build and validate their own equipment to reliably solve local problems.

/pdf/a-low-cost-calibration-method-for-temperature-relative-1uk7xcx1.pdf

A Low-Cost Calibration Method for Temperature, Relative Humidity, and Carbon Dioxide Sensors Used in Air Quality Monitoring Systems

Poor air quality is a global problem that affects human health and ecosystems all over the world. For that reason, many countries invest in networks of reference monitoring stations that measure air quality in real time. However, the high installation and maintenance costs of these stations mean that smaller cities or underdeveloped regions are less covered by such stations. In these regions, alternative detection technologies such as low-cost monitoring systems can be used instead. Unfortunately, the results of such monitoring devices are often questioned by academics. This contribution proposes the design of an air quality monitoring system where cost and reliability have been optimized from a hardware point of view. In addition, the device has been coupled to an IoT platform so that inexperienced users can view and share the collected information The design of affordable systems increases the ability to perform ad hoc analysis at the level of neighborhoods or cities by citizen science organizations or governmental entities.

Design of a Low-Cost System for the Measurement of Variables Associated With Air Quality

Low-cost sensor technology can potentially make revolutionary changes in our current air pollution monitoring paradigm in urban areas. However, the widespread adoption of low-cost sensor technology is still not feasible due to a number of limitations regarding sensitivity, accuracy and comparability. In this study we report the results from preliminary laboratory and in-field tests carried out within the TECNAIRE-cM project for commercial NO 2 and O 3 sensors including both, solid-state and electrochemical technologies. The ultimate goal is to understand the current capabilities of this technology and the prospects to incorporate it in both research and routine measurement or urban air quality. We found significant performance differences although none of the devices tested could provide satisfactory results in real-world conditions. We conclude that unit-specific advanced statistical calibration methods are needed to obtain reliable results with the low cost sensors devices in urban areas.

/pdf/low-cost-sensors-for-urban-air-quality-monitoring-4nfplgziaz.pdf

Francisco Javier Gomez

Papers

Low-Cost sensors for urban air quality monitoring: preliminary laboratory and in-field tests within the TECNAIRE-CM project