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This article introduces a novel computational tool for analysing concentrations of particles and gaseous impurities in mechanically ventilated indoor spaces. The computation routine exploits mass balance model assuming well-mixed conditions, and accounts for the most significant means of entry and loss of contaminants. The analysis inputs include time-dependent outdoor concentrations, indoor generation rates, filtration efficiencies and deposition rates. The model was validated using size resolved particle concentrations measured during an experimental campaign. The predicted indoor concentrations were in good correlation with experimental data over wide particle size range. To demonstrate the computational capabilities, indoor concentrations of particles and carbon dioxide were analysed with various combinations of supply air filtration efficiency, ventilation rate, recirculation ratio, air purifiers, and occupancy. Subsequently, a relative sick leave estimate based on time-averaged exposure to total particle mass concentrations was computed. The results emphasised the effectiveness of supply air filtration to limit the exposure to ambient air pollution. Replacing a coarse filter with a high efficiency filter resulted in reduction of an order of magnitude in the relative sick leave estimate. In comparison, increasing recirculation ratio or exploiting air purifiers demonstrated noticeable, but lesser impact.

BACKGROUND Effective design and operation of Intensive Care Unit (ICU) ventilation systems is important to prevent hospital-acquired infections. Air purifiers may contribute to that. AIM In this study we aimed at detecting the number and types of microorganisms present in the air and on the high touch surfaces in the ICU; evaluating the effectiveness of the air purifying device in reducing the microbial load and thus the rate of nosocomial infections in the ICU. METHOD This interventional study was conducted in two similar ICUs between December 2019 and May 2020. Novaerus brand air purifiers were located in the "intervention ICU" for two months. Routine cleaning procedures and HEPA filtered ventilation continued in "control ICU" as well as in the "Intervention ICU". After two months the units were moved to the other ICU for the next two months to reduce any possible bias in the results. Air and surface samples were evaluated. FINDINGS The evaluation of the change in the interventional ICU over time revealed a significantly lower colony concentration in the air and on surfaces on Day 60 compared to Day 1 (pair

In order to further improve the interior air quality and comfort of the vehicle, CFD method is used to simulate the different airflow distribution caused by car-mounted air purifiers at different positions. Combined with the change of formaldehyde concentration field in car, the influence of car-mounted air purifiers on the formaldehyde dilution and removal under the condition of air conditioning air supply is analyzed. The simulation results are verified by actual measurement, and the trend of the simulation results is basically consistent with the measured results. When the car air purifier placed in the middle of the car roof, it can effectively dilute and purify the formaldehyde gas in the car, and reduce the concentration of formaldehyde in the breathing area of the driver and passengers. The adsorption and degradation of formaldehyde by the purifier, together with the dilution of formaldehyde by air supply, can improve the air quality in cars more effectively than using only one of the air purification methods.

В статье выполнен массообменный расчет, определяющий изменение концентрации пылевых частиц заданного фракционного состава в воздухе небольших жилых, административных и производственных помещений. Получены формулы, определяющие значение средней концентрации пылевых частиц в воздухе помещения, при его естественной и искусственной вентиляции и при работе воздухоочистителя. Полученные формулы позволяют с небольшой погрешностью прогнозировать изменение концентрации отдельных фракций пылевых частиц внутри помещения за период времени в несколько часов. Расчет может быть использован при выборе методов и технологий вентиляции и пылеочистки зданий и помещений и дает возможность и подобрать наиболее простые и малозатратные способы вентиляции воздуха, а при очистке воздуха с помощью воздухоочистителя, правильно определить мощность воздухоочистителя и компоновку специализированных фильтров внутри него. Представленные в статье научные результаты могут быть применены в учебном процессе и использованы для проведения дальнейших исследований в соответствующей области., The article performs a mass-exchanging calculation, determining the change in the concentration of dust particles of a given fractional composition in the air of small residential, administrative and industrial premises. The formulas determining the value of the average concentration of dust particles in the air of the premises during its natural and artificial ventilation and during the work of air purifier have been obtained. The obtained formulas allow to predict with a small margin of error the change in the concentration of individual fractions of dust particles inside the premises for a period of a few hours. The calculation can be used when selecting methods and technologies of ventilation and dust treatment of buildings and premises and choosing the simplest and the least expensive methods of air ventilation, and when purifying the air with an air cleaner, to determine correctly the capacity of the air cleaner and the layout of specialized filters inside it. Scientific results presented in the article can be applied in the educational process and used for further research in the relevant field., Международный научно-исследовательский журнал, Выпуск 11 (125) 2022

‘Charaka Samhita’ an ancient text of Ayurveda emphasizes the cleansing of the body through Panchakarma. Today’s generation is out of touch with nature. Poor dietary habits, fast foods, no proper exercise regimen, stress and strain of daily life to compete and survive- these patterns have led to a lot of hormonal changes, and the agents that regulate the body’s mechanism have become poor leading to the spread of toxins throughout the body causing various diseases. As per Ayurveda, these toxins are called “ama”. This foul-smelling, sticky, harmful fluid needs to be completely removed from the body. This is done through Panchkarma, which is advised quarterly, half-yearly, or yearly to get rid of the toxins from the body and also to provide protection from different diseases. This process has twofold benefits – cleansing of the body and also rejuvenation, thus giving a youthful appearance to the body. Panchakarma includes five methods through which the body is detoxified –Procedure of Vamana (induced vomiting), Procedure of Virechana (induced purgation), Basti (enema), Nasya (nasal application), Rakthamokshanana (bloodletting). The three Doshas (vital physiological factors according to Ayurveda) in the human body that is - Vata, Pita, and Kapha are balanced, leading to good physical health and mental balance. Vamanaprocedure means induction of emesis. Through this procedure, the toxins are removed from the body especially through the upper body parts. Vamanaisthe best remedy for Kapha-related diseases. Most of the diseases today are due to improper digestion and metabolism (Agni). The cause is the changing lifestyle full of stress and anxiety. Irregular dietary habits add further to these issues. Diseases need to be uprooted from the base. Therapies like Panchkarma or particular therapy as VamanaKarma for particular Doshas like Kapha can be thought of on a regular basis as a remedy.

Aim and objective The purpose of this study was to evaluate the economic impact and the dental practice changes associated with the coronavirus disease-2019 (COVID-19). Materials and methods This was a cross-sectional survey conducted at the peak of the COVID-19 pandemic (May 2020). The study sample was derived from the Columbia University College of Dental Medicine Alumni network, which included the graduating classes between 1975 and 2015. Active dental practitioners were surveyed regarding changes to their current operations and protective safety measures through a 22 closed-ended questionnaire-based survey. Results The response rate was 17%. Nearly 70.92% of respondents laid off at least one staff member during the COVID-19 pandemic, 51.80% expressed fear of permanent closure, and 79.43% applied for a small business administration loan. There were no significant associations between the amount of time in practice and the need to lay off staff members, the fear of going out of business, or the rates of application for the small business administration loan. Many practitioners bought at least one device geared toward reducing COVID-19 transmission, such as ultraviolet (UV) lights (26.21%), extraoral suctions (37.31%), and high-efficiency particulate air (HEPA) air filters (54.55%). Conclusion At the peak of the pandemic, the majority of dental providers had to reduce staff and seek financial assistance. Concurrently, many of these practices also invested in new safety equipment with the intention of reducing viral transmission. Clinical significance External mouth suctions, commercial air purifiers, and air exchange devices might be useful in the private practice setting. However, financially strained practitioners should recognize that these devices have not currently been proven to be effective against the COVID-19 virus. How to cite this article: Cimilluca JJ, Lee KC, Halepas S et al. COVID-19 Pandemic and its Impact on Dentistry: A Cross-sectional Survey of Practicing Dentists. J Contemp Dent Pract 2021;22(5):473-478.

Neural network models were presented for prediction of indoor concentrations of particulate matters (PMs). Indoor PM concentrations are generally determined by the outdoor concentration, the indoor generation rate, and the air change rate of a building. In this study, indoor PM2.5 and PM10 concentrations were modelled in a single office room installed with a portable air purifier (AP) and a heat recovery ventilator (HRV), using three different neural network models with various input variables. The relative importance of individual input variables indicated that as opposed to PM10, PM2.5 is more affected by outdoor origin than indoor source. This is generally consistent with previous findings explaining that the main source of PM2.5 is outdoor environment, whereas that for PM10 is indoor human activities. The simplified models can be easily applied in practice based on the CO2 concentration measured in a room and the outdoor PM concentration data acquired from public data.

Carbon dioxide is gas produced by industrial pollution and motor vehicle exhaust emissions. The air is declared clean and healthy for human activities if the CO level does not exceed 15 ppm. Industrial pollution or motor vehicle pollution does not only pollute the outdoor air, but it is very likely to pollute the indoor air. For this reason, a system that is able to monitor and control CO levels in the room has been designed so that it is safe for users while doing this activities. The research stage is carried out by making a series of sensors to detect CO gas and then the sensor circuit is connected to the Arduino UNO microcontroller as an interface with a PC. The program used is LabVIEW programming as a neural programming for displaying Virtual Instruments as display media. The output system is an air purifier system that cleans the indoor air when the CO level is more than 15 ppm. Based on the results of trials and analyzes, the response of the sensor system is able to detect changes in CO gas within 7 seconds. The average monitoring of CO levels result when observed 30 times was 11.47 ppm. The air purifier response time is able to restore indoor CO levels to the maximum threshold of 15 ppm in the fastest time of 3 minutes and 22 seconds.

ObjectiveCurrent 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 ...

A wide variety of methods have been applied in indoor air to reduce the microbial load and reduce the transmission rate of acute respiratory diseases to personnel in healthcare sittings. In recent months, with the occurrence of COVID-19 pandemic, the role of portable ventilation systems in reducing the load of virus in indoor air has received much attention. The present study delineates a comprehensive up-to-date overview of the available photocatalysis technologies that have been applied for inactivating and removing airborne viruses. The detection methods for identifying viral particles in air and the main mechanisms involving in virus inactivation during photocatalysis are described and discussed. The photocatalytic processes could effectively decrease the load of viruses in indoor air. However, a constant viral model may not be generalizable to other airborne viruses. In photocatalytic processes, temperature and humidity play a distinct role in the inactivation of viruses through changing photocatalytic rate. The main mechanisms for inactivation of airborne viruses in the photocatalytic processes included chemical oxidation by the reactive oxygen species (ROS), the toxicity of metal ions released from metal-containing photocatalysts, and morphological damage of viruses.

Vape shop employees and electronic cigarette users expose themselves to fine particles (PM2.5, aerodynamic diameter

In Delhi, one of the world's most polluted cities, there is relatively little information on indoor air pollution and how it varies by socioeconomic status (SES). Using indoor air quality monitors (IAQMs), we find that winter levels of household air pollution exceed World Health Organization standards by more than 20 times in both high-and low-SES households. We then evaluate a field experiment that randomly assigned monthlong IAQM user trials across medium-and high-SES households but suffered from significant survey non-response. Among respondents, IAQMs did not affect take-up of subsidized air purifier rentals or other defensive behavior.

In a photocatalytic air purifier system, the catalyst that cleans the air is typically titanium dioxide and it is energized by ultraviolet (UV) light. When UV light shines on the titanium dioxide, electrons (negatively charged particles inside atoms) are released at its surface. The electrons interact with water molecules (H2O) in the air, breaking them up into hydroxyl radicals (OH·), 9which are highly reactive, short-lived, uncharged forms of hydroxide ions (OH-). These small, agile hydroxyl radicals then attack bigger organic (carbon-based like virus) pollutant molecules, breaking apart their chemical bonds and turning them into harmless substances such as carbon dioxide and water. Current investigation uses the above principle to kill living organic germs, bacteria;pathogen, etc. from the cabin air in recirculation mode. A HVAC system has been developed by using a filter impregnated by titanium di-oxide (TiO2) with UV lights to improve and maintain cabin air quality. The developed system has been developed to kill virus, germs, pathogens and bacteria that typically exist in a conditioned space. The designed system can be used for conventional vehicles, EVs, ride sharing and for autonomous vehicles. Tests were conducted at a certified laboratory with MS2, a bacteriophage size of 0.027 microns. MS2 is a proxy for SARS-CoV-2, the virus that causes COVID-19 with a size of 0.125 microns. Effectiveness of the destruction rate was determined for the developed system. Detailed summary will be presented in the paper. © 2021 SAE International. All rights reserved.

CdTe PV cell is one perfect candidate for window application because of its good daylighting performance, low-temperature coefficient and excellent electrical performance under weak light. In addition, thermal catalytic oxidation is an thermal driven air purification technology and the thermal energy can be easily obtained from PV window systems. Therefore, a novel thermal-catalytic CdTe double-layer breathing window was proposed. Firstly, the electrical, thermal and daylighting performances of proposed window were investigated experimentally. Secondly, the removal of formaldehyde was investigated using the verified coupled formaldehyde mass transfer and thermal-catalytic reaction kinetic model. Finally, the evolution of indoor formaldehyde concentration considering formaldehyde release source was calculated. Main results were: (1) The thermal and electrical efficiencies were respectively 0.297 and 0.0715, which were closed to the reported results. Also, the proposed window had better daylighting uniformity compared with conventional window. (2) The total generated clean air was 25.7 m3/(m2•day), with the equivalent formaldehyde degradation efficiency of 0.010 based on purification performances of various air purifiers in market. (3) The comprehensive thermal efficiency was 0.518, with increase of 9.28% considering the contribution from formaldehyde removal. (4) The proposed window could make the indoor concentration approach to standard concentration under most working conditions.

Non-decomposable plastic has been replaced with polylactic acid, which is a biodegradable aliphatic polyester stationary phase, in composite films embedded with a TiO2 photocatalyst for mitigation of indoor air pollution. PLA has superior properties relative to those of other biopolymers, such as a relatively high melting point, crystallinity, and rigidity. This study aimed to incorporate TiO2-anatase into PLA for use as a photocatalyst using the blown film method. Photocatalytic oxidation, an advanced oxidative process, has been recognized as an economical technique providing convenience and efficiency with indoor air treatment. Therefore, the use of new environmentally friendly biodegradable polymers provides an alternative way to address the severe environmental concerns caused by non-decomposable plastics. UV-vis spectrophotometry and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX) were used to observe the dispersibility and mixing capacity of the TiO2-anatase PLA matrix. TiO2 dosages were 5, 10, and 15% (wt/wt), and they were incorporated with a twin-screw extruder. SEM-EDX images demonstrated the homogeneity of TiO2 distribution in the PLA matrix. The energy band gaps of TiO2 in the PLA/TiO2-composite films were between 3.14 and 3.22 eV. The relationship between the photocatalytic oxidation rate and the TiO2 dosage in the PLA/TiO2-composite films was determined. A prototype reactor model is geared toward the development of air purifiers for indoor air conditioning. Rate constants for benzene degradation were obtained using first-order kinetics to find rate constants matching experimental findings. In the PLA/TiO2-composite film, the TiO2-anatase photocatalyst was able to degrade 5 ppm benzene. This work contributes to the use of ecoefficient photocatalytic oxidation.

Ambient fine particulate matter (PM2.5 ), as one of the predominant air pollutants, has achieved effective control in recent years in China. Whether the use of indoor air purifiers is still necessary needs further exploration. A randomized crossover trial was conducted in 54 healthy students in Beijing, China. Participants were randomized assigned to the use of real or sham high-efficiency particulate air filter (HEPA) for a week and changed the status after a washout period. Health measurements of cardiorespiratory biomarkers were performed at the end of each period. Linear mixed-effects models were used to evaluate the association between PM2.5 exposure and cardiorespiratory biomarkers. Compared with sham air purification, average diastolic blood pressure (DBP), fractional exhaled nitric oxide (FeNO), and 8-isoprostane (8-isoPGF2α) levels decreased significantly in the real purification. The effects of indoor air purification on lung function indicators including forced expiratory volume in one second (FEV1 ), peak expiratory flow (PEF), and forced expiratory flow between the 25th and 75th percentile of forced vital capacity (FEF25%-75% ) were also significant. Our findings showed a protective effect of indoor HEPA air purifiers on cardiorespiratory health of young healthy adults reflected by the decreased blood pressure, respiratory inflammation, and systematic oxidative stress and improved lung function.

Indoor air purifiers are increasingly marketed for their health benefits, but their cardiovascular effects remain unclear. We systematically reviewed and meta-analysed randomized controlled trials (RCTs) on the cardiovascular effects of indoor air purification interventions in humans of all ages. We searched Embase, Medline, PubMed, and Web of Science from inception to 22 August 2020. Fourteen cross-over RCTs (18 publications) were included. Systolic blood pressure (SBP) was significantly reduced after intervention (-2.28 [95% CI: -3.92, -0.64] mmHg). There were tendencies of reductions in diastolic blood pressure (-0.35 [-1.52, 0.83] mmHg), pulse pressure (PP) (-0.86 [-2.07, 0.34] mmHg), C-reactive protein (-0.23 [-0.63, 0.18] mg/L), and improvement in reactive hyperaemia index (RHI) (0.10 [-0.04, 0.24]) after indoor air purification, although the effects were not statistically significant. However, when restricting the analyses to RCTs using physical-type purifiers only, significant improvements in PP (-1.56 [-2.98, -0.15] mmHg) and RHI (0.13 [0.01, 0.25]) were observed. This study found potential evidence on the short-term cardiovascular benefits of using indoor air purifiers, especially for SBP, PP and RHI. However, under the Grading of Recommendations Assessment, Development and Evaluation framework, the overall certainty of evidence was very low, which discourage unsubstantiated claims on the cardiovascular benefits of air purifiers. We have also identified several key methodological limitations, including small sample size, short duration of intervention, and the lack of wash-out period. Further RCTs with larger sample size and longer follow-up duration are needed to clarify the cardiovascular benefits of air purification interventions.

Air purifiers should pay much attention to hospital-associated infections, but the role of a single air purifier is limited. The goal of this study was to evaluate the effectiveness of the combined application of the nonequilibrium positive and negative oxygen ion purifier (PNOI) and the high-efficiency particulate air filter (HEPA) on a complex, polluted environment. Two of the better performing purifiers were selected before the study. The efficacy of their use alone and in combination for purification of cigarette particulate matter (PM), Staphylococcus albicans, and influenza virus were then evaluated under a simulated contaminated ward. PNAI and HEPA alone are deficient. However, when they were combined, they achieved 98.44%, 99.75%, and 100% 30 min purification rates for cigarette PM, S. albus, and influenza virus, respectively. The purification of pollution of various particle sizes and positions was optimized and reduced differentials, and a subset of airborne influenza viruses is inactivated. Furthermore, they were superior to ultraviolet disinfection for microbial purification in air. This work demonstrates the strong purification capability of the combined application of these two air purifiers for complex air pollution, which provides a new idea for infection control in medical institutions.

COVID-19 outbreack has reaffirmed the need to maintain ventilation of dental environments properly. This study was carried out to encourage a reflective analysis of the risks of air contamination in Brazilian dental clinics. A narrative review of the literature was carried out on the recommendations of heating, ventilation and air conditioning (HVAC) systems in dental environments, considering the risks of air contamination in Brazilian dental teaching clinics. The literature research was conducted in the PubMed and Google Scholar databases and the main studies that evaluated the climatization systems and portable high efficiency particulate air filtration (HEPA) units in dental environments were included. Furthermore, it were analyzed the guidelines of the Centers for Disease Control and Prevention, the Brazilian National Health Surveillance Agency, the Brazilian Ministry of Health and important institutions of the different countries. After the initial research, a review of the guidelines and articles that assess the use of HEPA units to improve air cleanliness. This analysis was done by different groups of researchers. All documents mentioned that the air quality of the dental offices must follow the protocols in current legislation to ensure the safety of the environs. They reaffirmed that the COVID-19 pandemic makes it imperative that dental environments equipped with air conditioning have mechanical air renewal devices. An alternative for Brazilian dental teaching clinics equipped with mini-splits or window air conditioning could be the installation of exhaust fans and portable HEPA filter units to exchange air and reduce aerosols inside the environments.

The innovation of industrial technology is growing rapidly every day. One of them is The Coway company which produce air purifier and water purifier, whose main vision is to preserve an environment. This company has branches in India and Malaysia. For our research study, we have considered consumer products such as air purifier and water purifiers with marketing communication channel which will affect public’s buying behavior on Conway products. There are various marketing promotion channels to be used by companies and however, the best way to reach the customers are always challenging. This study involves primary data through a survey and involves to identify the best promotion channels that the public in India and Malaysia would vote for. This study helps Coway to promote their products through best strategy so that they can increase the market share through consumers feedback in terms of promotion strategies.

In order to reduce the possible harm caused by air pollution, excellent personal protective materials are attracting more and more attention. Therefore, the research of multifunctional materials that can filter particulate matter (PM) and volatile organic compounds (VOCs) simultaneously is of great significance. In addition, in cold weather, water vapor in the exhaled gas condenses into small droplets inside the respirator causing uncomfortable feeling of dampness. Herein, we prepared several types of cyclodextrin-containing Janus nanofibrous porous membranes by electrospinning, which can efficiently filter PM of different sizes in the air, effectively adsorb VOCs, and orientate moisture from exhaled gas to the outside of the membranes to provide a dry and comfortable environment. These advantageous features, combined with the cheap price and easy availability of component materials and low respiratory resistance, highlight the great potential of these Janus nanofibrous porous membranes in the development of personal wearable air purifiers.

Luftreiniger werden derzeit häufig als mögliches Hilfsmittel zur Minimierung des Infektionsrisikos im Rahmen der COVID-19-Pandemie diskutiert. Dabei taucht oft die Frage auf, ob Luftreiniger grundsätzlich in der Lage sind, Viren oder virenbeladene Tröpfchen abzuscheiden. Ziel dieses Artikels ist es, die wesentlichen Grundlagen der Wirkungsweise von Luftreinigern und Filtern zu beschreiben, Methoden zur Messung der Reinigungswirkung im Größenbereich von Viren und virenbeladenen Tröpfchen aufzuzeigen sowie typische Szenarien zum Betrieb von Luftreinigern in einem mathematischen Modell zu erfassen. Darauf basierend können die Möglichkeiten und Grenzen von Luftreinigern für reale Anwendungsfälle besser eingeschätzt werden.

Für den Lernerfolg der Schüler/-innen und die gesundheitsverträglichen Arbeitsbedingungen der Lehrkräfte im Unterricht existieren hohe akustische Anforderungen, wobei Schall aus Raumlufttechnischen Anlagen (RLT-Anlagen) auf ≤ 35 dB(A) begrenzt ist. Jedoch sind für Unterrichtsräume umfänglich erhebliche bauliche Defizite belegt und insbesondere zu hohe Nachhallzeiten identifiziert worden. Dauerschallerzeugende Mobile Luftreiniger (MLR) würden die vielerorts bereits überschrittenen Belastungsgrenzen zusätzlich verletzen. Je nach MLR-Anzahl und Dauerschallpegel sind die Lehrkräfte gezwungen, lauter zu sprechen (Lombard-Effekt), was zu einer wesentlichen Erhöhung freigesetzter (Virus-)Partikel führt. Um auch während des MLR-Dauerbetriebes mit 54 dB(A) die nach DIN 18041 erforderliche Sprachverständlichkeit an jedem Sitzplatz im Raum sicherzustellen, muss die Lehrkraft ihre Lautstärke erheblich steigern: In Abhängigkeit von der Position im Raum induzieren MLR um die 4,2- bzw. 11,2-fach höheren (Virus-)Lasten, denen alle im Unterricht Anwesenden ausgesetzt sind.

Entgegen den realen Bedingungen basierten die bisherigen Bewertungsverfahren zu mobilen Luftreinigern (MLR) auf dem sofortigen Abbau hoher Partikelkonzentrationen aus homogener Verteilung. Auch wurden wirkungsmindernde Parameter sowie die Bilanzierung zusätzlicher Virus-Lasten im Raum nicht betrachtet, die aufgrund dauerhafter MLR-Lärmpegel und konsekutiv erzwungener lauterer Sprechweise resultieren. Im Simulationsmodell mit einem typischen Unterrichtsraum erwies sich der MLR-Abstand zur (unbekannten) Virus-Quelle als wesentliche Einflussgröße der MLR-Funktion: Es baute sich ein Konzentrationsgradient auf, der bei 8 m Abstand eine Retentionszeit von 10 min bedingte, nach der erstmalig und stark verdünnt Viruspartikel den MLR erreichten. In der Bilanz des MLR-Dauerbetriebes erhöhte sich die Virus-Last im Unterrichtsraum schallbedingt und konnte nur in wenigen Konstellationen (geringer Abstand zur Quelle, hoher Volumenstrom) wieder vollständig entfernt werden bzw. erreichte eine minimale Reduktion im Vergleich zur Belastung ohne MLR-Betrieb.

Für den Lernerfolg der Schüler/-innen und die gesundheitsverträglichen Arbeitsbedingungen der Lehrkräfte im Unterricht existieren hohe akustische Anforderungen, wobei Schall aus Raumlufttechnischen Anlagen (RLT-Anlagen) auf ≤ 35 dB(A) begrenzt ist. Jedoch sind für Unterrichtsräume umfänglich erhebliche bauliche Defizite belegt und insbesondere zu hohe Nachhallzeiten identifiziert worden. Dauerschallerzeugende Mobile Luftreiniger (MLR) würden die vielerorts bereits überschrittenen Belastungsgrenzen zusätzlich verletzen. Je nach MLR-Anzahl und Dauerschallpegel sind die Lehrkräfte gezwungen, lauter zu sprechen (Lombard-Effekt), was zu einer wesentlichen Erhöhung freigesetzter (Virus-)Partikel führt. Um auch während des MLR-Dauerbetriebes mit 54 dB(A) die nach DIN 18041 erforderliche Sprachverständlichkeit an jedem Sitzplatz im Raum sicherzustellen, muss die Lehrkraft ihre Lautstärke erheblich steigern: In Abhängigkeit von der Position im Raum induzieren MLR um die 4,2- bzw. 11,2-fach höheren (Virus-)Lasten, denen alle im Unterricht Anwesenden ausgesetzt sind.