Real-time Monitoring Instrument Research Articles

Smart Home Powered by Solar: IoT-based SEPIC Converter Control

Background: In this article, an IOT solution for managing and controlling a PV system with applications for the home is presented. A DC-DC SEPIC converter, a bidirectional converter, a PWM generator, and a single-phase voltage source inverter with active clamping are used for power conditioning. An output voltage control loop is implemented, and real-time online communication with an internet server is accomplished using the PIC microcontroller. Methods: The ESP8266MOD WIFI IOT module works with the Blynk mobile app. Experimental findings showing the proper operation of IOT features demonstrate the effectiveness of voltage regulation. In this article, frequency is taken into consideration as solar power is integrated with the grid. A user may easily control the DC-DC converter, load batteries, and monitor battery voltage through our userfriendly GUI interface. Results: In this paper, an IOT (Internet of Things) application was used to control and track the output of a modest PV power plant. The study shows the efficiency of the digitally controlled system developed to regulate the output voltage of the SEPIC DC-DC converter. Practical Significance: They further argue that the ESP8266 and microcontroller's versatility make them an appropriate instrument for remote and real-time monitoring and control of the proposed model from around the world. The energy that is produced by the sun is added to the grid so that it may be put to effective use and contribute to satisfying the rising demand for energy. Solar energy is the input that SEPIC uses to charge the batteries and for all of its other processes. In the event that solar photovoltaic (PV) panels are not available, the SEPIC DC-DC converter will derive its energy from AC power. Conclusion: In this article, an IOT (Internet of Things) application was used to control and track the output of a modest PV power plant. The research demonstrates the effectiveness of the digitally controlled system created to manage the output voltage of the SEPIC DC-DC converter. They further argue that the ESP8266 and microcontroller's versatility make them an appropriate instrument for allowing remote and real-time monitoring and control of the proposed model from any part of the world. The energy that is produced by the sun is added to the grid so that it may be put to effective use and contribute to satisfying the rising demand for energy. Solar energy is the input that SEPIC uses to charge the batteries and for all of its other processes. In the event that solar photovoltaic (PV) panels are not available, the SEPIC DC-DC converter will derive its energy from AC power.

A case study evaluating the performance of a cost-effective optical particle counter coupled with a humidity compensation approach for ambient air monitoring of particulate matter

The spatial monitoring of submicron particles has become an essential issue due to their negative effects on human health. However, the use of high-cost and high-grade measurement instruments is a challenging investment cost. Thus, a cost-effective optical particle counter (OPC), which is improved measurement quality, has become a good candidate. In this study, two cost-effective OPCs, coupled with a heated inlet tube to reduce the effect of humidity on its measurements, were applied in the field to measure ambient PM10, PM2.5, and PM1 over 1 month. Their 1-h-average and 24-h-average data were compared with those obtained from a reference-grade OPC and a beta attenuation monitor (BAM). In particular, the correlations between the measurement data obtained from them, the differences in the mean values of these data, and the relative errors were evaluated. The PM2.5 data obtained from cost-effective OPCs were comparable to those from BAM at even under high humidity conditions, except for rainy days. The data obtained from the cost-effective OPCs also showed good correlations and low relative errors (i.e., < 7%) compared to the reference-grade OPC, with no significant difference in mean values in terms of the PM2.5 and PM1 data. Although the measurement of PM10 by the cost-effective OPCs showed lower quality than PM2.5 and PM1, the relative errors were still acceptable (i.e., < 18%) compared with those in other studies. Therefore, the cost-effective OPC coupled with a heated inlet tube has the potential to serve as a real-time monitoring instrument for ambient PM2.5 and PM1.

Air Pollution inside Vehicles: Making a Bad Situation Worse.

Thailand has successfully forwarded Article 8, Protection from Exposure to Tobacco Smoke, of the World Health Organization's Framework Convention on Tobacco Control (WHO FCTC). It achieved its 100% smoke-free goals in public places in 2010, next pursuing other bans in outdoor places to lower particulate matter air pollution (PM2.5). Our aim was to expose the secondhand smoke levels in vehicles since SHS is a danger to everyone, but especially to children and youth. This is the first experimental study of its kind in Thailand. We measured PM2.5 for 20 min under four conditions in 10 typical Thai vehicles, including commonly used sedans and small pickup trucks. We used an established protocol with two real-time air monitoring instruments to record PM2.5 increases with different vehicle air exchange and air conditioning conditions. Monitoring was recorded in the vehicle's front and back seats. The most common Thai ventilation condition is all windows closed with fan/air conditioning (AC) in operation because of Thai tropical conditions. Mean exposure levels were three and nearly five times (49 and 72 μg/m3) the 24 h WHO standard of 15 μg/m3 in the back and front seats, respectively. These high PM2.5 exposure levels warrant action to limit vehicle smoking for public health protection.

Two-dimensional fluorescence excitation spectroscopy: A novel technique for monitoring excited-state photophysics of molecular species with high time and frequency resolution.

We propose a novel UV/Vis femtosecond spectroscopic technique, two-dimensional fluorescence-excitation (2D-FLEX) spectroscopy, which combines spectral resolution during the excitation process with exclusive monitoring of the excited-state system dynamics at high time and frequency resolution. We discuss the experimental feasibility and realizability of 2D-FLEX, develop the necessary theoretical framework, and demonstrate the high information content of this technique by simulating the 2D-FLEX spectra of a model four-level system and the Fenna-Matthews-Olson antenna complex. We show that the evolution of 2D-FLEX spectra with population time directly monitors energy transfer dynamics and can thus yield direct qualitative insight into the investigated system. This makes 2D-FLEX a highly efficient instrument for real-time monitoring of photophysical processes in polyatomic molecules and molecular aggregates.

Noninvasive Human Ballistocardiography Assessment Based on Deep Learning

Ballistocardiography (BCG) is a vibration signal of human cardiac activity, which can be obtained by optical fiber sensor in a non-invasive way. The proposed optical fiber sensor as a low power consumption, non-contact, non-invasive real-time health monitoring instrument, has been developed into an effective health care monitoring method. However, when people need to monitor BCG for a long time, a large number of BCG data needs to be collected, which is time-consuming, costly and labor-intensive. To solve this problem, in this paper, we proposed a novel deep learning model, termed BCGNET. Firstly, convolutional neural network (CNN) is used to extract the short-term dependence between multivariate loads. Then, the recurrent neural network (RNN) model is used to capture the long-term dependence of load sequence, and the ultra-long-term repetitive pattern of load sequence is fully studied by using the long-short term memory network with recurrent-skip. Finally, autoregressive layer and full connection layer are used for combined prediction. Extensive experimental results demonstrate the superiority of BCGNET, the accuracy is 91.43% achieved by the proposed BCGNET compared with CNN (89.61%), RNN (89.88%) and multi-head attention network (MHA-Net) (90.22%), and also show the proposed model has good performance in BCG prediction and assessment.

Characterization of an Electronic Nicotine Delivery System (ENDS) Aerosol Generation Platform to Determine Exposure Risks

Evaluating vaping parameters that influence electronic nicotine delivery system (ENDS) emission profiles and potentially hazardous exposure levels is essential to protecting human health. We developed an automated multi-channel ENDS aerosol generation system (EAGS) for characterizing size-resolved particle emissions across pod- and mod-type devices using real-time monitoring instruments, an exposure chamber, and vaping parameters including different ventilation rates, device type and age, e-liquid formulation, and atomizer setup. Results show the ENDS device type, e-liquid flavoring, and nicotine content can affect particle emissions. In general, pod-type devices have unimodal particle size distributions and higher number emissions, while mod-type devices have bimodal size distributions and higher mass emissions. For pod-type devices, later puff fractions emit lower aerosols, which is potentially associated with the change of coil resistance and power during ageing. For a mod-type device, an atomizer with a lower resistance coil and higher power generates larger particle emissions than an atomizer with a greater resistance coil and lower power. The unventilated scenario produces higher particle emission factors, except for particle mass emission from pod-type devices. The data provided herein indicate the EAGS can produce realistic and reproducible puff profiles of pod- and mod-type ENDS devices and therefore is a suitable platform for characterizing ENDS-associated exposure risks.

Characteristics of volatile organic compounds and secondary organic aerosol pollution in different functional areas of petrochemical industrial cities in Northwest China

The aim of this study was to better understand the characteristics of volatile organic compounds (VOCs) and secondary organic aerosol (SOA) pollution in different functional areas of petrochemical industrial cities. In Lanzhou, a typical petrochemical industrial city in Northwest China, with the use of an Integrated Atmospheric Mobile Monitoring Vehicle (IAMMV), various real-time online monitoring instruments, including a VOC monitoring instrument (TH-300B) and single-particle aerosol mass spectrometer (SPAMS), were used in combination. These instruments were employed to determine PM2.5, VOCs and other factors at monitoring sites in Xigu (XG) and Chengguan (CG) districts in September 2020 and 2021, respectively. The results revealed that during the monitoring period, the average VOC concentrations at the XG and CG monitoring sites were 102.3 and 35.8 ppb, respectively. Benzene (45.58 %) and toluene (24.47 %) significantly contributed to the SOA formation potential at the XG site. M/P-xylene (27.88 %) and toluene (23.64 %) more notably contributed to the SOA formation potential at the CG site. The PM2.5 mass concentration at the XG site (24.1 μg·m−3) was similar to that at the CG site (21.2 μg·m−3), but the proportion of particulate matter components greatly differed. The proportion of organic carbon (OC) at the XG site (19.00 %) was higher than that at the CG site (9.97 %). The number of particles containing C2H3O+ (m/z = 43) accounted for 36.96 % and 15.41 % of the total particles at the XG and CG sites, respectively. The mixing ratios of OC and hybrid carbon (OCEC) with C2H3O+ (m/z = 43) were 0.81 and 0.53, respectively, at the XG site and reached only 0.48 and 0.25, respectively, at the CG site. The secondary ageing degree of particles in XG district was high. These results could provide a reference for ambient air quality improvement and the formulation of governance measures in different functional areas of petrochemical industrial cities.

Cost-Effective, Single-Frequency GPS Network as a Tool for Landslide Monitoring.

The constant monitoring of active landslides, particularly those located in the proximity of populated areas or touristic places, is crucial for early warning and risk-management purposes. The commonly used techniques deploy expensive instrumentation that can be hardly afforded, especially by small mountain communities in which landslide events often occur repeatedly. In recent years, the scientific community, as well as the private sector, have devoted growing effort to reducing the costs of monitoring systems. In this work, we present a monitoring network based on single-frequency Global Positioning System (GPS) sensors that have been activated to monitor an active landslide in the Carnic Alps, North-Eastern Italy. The system, which was composed of 12 single-frequency GPS stations, one seismometric station coupled with a single-frequency GPS instrument for real-time monitoring, and one permanent dual-frequency GPS station located in a stable area, provided daily reports of the landslide motion to the local authorities and administration. We show that this system is a valuable, flexible, and cost-effective tool for quick landslide characterization, and has high potential to be used as a landslide early warning system in case of emergency situations.

Real-time streaming tomographic reconstruction with on-demand data capturing and 3D zooming to regions of interest.

Complex dynamic tomographic experiments at brilliant X-ray light sources require real-time feedback on the sample changes with respect to environmental conditions, selecting representative regions of interest for high-resolution scanning, and on-demand data saving mechanisms for storing only relevant projections acquired by fast area detectors and reducing data volumes. Here the implementation details of a 3D real-time imaging monitoring instrument, with zooming to a volume of interest with easy-to-use visualization via ImageJ, a tool familiar to most beamline users, is presented. The instrument relies on optimized data flow between the detector and processing machines and is implemented on commodity computers. The instrument has been developed at beamline 2-BM of the Advanced Photon Source, where the automatic lens changing mechanism for zooming is implemented with an Optique Peter microscope. Performance tests demonstrate the ability to process more than 3 GB of projection data per second and generate real-time 3D zooming with different magnification. These new capabilities are essential for new APS Upgrade instruments such as the projection microscope under development at beamline 32-ID. The efficacy of the proposed instrument was demonstrated during an in situ tomographic experiment on ice and gas hydrate formation in porous samples.

Ultrafine aerosol transient phase measurement with real-time monitoring instrument applied to cleaning process of L-Pbf machine

Ultrafine aerosol transient phase measurement with real-time monitoring instrument applied to cleaning process of L-Pbf machine

Using Real-Time Area VOC Measurements to Estimate Total Hydrocarbons Exposures to Workers Involved in the Deepwater Horizon Oil Spill.

The objective was to present a method that used real-time volatile organic compounds (VOCs) area measurements transformed to daily total hydrocarbons (THC) time-weighted averages (TWAs) to supplement THC personal full-shift measurements collected using passive charcoal badges. A second objective was to develop exposure statistics using these data for workers on vessels piloting remotely operated vehicle (ROV) vessels and other marine vessels (MVs) not at the job title level, but at the vessel level. From hourly vessel averages derived from ~26 million real-time VOC measurements, we estimated full-shift VOC TWAs. Then, we determined the relationship between these TWAs and corresponding full-shift THC personal measurements taken on the same vessel-day. We used this relationship to convert the full-shift VOC measurements to full-shift 'THC' TWA estimates when no personal THC measurements existed on a vessel-day. We then calculated arithmetic means (AMs) and other statistics of THC exposures for each vessel. The VOC-derived estimates substantially supplemented the THC personal measurements, with the number of vessel-days for which we have exposure estimates increasing by ~60%. The estimates of the AMs are some of the highest observed in the GuLF STUDY. As expected, the AMs decreased over time, consistent with our findings on other vessels. Despite the inherent limitations of using real-time area measurements, we were able to develop additional daily observations of personal THC exposures for workers on the ROV vessels and other MVs over time. The estimates likely resulted in more representative estimates of the AMs in the GuLF STUDY. The method used here can be applied in other occupational settings and industries for personal exposure estimation where large amounts of area measurements and more limited numbers of personal measurements are available.

The Influence of Traffic-Related Air Pollution (TRAP) in Primary Schools and Residential Proximity to Traffic Sources on Histone H3 Level in Selected Malaysian Children.

This study aimed to investigate the association between traffic-related air pollution (TRAP) exposure and histone H3 modification among school children in high-traffic (HT) and low-traffic (LT) areas in Malaysia. Respondents’ background information and personal exposure to traffic sources were obtained from questionnaires distributed to randomly selected school children. Real-time monitoring instruments were used for 6-h measurements of PM10, PM2.5, PM1, NO2, SO2, O3, CO, and total volatile organic compounds (TVOC). Meanwhile, 24-h measurements of PM2.5-bound black carbon (BC) were performed using air sampling pumps. The salivary histone H3 level was captured using an enzyme-linked immunosorbent assay (ELISA). HT schools had significantly higher PM10, PM2.5, PM1, BC, NO2, SO2, O3, CO, and TVOC than LT schools, all at p < 0.001. Children in the HT area were more likely to get higher histone H3 levels (z = −5.13). There were positive weak correlations between histone H3 level and concentrations of NO2 (r = 0.37), CO (r = 0.36), PM1 (r = 0.35), PM2.5 (r = 0.34), SO2 (r = 0.34), PM10 (r = 0.33), O3 (r = 0.33), TVOC (r = 0.25), and BC (r = 0.19). Overall, this study proposes the possible role of histone H3 modification in interpreting the effects of TRAP exposure via non-genotoxic mechanisms.

Catalogue of real-time instrumentation and monitoring techniques for tailings dams

ABSTRACT With ongoing catastrophic mine tailings dam failures, the hindsight revelation of poor safety records, and an increasing prevalence of public scrutiny and attention of mining operations, there is an immediate call for enhanced safety of tailings dams. Today, challenges arise in identifying and utilising the ability of monitoring systems to understand the complex performance and behaviours of these dams, reflecting on the system’s ability to predict deterioration before failure occurs. New literature, mining regulators, insurance firms, and mining practitioners are calling for increased diligence in the form of real-time monitoring: but what can the industry offer in response? This research establishes a centralisation of real-time monitoring instruments suitable for tailings dams, discussing the specifications, advantages, and disadvantages of each. An understanding of traditional instrumentation, online monitoring systems, and the value of centralised monitoring was detailed. Collaboration with suppliers discovered innovative systems which enable monitoring of different failure modes and mechanisms.

Assessment of myocardial viability using a minimally invasive laser Doppler flowmetry on pig model

The intra-operative real-time assessment of tissue viability can potentially improve therapy delivery and clinical outcome in cardiovascular therapies. Cardiac ablation therapy for the treatment of supraventricular or ventricular arrhythmia continues to be done without being able to assess if the intended lesion and lesion size have been achieved. Here, we report a method for continuous measurements of cardiac muscle microcirculation to provide an instrument for real-time ablation monitoring. We performed two acute open chest animal studies to assess the ability to perform real-time monitoring of creation and size of ablation lesion using a standard RF irrigated catheter. Radiofrequency ablation and laser Doppler were applied to different endocardial areas of alive open-chest pig. We performed two experiments at three different RF ablation energy setting and different ablation times. Perfusion signals before and after ablation were found extensively and distinctively different. By increasing the ablation energy and time, the perfusion signal was decreasing. In vivo assessing the local microcirculation during RF ablation by laser Doppler can potentially be useful to differentiate between viable and nonviable ablated beating heart in real time.

Field evaluation of in-service buried pipeline using robust instrumentation

In-depth field instrumentation was undertaken on a section of a large diameter (660 mm) cast iron water pipe in Sydney, Australia to monitor the performance of a field pipeline under internal and external loads. This paper elaborates the instrumentation details and procedures adopted to capture various infield data to support the condition assessment of buried ageing pipelines under operational conditions including internal water pressure and external traffic loads. The adopted instrumentation realistically captured pipe strain, pipe joint displacement and rotation, soil pressure, temperature and moisture content. The results are discussed to evaluate the efficiency of the instrumentation for real-time monitoring which facilitates the understanding of the behaviour of a field pipeline. The pipe strains measured under various traffic conditions provide useful estimations for the evaluation of the condition of ageing pipelines. Fairly uniform strains were detected under internal water pressure loadings which showed a considerably larger impact on pipe performance than that due to other influential factors. The soil vertical and lateral pressures measured at various locations around the pipe revealed the relative magnitudes of ground stresses, facilitating new designs and the failure assessment of in-service buried pipelines. Soil moisture and temperature data showed variations directly related to atmospheric conditions. The robust field instrumentation adopted in this study is useful for the accurate monitoring of in-service pipes which may be highly vulnerable to catastrophic failure due to ageing-induced corrosion and severe operational loads.

Commuters' Personal Exposure Assessment and Evaluation of Inhaled Dose to Different Atmospheric Pollutants.

Several studies evaluating exposure to pollutants in microenvironments (MEs) are available in the scientific literature, but studies that evaluate the inhaled doses of pollutants are few in number. Therefore, this study aimed to evaluate the exposure of commuters to different pollutants (i.e., nitrogen dioxide [NO2] and fractionated particulate matter [PM], including ultrafine particles [UFPs]) using miniaturized and portable real-time monitoring instruments in selected MEs; the inhaled doses of these pollutants were estimated for each of these MEs. Measurements were performed along a typical commute, considering different traffic and nontraffic MEs. Experimental data were collected over four working weeks in two different seasons (winter and summer). Different portable and miniaturized instruments were used to evaluate PM and NO2 exposure. Furthermore, physiological parameters were evaluated using a heart rate monitor. The principal results show that higher exposure levels were measured in Underground (for all PM fractions and NO2) and in Car (UFP), while lower levels were measured in Car (PM and NO2) and in Train (UFP). In contrast, higher values of the inhaled cumulative dose were estimated in environments defined as Other, followed by Walking (ht), while lower values were observed in Walking (lt) and in Car.

On the Development of an Instrument for In-Line and Real-Time Monitoring of Blood-pH in Extracorporeal Circulation

The possibility of real-time monitor critical care analytes, such as pH, is recognized to provide relevant information for the diagnosis and treatment of a variety of disorders and would be of considerable support for the management of extracorporeal circulation (ECC). However, despite that blood pH can be measured from a long time by using electrodes or point-of-care instruments, such as blood-gas analyzers, costs, and complications associated with such measurement methods limit their use, thus, blood pH is generally not monitored during routinary ECC. In this article, we propose to exploit the tubing composing the ECC line to realize a low-cost and disposable pH-sensor and to interrogate such fluorescent sensors by using optical radiations. The proposed measuring system avoids complications related to blood sampling and may allow achieving single-patient cost requirements. Preliminary tests performed on a real ECC bloodline demonstrate that the system can operate with blood in ECC. Indeed, a 6-h ECC treatment simulated using bovine blood revealed a deviation with respect to the reference pH-meter typically of about a few thousandths pH and with a maximum of about 0.01 pH.

The Golden Eagle, Peregrine and Solitaire fields, Blocks 14/26a and 20/01, UK North Sea

AbstractThe Golden Eagle Field is located 18 km north of the Buzzard Field in the Moray Firth, and consists of oil accumulations in the Lower Cretaceous Punt and Upper Jurassic Burns Sandstone members. The development area comprises three fields, Golden Eagle, Peregrine and Solitaire, but up to 90% of the oil-in-place and ultimate recovery are in Golden Eagle. The two satellite fields are primarily structural closures, while the Golden Eagle Field reservoirs have a major element of stratigraphic pinchout. Production commenced in October 2014 and approximately 140 MMbbl of recoverable oil is anticipated over its field life from the 19 development wells (14 producers and 5 injectors) that form the initial development phase. Production performance to date has exceeded expectations, aided through the use of completions that provide zonal control of the reservoir units which has successfully supported reservoir management and improved sweep efficiency.A number of significant lessons have been learned during the early stages of the field life from the integration of dynamic data (real-time downhole fibre-optic reservoir monitoring instruments, inter- and intra-well tracers, and well interference tests) and seismic data improvements (post-start-up acquisition of high-density ocean-bottom node seismic and depth-conversion improvements).

Behavioral characteristics of polyhexamethyleneguanidine (PHMG) particles in aqueous solution and air when sprayed into an ultrasonic humidifier

Polyhexamethyleneguanidine (PHMG) is widely used as a disinfectant to prevent microbial contamination in ultrasonic humidifiers in Korea; however, sales have been prohibited by the government after an outbreak of severe lung injury among humidifier disinfectant users. This study was therefore conducted to determine the characteristics of PHMG particles in aqueous solution and to investigate the behavior of airborne particles generated when using PHMG as a humidifier disinfectant. Three types of PHMG were selected (manufactured in Korea, USA, and China), with dynamic light scattering (DLS) used to determine their behavioral characteristics in aqueous solution. To determine the airborne behavioral characteristics, PHMG was diluted to obtain high (62.5–65 ppm) and low (6.25–6.5 ppm) concentrations, and then real-time monitoring instruments were used to measure the effect of using a diffusion dryer and thermodenuder to control moisture in a cleanroom. A polycarbonate filter sample was analyzed by field emission-scanning electron microscope-energy dispersive spectrometry (FE-SEM-EDS) to determine the particle morphology. The DLS intensity results for the three products showed a slightly right-shifted (~100 nm) bimodal distribution relative to the airborne particle size distribution. The size of the airborne PHMG particles increased during the spraying due to aggregation, with the particle size of aggregated particles confirmed by FE-SEM to be approximately 20 nm or more. As the PHMG concentration increased by 10 times, the airborne concentrations measured by the real-time monitoring instrument increased by 2–3 times for nanoparticles, and by 45–85 times for 1–10 μm particles during humidifier operation; however, 99% of the particles generated could be classified as PM1. Without ventilation, even after operating the humidifier, the PHMG particles could be airborne for about 2 h until the background concentration was reached. Therefore, we found that the airborne behavior was affected by PHMG concentration. Products from different manufacturers had no effect on the airborne behavior.

Exposure to Particles and Nitrogen Dioxide Among Workers in the Stockholm Underground Train System

ObjectivesExposure to fine particles in urban air has been associated with a number of negative health effects. High levels of fine particles have been detected at underground stations in big cities. We investigated the exposure conditions in four occupational groups in the Stockholm underground train system to identify high-exposed groups and study variations in exposure.MethodsPM1 and PM2.5 were measured during three full work shifts on 44 underground workers. Fluctuations in exposure were monitored by a real-time particle monitoring instrument, pDR, DataRAM. Qualitative analysis of particle content was performed using inductively coupled plasma mass spectrometry. Nitrogen dioxide was measured using passive monitors.ResultsFor all underground workers, the geometric mean (GM) of PM1 was 18 μg/m3 and of PM2.5 was 37 μg/m3. The particle exposure was highest for cleaners/platform workers, and the GM of PM1 was 31.6 μg/m3 [geometric standard deviation (GSD), 1.6] and of PM2.5 was 76.5 μg/m3 (GSD, 1.3); the particle exposure was lowest for ticket sellers, and the GM of PM1 was 4.9 μg/m3 (GSD, 2.1) and of PM2.5 was 9.3 μg/m3 (GSD, 1.5). The PM1 and PM2.5 levels were five times higher in the underground system than at the street level, and the particles in the underground had high iron content. The train driver's nitrogen dioxide exposure level was 64.1 μg/m3 (GSD, 1.5).ConclusionsCleaners and other platform workers were statistically significantly more exposed to particles than train drivers or ticket sellers. Particle concentrations (PM2.5) in the Stockholm underground system were within the same range as in the New York underground system but were much lower than in several older underground systems around the world.