Review of low-cost sensors for indoor air quality: Features and applications

Humans spend the majority of their time indoors, where they are potentially exposed to hazardous pollutants. Within this context, over the past few years, there has been an upsurge of low-cost sensors (LCS) for the measurement of indoor air pollutants, motivated both by recent technological advances and by increased awareness of indoor air quality (IAQ) and its potential negative health impacts. Although not meeting the performance requirements for reference regulatory-equivalent monitoring indoors, LCS can provide informative measurements, offering an opportunity for high-resolution monitoring, emission source identification, exposure mitigation and managing IAQ and energy efficiency, among others. This article discusses the strengths and limitations that LCS offer for applications in the field of IAQ monitoring; it provides an overview of existing sensor technologies and gives recommendations for different indoor applications, considering their performance in the complex indoor environment and discussing future trends

Review of low-cost sensors for indoor air quality: Features and applications

Humans spend the majority of their time indoors, where they are potentially exposed to hazardous pollutants. Within this context, over the past few years, there has been an upsurge of low-cost sensors (LCS) for the measurement of indoor air pollutants, motivated both by recent technological advances and by increased awareness of indoor air quality (IAQ) and its potential negative health impacts. Although not meeting the performance requirements for reference regulatory-equivalent monitoring indoors, LCS can provide informative measurements, offering an opportunity for high-resolution monitoring, emission source identification, exposure mitigation and managing IAQ and energy efficiency, among others. This article discusses the strengths and limitations that LCS offer for applications in the field of IAQ monitoring; it provides an overview of existing sensor technologies and gives recommendations for different indoor applications, considering their performance in the complex indoor environment and discussing future trends

Development of novel methods for extended exposure assessment of combustion-related air pollutants in indoor and outdoor locations

Background & Aims: There is on-going and growing concern regarding acute and chronic human health effects associated with exposure to combustion-related air pollutants. This thesis describes the development and evaluation of novel methods for assessing exposure to combustion-related air pollutants [particulate matter (PM),black carbon (BC) and nitrogen dioxide (NO₂)] in indoor and outdoor environments.Methods: The methods that were developed and evaluated included: mass and darkness/colour analysis of airborne particle samples; passive samplers; portable real time monitors; and GC-MS analysis of particulate-bound polycyclic aromatic hydrocarbons (pPAHs). These methods were used to measure PM, BC and NO₂ in indoor offices and outdoor streets in Glasgow city centre, and an industrial hydraulic fracturing test site in Poland.Results: Detailed evaluation and calibration of novel methods for darkness measurement of low mass particulate material specimens collected on filters were completed to allow subsequent application in BC exposure estimation. Similarly,detailed evaluation allowed the refinement of procedures for field calibration of portable real-time monitors for BC, NO₂ and O₃. Indoor concentrations of PM, BC and NO₂ measured using the calibrated monitoring instruments were influenced by outdoor sources through natural ventilation and the proximity of buildings to urban roadsides. Outdoor measurements at 2 heights indicated that children are likely to experience higher exposures to combustion-related air pollutants from vehicle emissions. Marked elevations of BC and NO₂ concentrations were observed in downwind proximity to industrial fracking equipment sources, where average BC and NO₂ concentrations (11.2 & 111.3 μg/m³) were 2 to 3 times higher than average BC and NO₂ exposures experienced while walking in Glasgow city centre (3.7 & 42.3 μg/m³).Conclusions: Novel exposure science and environmental engineering approaches were developed to allow improved characterisation of short-term to medium-term personal and environmental exposures to combustion-related air pollutants in a wide range of occupational and environmental settings.Keywords: Combustion-related air pollutants; PM; BC; NO₂, novel methods.Background & Aims: There is on-going and growing concern regarding acute and chronic human health effects associated with exposure to combustion-related air pollutants. This thesis describes the development and evaluation of novel methods for assessing exposure to combustion-related air pollutants [particulate matter (PM),black carbon (BC) and nitrogen dioxide (NO₂)] in indoor and outdoor environments.Methods: The methods that were developed and evaluated included: mass and darkness/colour analysis of airborne particle samples; passive samplers; portable real time monitors; and GC-MS analysis of particulate-bound polycyclic aromatic hydrocarbons (pPAHs). These methods were used to measure PM, BC and NO₂ in indoor offices and outdoor streets in Glasgow city centre, and an industrial hydraulic fracturing test site in Poland.Results: Detailed evaluation and calibration of novel methods for darkness measurement of low mass particulate material specimens collected on filters were completed to allow subsequent application in BC exposure estimation. Similarly,detailed evaluation allowed the refinement of procedures for field calibration of portable real-time monitors for BC, NO₂ and O₃. Indoor concentrations of PM, BC and NO₂ measured using the calibrated monitoring instruments were influenced by outdoor sources through natural ventilation and the proximity of buildings to urban roadsides. Outdoor measurements at 2 heights indicated that children are likely to experience higher exposures to combustion-related air pollutants from vehicle emissions. Marked elevations of BC and NO₂ concentrations were observed in downwind proximity to industrial fracking equipment sources, where average BC and NO₂ concentrations (11.2 & 111.3 μg/m³) were 2 to 3 times higher than average BC and NO₂ exposures experienced while walking in Glasgow city centre (3.7 & 42.3 μg/m³).Conclusions: Novel exposure science and environmental engineering approaches were developed to allow improved characterisation of short-term to medium-term personal and environmental exposures to combustion-related air pollutants in a wide range of occupational and environmental settings.Keywords: Combustion-related air pollutants; PM; BC; NO₂, novel methods

Review of low-cost sensors for the ambient air monitoring of benzene and other volatile organic compounds

This report presents a literature review of the state of the art of sensor based monitoring of air quality of benzene and other volatile organic compounds. Combined with information provided by stakeholders, manufacturers and literature, the review considered commercially available sensors, including, PID based sensors, semiconductor (resistive gas sensor) and portable on-line measuring devices (sensor arrays). The bibliographic collection includes the following topics: sensor description, field of application in fixed, mobile, indoor and ambient air monitoring, range of concentration levels and limit of detection in air, model descriptions of the phenomena involved in the sensor detection process, gaseous interference selectivity of sensors in complex VOC matrix, validation data in lab experiments and under field conditions.JRC.C.5-Air and Climat

Two step calibration method for ozone low-cost sensor: Field experiences with the UrbanSense DCUs

Urban air pollution is a global concern impairing citizens' health, thus monitoring is a pressing need for city managers. City-wide networks for air pollution monitoring based on low-cost sensors are promising to provide real-time data with detail and scale never before possible. However, they still present limitations preventing their ubiquitous use. Thus, this study aimed to perform a post-deployment validation and calibration based on two step methods for ozone low-cost sensor of a city-wide network for air pollution and meteorology monitoring using low-cost sensors focusing on the main challenges. Four of the 23 data collection units (DCUs) of the UrbanSense network installed in Porto city (Portugal) with low-cost sensors for particulate matter (PM), carbon monoxide (CO), ozone (O-3), and meteorological variables (temperature, relative humidity, luminosity, precipitation, and wind speed and direction) were evaluated. This study identified post-deployment challenges related to their validation and calibration. The preliminary validation showed that PM, CO and precipitation sensors recorded only unreliable data, and other sensors (wind speed and direction) very few data. A multi-step calibration strategy was implemented: inter-DCU calibration (1st step, for O-3, temperature and relative humidity) and calibration with a reference-grade instrument (2nd step, for O-3). In the 1st step, multivariate linear regression (MLR) resulted in models with better performance than non-linear models such as artificial neural networks (errors almost zero and R-2 > 0.80). In the 2nd step, the calibration models using non-linear machine learning boosting algorithms, namely Stochastic Gradient Boosting Regressor (both with the default and posttuning hyper-parameters), performed better than artificial neural networks and linear regression approaches. The calibrated O-3 data resulted in a marginal improvement from the raw data, with error values close to zero, with low predictability (R-2 similar to 0.32). The lessons learned with the present study evidenced the need to redesign the calibration strategy. Thus, a novel multi-step calibration strategy is proposed, based on two steps (pre and post-deployment calibration). When performed cyclically and continuously, this strategy reduces the need for reference instruments, while probably minimising data drifts over time. More experimental campaigns are needed to collect more data and further improve calibration models