An unprecedented thunderstorm ground enhancement (TGE) event was recorded on May 23, 2023, at Aragats Mountain, the highest peak in Armenia. This event showcased a maximum flux intensity surpassing 3 ...million particles per minute per square meter for energies above 0.4 MeV. Distinctly, the fluence of the event was measured at approximately ≈700 particles/cm2. The comprehensive instrumentation at the Aragats research station, including a suite of spectrometers and detectors, enabled precise cross-correlation of measurements. The electron flux at energies exceeding 10 MeV was observed at roughly ≈55,000 particles per minute per square meter. Additional measurements, including cloud base heights and corona discharge detections, validated the intensity of the electric field, reaching approximately 2.1 kV/cm at elevations 50–100 m above ground level. Our observations confirm that TGE is a universal and significant atmospheric event, contributing a substantial flux of high-energy electrons to the global electrical circuit. Integrating such TGE phenomena into Earth's numerical models is imperative, considering their impact on aviation and aerospace operation safety.
•A significant impact of air pollution on the gamma-ray spectrum was confirmed.•210Pb and 40K are mostly correlated with the PM concentration in the air.•A purification system for the gamma ...spectrometer chamber was proposed.•The effectiveness of the filtration system has been proven.•For the 46.5 keV ROI of the 210Pb isotope, the background decreased by 71 %.
Gamma-ray spectrometry has wide applications in various fields of science, technology, medicine, and basic research. Despite many advantages of this technique, background quantification constitutes one of the challenges in performing measurements. This study aimed to show the effect of air pollution on gamma spectrometric measurements and provide a low-cost system to improve their quality. To improve the background parameters of the spectrometer, a special system was implemented to ventilate the detector chamber, where the air stream is cleaned using a HEPA (High Efficiency Particulate Air) filter and nitrogen evaporating from the dewar's vessel.. A strong correlation was observed between the concentrations of particulates in the air and the level of count rates in specific areas of the gamma spectrum. For example, the results show a significant effect of reductions in the average number of counts within the 46.5 keV line of the 210Pb isotope, where the background decreased by 71 %.
•In the midst of the current pandemic, outpatient clinics may see an influx of sick patients, of whom some may have COVID-19.•Portable HEPA units can be used to minimize airborne contaminants.•Small ...outpatient exam rooms can benefit from portable HEPA units to make these spaces safer for staff and other patients.
Ambulatory clinics attend to COVID-19 patients, often in spaces with less than ideal ventilation. Testing and treatments can often include aerosol-generating procedures. Portable high efficiency particulate air (HEPA) filtration units have been used to remove airborne contaminants in these areas.
A particle counter was used to evaluate the effectiveness of portable HEPA filtration units when a proxy airborne contaminant (powder) was actuated into the air. The Center for Disease Control and Prevention's (CDC) Airborne Contaminant Removal table served as a basis for initial particle readings at 6 minutes.
Percent decrease was calculated post powder actuation at the 6-minute and 12-minute mark. There was a statistically significant decrease in smaller particles at the 6-minute and 12-minute mark when the HEPA filtration units were used.
As an adjunct infection control intervention, portable HEPA filtration units can make outpatient exam rooms safer for patients and staff by decreasing cumulative airborne particles.
•Interventions are needed to lower household PM2.5 exposures.•Participants were randomized to a control (no air cleaners) or intervention (1–2 air cleaners) group.•Air cleaners lowered indoor PM2.5 ...by 29% (95% CI: 21, 37%) and blood cadmium by 14% (4, 23%).•Air cleaners were most effective in winter, when the PM2.5 geometric mean was reduced from 45 to 29μg/m3.•Air cleaner effectiveness was reduced by >50% after approximately 5months of use.
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Portable HEPA filter air cleaners can reduce indoor fine particulate matter (PM2.5), but their use has not been adequately evaluated in high pollution settings. We assessed air cleaner effectiveness in reducing indoor residential PM2.5 and second hand smoke (SHS) exposures among non-smoking pregnant women in Ulaanbaatar, Mongolia.
We randomized 540 participants to an intervention group receiving 1 or 2 HEPA filter air cleaners or a control group receiving no air cleaners. We followed 259 intervention and 253 control participants to the end of pregnancy. We measured one-week indoor residential PM2.5 concentrations in early (~11weeks gestation) and late (~31weeks gestation) pregnancy and collected outdoor PM2.5 data from centrally-located government monitors. We assessed blood cadmium in late pregnancy. Hair nicotine was quantified in a subset (n=125) to evaluate blood cadmium as a biomarker of SHS exposure. We evaluated air cleaner effectiveness using mixed effects and multiple linear regression models and used stratified models and interaction terms to evaluate potential modifiers of effectiveness.
The overall geometric mean (GM) one-week outdoor PM2.5 concentration was 47.9μg/m3 (95% CI: 44.6, 51.6μg/m3), with highest concentrations in winter (118.0μg/m3; 110.4, 126.2μg/m3). One-week indoor and outdoor PM2.5 concentrations were correlated (r=0.69). Indoor PM2.5 concentrations were 29% (21, 37%) lower in intervention versus control apartments, with GMs of 17.3μg/m3 (15.8, 18.8μg/m3) and 24.5μg/m3 (22.2, 27.0μg/m3), respectively. Air cleaner effectiveness was greater when air cleaners were first deployed (40%; 31, 48%) than after approximately five months of use (15%; 0, 27%). Blood cadmium concentrations were 14% (4, 23%) lower among intervention participants, likely due to reduced SHS exposure.
Portable HEPA filter air cleaners can lower indoor PM2.5 concentrations and SHS exposures in highly polluted settings.
Aerosol-generating procedures in the office represent a major concern for health care-associated infection of patients and health care providers by SARS-CoV-2, the causative agent for coronavirus ...disease 2019 (COVID-19). Although the Centers for Disease Control and Prevention has not yet provided any recommendations for the use of portable air purifiers, air purifiers with high-efficiency particulate air (HEPA) filters have been discussed as an adjunctive means for decontamination of SARS-CoV-2 aerosols in health care settings. This commentary discusses HEPA filter mechanisms of action, decontamination time based on efficiency and flow rate, theoretical application to SARS-CoV-2, and limitations. HEPA filter functionality and prior guidance from the Centers for Disease Control and Prevention for SARS-CoV-1 suggest theoretical efficacy for HEPA filters to decontaminate airborne SARS-CoV-2, although direct studies for SARS-CoV-2 have not been performed. Any portable HEPA purifier utilization for SARS-CoV-2 should be considered an adjunctive infection control measure and undertaken with knowledge of HEPA filter functionality and limitations in mind.
•Establishment of empirical equation for pressure drop across multi-V cabin filter.•Measurements of pressure drop across various multi-V cabin filters for verification of the empirical ...equation.•Development of two optimized design procedures for multi-V HEPA filters and comparison with actual parameters.
With the wide use of multi-V filters in aircraft cabins, it is necessary to establish a pressure drop prediction and optimization model for multi-V HEPA cabin filters. Based on approximate solution of the Navier-Stokes equation and with the aid of CFD simulations, we developed an empirical equation for the overall pressure drop across a multi-V HEPA cabin filter. The measured pressure drop across the filter was used to verify the accuracy of the empirical equation. The equation was then used to develop two optimized design procedures for multi-V HEPA cabin filters with low pressure drop and high filtration efficiency. The structural parameters of the filters obtained by the two design procedures were consistent and very close to the actual parameters. Compared with CFD, this empirical equation is easier to use and involves only a short calculation time. The empirical equation and optimized design procedures are useful for filter design.
Current epidemiologic predictions of COVID-19 suggest that SARS-CoV-2 mitigation strategies must be implemented long-term. In-office aerosol-generating procedures pose a risk to staff and patients ...while necessitating examination room shutdown to allow aerosol decontamination by indwelling ventilation. This review summarizes the current state of knowledge on portable high-efficiency particulate air (HEPA) purifiers' effectiveness in eliminating airborne SARS-CoV-2 from indoor environments.
Medline, Embase, Cochrane Databases, and the World Health Organization's COVID-19 Global Literature on Coronavirus Disease.
Data sources were systematically searched for original English-language published studies indexed up to January 14, 2021 per the following search strategy: ("HEPA" OR "High-efficiency" OR "High-efficiency particulate air" OR "Efficiency particulate" OR "Purifier" OR "Filter" OR "Cleaner" OR "Filtration") AND ("COVID" OR "COVID-19" OR "SARS-CoV-2" OR "Coronavirus"). Additional relevant studies were identified by searching the reference lists of included articles.
Eleven published studies have evaluated the effectiveness of portable HEPA purifiers in eliminating airborne SARS-CoV-2 with relevantly sized surrogate particles. Ten studies evaluated aerosols and submicron particles similar in size to SARS-CoV-2 virions. In all studies, portable HEPA purifiers were able to significantly reduce airborne SARS-CoV-2-surrogate particles. The addition of portable HEPA purifiers augmented other decontamination strategies such as ventilation.
Experimental studies provide evidence for portable HEPA purifiers' potential to eliminate airborne SARS-CoV-2 and augment primary decontamination strategies such as ventilation. Based on filtration rates, additional air exchanges provided by portable HEPA purifiers may be calculated and room shutdown times potentially reduced after aerosol-generating procedures.
High efficiency air filtration has been suggested to reduce airborne transmission of ‘infectious’ aerosols. In this study the ‘air cleaning’ effect as well as the effect on sound and air velocity ...(draught risk) of a mobile High-Efficiency Particulate Air (HEPA) filter system was tested for different settings and positions in the Experience room of the SenseLab. From both the noise assessments by a panel of subjects and sound monitoring it was concluded that the mobile HEPA filter system causes an unacceptable background sound level in the tested classroom setting (Experience room). With respect to the air velocity measurements and draught rating calculations, it was concluded that both depend on the position and the setting of the HEPA filter system as well as on the position and height of the measurements. For the removal of aerosols simulated by air-filled soap bubbles in front of the subject, the mobile HEPA filter system performed better as compared to the ‘No ventilation’ regime, for all settings and both positions, and for some settings, even better than all the tested mixing ventilation regimes. The use of a mobile HEPA filter system seems a good additional measure when only natural ventilation options are available. Future research should focus on rooms of different sizes or shapes, as this may also play a role in the filter's performance, noise and draught effects.
•A mobile HEPA filter system is a good additional measure to natural ventilation.•The mobile system can result in unacceptable noise levels and draught effects.•The HEPA filter's cleaning performance depends on setting and position in a room.
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