A novel VOC breath tracer method to evaluate indoor respiratory exposures in the near- and far-fields; implications for the spread of respiratory viruses.

BACKGROUND: Several studies suggest that far-field transmission (>6 ft) explains a significant number of COVID-19 superspreading outbreaks. OBJECTIVE: Therefore, quantifying the ratio of near- and far-field exposure to emissions from a source is key to better understanding human-to-human airborne infectious disease transmission and associated risks. METHODS: In this study, we used an environmentally-controlled chamber to measure volatile organic compounds (VOCs) released from a healthy participant who consumed breath mints, which contained unique tracer compounds. Tracer measurements were made at 0.76 m (2.5 ft), 1.52 m (5 ft), 2.28 m (7.5 ft) from the participant, as well as in the exhaust plenum of the chamber. RESULTS: We observed that 0.76 m (2.5 ft) trials had ~36-44% higher concentrations than other distances during the first 20 minutes of experiments, highlighting the importance of the near-field exposure relative to the far-field before virus-laden respiratory aerosol plumes are continuously mixed into the far-field. However, for the conditions studied, the concentrations of human-sourced tracers after 20 minutes and approaching the end of the 60-minute trials at 0.76 m, 1.52 m, and 2.28 m were only ~18%, ~11%, and ~7.5% higher than volume-averaged concentrations, respectively. SIGNIFICANCE: This study suggests that for rooms with similar airflow parameters disease transmission risk is dominated by near-field exposures for shorter event durations (e.g., initial 20-25-minutes of event) whereas far-field exposures are critical throughout the entire event and are increasingly more important for longer event durations. IMPACT STATEMENT: We offer a novel methodology for studying the fate and transport of airborne bioaerosols in indoor spaces using VOCs as unique proxies for bioaerosols. We provide evidence that real-time measurement of VOCs can be applied in settings with human subjects to estimate the concentration of bioaerosol at different distances from the emitter. We also improve upon the conventional assumption that a well-mixed room exhibits instantaneous and perfect mixing by addressing spatial distances and mixing over time. We quantitatively assessed the exposure levels to breath tracers at alternate distances and provided more insights into the changes on "near-field to far-field" ratios over time. This method can be used in future to estimate the benefits of alternate environmental conditions and occupant behaviors.

Recent progress in online detection methods of bioaerosols

The aerosol transmission of coronavirus disease in 2019, along with the spread of other respiratory diseases, caused significant loss of life and property;it impressed upon us the importance of real-time bioaerosol detection. The complexity, diversity, and large spatiotemporal variability of bioaerosols and their external/internal mixing with abiotic components pose challenges for effective online bioaerosol monitoring. Traditional methods focus on directly capturing bioaerosols before subsequent time-consuming laboratory analysis such as culture-based methods, preventing the high-resolution time-based characteristics necessary for an online approach. Through a comprehensive literature assessment, this review highlights and discusses the most commonly used real-time bioaerosol monitoring techniques and the associated commercially available monitors. Methods applied in online bioaerosol monitoring, including adenosine triphosphate bioluminescence, laser/light-induced fluorescence spectroscopy, Raman spectroscopy, and bioaerosol mass spectrometry are summarized. The working principles, characteristics, sensitivities, and efficiencies of these real-time detection methods are compared to understand their responses to known particle types and to contrast their differences. Approaches developed to analyze the substantial data sets obtained by these instruments and to overcome the limitations of current real-time bioaerosol monitoring technologies are also introduced. Finally, an outlook is proposed for future instrumentation indicating a need for highly revolutionized bioaerosol detection technologies.

Insights on the methodology for indoor microbial aerosol studies

Covid-19 has highlighted the need for reliable methods for airborne microbe control. Different microbes are suitable for different purposes, and the microbes are sensitive to collection methods used. We identified three safe-to-use microbes suitable for airborne microbial studies: MS2-bacteriophage virus, Staphylococcus simulans and Bacillus atrophaeus bacterial spores. We found that the sensitive microbes (MS2 and S. simulans) survive better, when collected directly in a liquid media. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Estimating aerosol particle removal in indoor air by ion-enhanced deposition

Small air ions have the ability to charge airborne particles, thereby increasing their accumulation on surfaces. Indoor air purification by applying ionization uses electrostatic particle deposition. Respiratory pathogens, including viruses and respiratory droplets carrying viruses or other pathogens, represent bioaerosols, whose particle size distributions contain increasingly larger proportion of fine and ultrafine particles, as the evaporation process proceeds. We have generated two model aerosols: the nebulized NaCl solution, resembling human saliva, and the cigarette smoke, having relatively low water content. We have conducted real life experiments of such surrogate aerosol particle deposition without ionization, using bipolar ionization, as well as using unipolar negative air ions. Particle number concentrations have been measured in the 10 nm–10 μm particle size range. The calculated deposition rates and aerosol particle half-life times were correlated with bioaerosol pathogens based on the core pathogen sizes. Bipolar ionizers emitting equal concentrations of positive and negative ions had low impact to the particle concentration decrease. Intense negative air ionization resulted in pronounced deposition rate increases, particularly in the particle size range of viruses including the SARS-CoV-2. The impact of negative air ionization was most pronounced in the same size range where the deposition rates without ionization were the lowest. Therefore, the results are very promising from the standpoint of air purification and bioaerosol pathogen removal, bearing in mind that the effect of ions will be most pronounced if the unipolar ion rich air stream is directed towards the breathing zone.

Monitoring of indoor bioaerosol for the detection of SARS-CoV-2 in different hospital settings.

Background: Spore Trap is an environmental detection technology, already used in the field of allergology to monitor the presence and composition of potentially inspirable airborne micronic bioparticulate. This device is potentially suitable for environmental monitoring of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in hospital, as well as in other high-risk closed environments. The aim of the present study is to investigate the accuracy of the Spore Trap system in detecting SARS-CoV-2 in indoor bioaerosol of hospital rooms. Methods: The Spore Trap was placed in hospital rooms hosting patients with documented SARS-CoV-2 infection (n = 36) or, as a negative control, in rooms where patients with documented negativity to a Real-Time Polymerase Chain Reaction molecular test for SARS-CoV-2 were admitted (n = 10). The monitoring of the bioaerosol was carried on for 24 h. Collected samples were analyzed by real-time polymerase chain reaction. Results: The estimated sensitivity of the Spore Trap device for detecting SARS-CoV-2 in an indoor environment is 69.4% (95% C.I. 54.3-84.4%), with a specificity of 100%. Conclusion: The Spore Trap technology is effective in detecting airborne SARS-CoV-2 virus with excellent specificity and high sensitivity, when compared to previous reports. The SARS-CoV-2 pandemic scenario has suggested that indoor air quality control will be a priority in future public health management and will certainly need to include an environmental bio-investigation protocol.

Reactive Air Disinfection Technologies: Principles and Applications in Bioaerosol Removal

As COVID-19 and other infectious diseases continue to spread globally, removing airborne pathogens from confined spaces such as buildings, transportation carriers, and stations is becoming increasingly crucial to curbing transmission and reducing human infection rates. Bioaerosols can act as vectors or media that could store and transport air pollutants and pathogens. To mitigate the adverse effects of bioaerosols and effectively control epidemics, this work reviews the current state-of-the-art air purification processes and technologies available on the market or demonstrated in laboratory and industrial settings, including ozone oxidation, UV disinfection, and photocatalysis. These reactive air purification processes can be used in conjunction with adsorption or filtration-based systems to enhance disinfection besides the physical capture of particulates or the removal of volatile organic compounds (VOCs). This review aims to provide a concise yet comprehensive overview of various reactive air purification technologies. Their principles, applications, and limitations are briefly discussed to provide insight and guidelines for further development of new air purification processes to address emerging airborne contaminant issues. © 2023 American Chemical Society.

Markers of Chemical and Microbiological Contamination of the Air in the Sport Centers.

This study aimed to assess the markers of chemical and microbiological contamination of the air at sport centers (e.g., the fitness center in Poland) including the determination of particulate matter, CO2, formaldehyde (DustTrak™ DRX Aerosol Monitor; Multi-functional Air Quality Detector), volatile organic compound (VOC) concentration (headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry), the number of microorganisms in the air (culture methods), and microbial biodiversity (high-throughput sequencing on the Illumina platform). Additionally the number of microorganisms and the presence of SARS-CoV-2 (PCR) on the surfaces was determined. Total particle concentration varied between 0.0445 mg m-3 and 0.0841 mg m-3 with the dominance (99.65-99.99%) of the PM2.5 fraction. The CO2 concentration ranged from 800 ppm to 2198 ppm, while the formaldehyde concentration was from 0.005 mg/m3 to 0.049 mg m-3. A total of 84 VOCs were identified in the air collected from the gym. Phenol, D-limonene, toluene, and 2-ethyl-1-hexanol dominated in the air at the tested facilities. The average daily number of bacteria was 7.17 × 102 CFU m-3-1.68 × 103 CFU m-3, while the number of fungi was 3.03 × 103 CFU m-3-7.34 × 103 CFU m-3. In total, 422 genera of bacteria and 408 genera of fungi representing 21 and 11 phyla, respectively, were detected in the gym. The most abundant bacteria and fungi (>1%) that belonged to the second and third groups of health hazards were: Escherichia-Shigella, Corynebacterium, Bacillus, Staphylococcus, Cladosporium, Aspergillus, and Penicillium. In addition, other species that may be allergenic (Epicoccum) or infectious (Acinetobacter, Sphingomonas, Sporobolomyces) were present in the air. Moreover, the SARS-CoV-2 virus was detected on surfaces in the gym. The monitoring proposal for the assessment of the air quality at a sport center includes the following markers: total particle concentration with the PM2.5 fraction, CO2 concentration, VOCs (phenol, toluene, and 2-ethyl-1-hexanol), and the number of bacteria and fungi.

The role of HFNC

Acute respiratory infection due to 2019 novel coronavirus (2019-nCoV) is now known as novel coronavirus-infected pneumonia (NCIP). In the hospitalized NCIP patients, the time from disease onset to shortness of breath was median 8 days and to development of ARDS was median 10.5 days. Most of the patients received oxygen therapy. HFNC has many physiological advantages compared with other standard oxygen therapies, such as anatomical dead space washout, more constant fraction of inspired oxygen (FiO2), and supplement of adequate humidification, and is one of the oxygen therapies for critically ill patients. In this care setting, the use of HFNC with its indications and benefits, precautions for aerosols, and the combined use with the prone position are the subject of active scientific interest especially for older patients. © Springer Nature Switzerland AG 2020.

Effect of coronavirus (Covid-19) pandemic on biological air pollutants: a case study of Valiasr hospital in Zanjan (2019-2020)

Background and Objective: Bioaerosols as small particles enter the body by inhalation and lead to respiratory diseases based on type, concentration, and exposure time. In sensitive workplaces such as medical centers, it is necessary to pay attention to the type and population of these pollutants and the possibility of nosocomial infections. In the present study, the population and type of bioaerosols (bacteria and fungi) in the air of different hospital wards under normal conditions, visiting hours, and Covid-19 pandemic was evaluated. Materials and Methods: Air sampling was carried out in different wards and ambient air of Valiasr Hospital of Zanjan during September 2019 (morning and visiting hours) and October 2020 (Corona pandemic) using an air sampling pump (Flite 3-SKC Ltd) with a flow of 14.1 L/min and then cultured in Sabaroud dextrose agar and nutrient agar. Results: The results showed that air pollution in wards such as infectious diseases and clinics in both periods was more than other wards. The microbial density during visiting hours (before the coronavirus outbreak) was almost 30% higher than normal conditions. In October 2020, due to the coronavirus outbreak and reduced traffic, microbial air pollution in the hospital decreased. In both periods of study, the frequency of gram-positive bacteria, especially Staphylococcus species (49%) was higher than other bacteria and among fungal species the frequency of Aspergillus (47%) was higher than others. Conclusion: This study showed that traffic restrictions caused by the coronavirus pandemic reduce microbial density in hospital space and this achievement can be used in the future with the aim of improving air quality and controlling nosocomial infections. © 2022 Iranian Association of Environmental Health, and Tehran University of Medical Sciences.

Room-Based Assessment of Mobile Air Cleaning Devices Using a Bioaerosol Challenge.

Introduction: The widespread transmission of the SARS-CoV-2 virus has increased scientific and societal interest in air cleaning technologies, and their potential to mitigate the airborne spread of microorganisms. Here we evaluate room scale use of five mobile air cleaning devices. Methods: A selection of air cleaners, containing high efficiency filtration, was tested using an airborne bacteriophage challenge. Assessments of bioaerosol removal efficacy were undertaken using a decay measurement approach over 3 h, with air cleaner performance compared with bioaerosol decay rate without an air cleaner in the sealed test room. Evidence of chemical by-product emission was also checked, as were total particle counts. Results: Bioaerosol reduction, exceeding natural decay, was observed for all air cleaners. Reductions ranged between devices from <2-log per m3 room air for the least effective, to a >5-log reduction for the most efficacious systems. One system generated detectable ozone within the sealed test room, but ozone was undetectable when the system was run in a normally ventilated room. Total particulate air removal trends aligned with measured airborne bacteriophage decline. Discussion: Air cleaner performance differed, and this could relate to individual air cleaner flow specifications as well as test room conditions, such as air mixing during testing. However, measurable reductions in bioaerosols, beyond natural airborne decay rate, were observed. Conclusion: Under the described test conditions, air cleaners containing high efficiency filtration significantly reduced bioaerosol levels. The best performing air cleaners could be investigated further with improved assay sensitivity, to enable measurement of lower residual levels of bioaerosols.

Performance evaluation of an electrostatic precipitator with a copper plate using an aerosolized SARS-CoV-2 surrogate (bacteriophage phi 6).

The global spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has reminded us of the importance of developing technologies to reduce and control bioaerosols in built environments. For bioaerosol control, the interaction between researchers and biomaterials is essential, and considering the characteristics of target pathogens is strongly required. Herein, we used enveloped viral aerosols, bacteriophage phi 6, for evaluating the performance of an electrostatic precipitator (ESP) with a copper-collecting plate (Cu-plate). In particular, bacteriophage phi 6 is an accessible enveloped virus that can be operated in biosafety level (BSL)-1 as a promising surrogate for SARS-CoV-2 with structural and morphological similarities. ESP with Cu-plate showed >91% of particle removal efficiency for viral aerosols at 77 cm/s of airflow face velocity. Moreover, the Cu-plate presented a potent antiviral performance of 5.4-relative log reduction within <15 min of contact. We believe that the evaluation of ESP performance using an aerosolized enveloped virus and plaque assay is invaluable. Our results provide essential information for the development of bioaerosol control technologies that will lead the post-corona era.

Three Experimental Common High-Risk Procedures: Emission Characteristics Identification and Source Intensity Estimation in Biosafety Laboratory.

Biosafety laboratory is an important place to study high-risk microbes. In biosafety laboratories, with the outbreak of infectious diseases such as COVID-19, experimental activities have become increasingly frequent, and the risk of exposure to bioaerosols has increased. To explore the exposure risk of biosafety laboratories, the intensity and emission characteristics of laboratory risk factors were investigated. In this study, high-risk microbe samples were substituted with Serratia marcescens as the model bacteria. The resulting concentration and particle size segregation of the bioaerosol produced by three experimental procedures (spill, injection, and sample drop) were monitored, and the emission sources' intensity were quantitatively analyzed. The results showed that the aerosol concentration produced by injection and sample drop was 103 CFU/m3, and that by sample spill was 102 CFU/m3. The particle size of bioaerosol is mainly segregated in the range of 3.3-4.7 µm. There are significant differences in the influence of risk factors on source intensity. The intensity of sample spill, injection, and sample drop source is 3.6 CFU/s, 78.2 CFU/s, and 664 CFU/s. This study could provide suggestions for risk assessment of experimental operation procedures and experimental personnel protection.

Development of a portable bioaerosol capture device for influenza virus detection

Many bacteria and viruses are spreading in the air in the living environment, and high concentrations of viruses entering the human body will cause harm. This research is committed to developing a virus collector, which is used to collect influenza and coronavirus in the air. In our system, the intake fan can beget negative pressure into the water circulation channel and bring the virus into it, and then the sensor chip will obtain the electrical signal. In this study, we successfully used methylene blue to simulate viruses in the air. The result of this experiment showed that the distance between the air virus collector and the atomizer was 30 cm in height, 60 cm & 90 cm in length. The capture efficiency was respectively 1.1% and 0.8%. Also, we use lateral flow immunochromatographic assay to detect the collected samples of Influenza H1N1 Hemagglutinin Protein, and the actual limit of detection is 16.97 ng/ml. In addition, the experiments also proved that the water circulation device in this study could accumulate the methylene blue samples onto the sensor. In the future, it can be used with the sensor chip as a virus detection platform which can collect and monitor viruses simultaneously. By using this device, people can be warned and take the necessary precautions to reduce the chance of the transmission of viruses.

Carbohydrate vitrification in aerosolized saliva is associated with the humidity-dependent infectious potential of airborne coronavirus.

An accepted murine analogue for the environmental behavior of human SARS coronaviruses was aerosolized in microdroplets of its culture media and saliva to observe the decay of its airborne infectious potential under relative humidity (RH) conditions relevant to conditioned indoor air. Contained in a dark, 10 m3 chamber maintained at 22°C, murine hepatitis virus (MHV) was entrained in artificial saliva particles that were aerosolized in size distributions that mimic SARS-CoV-2 virus expelled from infected humans' respiration. As judged by quantitative PCR, more than 95% of the airborne MHV aerosolized was recovered from microdroplets with mean aerodynamic diameters between 0.56 and 5.6 µm. As judged by its half-life, calculated from the median tissue culture infectious dose (TCID50), saliva was protective of airborne murine coronavirus through a RH range recommended for conditioned indoor air (60% < RH < 40%; average half-life = 60 minutes). However, its average half-life doubled to 120 minutes when RH was maintained at 25%. Saliva microaerosol was dominated by carbohydrates, which presented hallmarks of vitrification without efflorescence at low RH. These results suggest that dehydrating carbohydrates can affect the infectious potential coronaviruses exhibit while airborne, significantly extending their persistence under the drier humidity conditions encountered indoors.

Bioaerosol dispersion and environmental risk simulation: Method and a case study for a biopharmaceutical plant of Gansu province, China.

Pathogenic bacteria pose a great threat to global public health from environmental and public health perspectives, especially regarding the impact of the COVID-19 pandemic worldwide. As a result, the increased risk of pathogenic bioaerosol exposure imposes a considerable health burden and raises specific concerns about the layout and location of vaccine manufacturers. This study proposed a grid computing method based on the CALPUFF modelling system and population-based environmental risks to reduce bioaerosol-related potential risks. We previously used the CALPUFF model to quantify the diffusion level, the spatial distribution of emissions, and potential environmental risks of bioaerosol leakage in Gansu province's Zhongmu Lanzhou biopharmaceutical plant from July 24, 2019, to August 20, 2019. By combining it with publicly available test data, the credibility was confirmed. Based on our previous research, the CALPUFF model application combined with the environmental population-based environmental risks in two scenarios: the layout and site selection, was explored by using the leakage accident of Zhongmu Lanzhou biopharmaceutical plant of Gansu province as a case study. Our results showed that the site selection method of scenario 2 coupled with the buffer area was more reasonable than scenario 1, and the final layout site selection point of scenario 2 was grid 157 as the optimal layout point. The simulation results demonstrated agreement with the actual survey. Our findings could assist global bioaerosol manufacturers in developing appropriate layout and site selection strategies to reduce bioaerosol-related potential environmental risks.

Factors to consider in the performance evaluation of an air purifier using an airborne virus (Phi-X174) in a large chamber

Devices for the filtration and sterilization of indoor spaces have been widely used owing to the outbreak of the novel coronavirus disease 2019 (COVID-19). There is a need for a standard method to test the effectiveness of such devices. In this study, we aimed to identify important factors that must be considered while evaluating the efficiency of air purifiers in a large chamber. Investigation of the distribution characteristics of airborne viruses in the large chamber show that they were evenly distributed. Natural (gravitational) reduction of airborne viruses in the large chamber was also investigated. We found that the airborne-virus removal efficiency of an air purifier in a large chamber should be evaluated after 40 min for better accuracy because the concentration of airborne viruses rapidly decreased within the first 40 min and the settling velocity reduced after 40 min. In addition, the minimum standard deviation of airborne-virus removal efficiency of air purifier was 1.9% with a natural reduction time of 40 min. Moreover, the sampling efficiencies of three types of samplers were compared. The impactor showed the highest sampling efficiency (4.8 x 104-5.1 x 104 PFU/m3-min) and a small standard deviation (0.9 x 104 PFU/m3-min). Copyright © The Author(s) 2023.

Estimating the restraint of SARS-CoV-2 spread using a conventional medical air-cleaning device: Based on an experiment in a typical dental clinical setting.

OBJECTIVES: Droplets or aerosols loaded with SARS-CoV-2 can be released during breathing, coughing, or sneezing from COVID-19-infected persons. To investigate whether the most commonly applied air-cleaning device in dental clinics, the oral spray suction machine (OSSM), can provide protection to healthcare providers working in clinics against exposure to bioaerosols during dental treatment. METHOD: In this study, we measured and characterized the temporal and spatial variations in bioaerosol concentration and deposition with and without the use of the OSSM using an experimental design in a dental clinic setting. Serratia marcescens (a bacterium) and ΦX174 phage (a virus) were used as tracers. The air sampling points were sampled using an Anderson six-stage sampler, and the surface-deposition sampling points were sampled using the natural sedimentation method. The Computational Fluid Dynamics method was adopted to simulate and visualize the effect of the OSSM on the concentration spatial distribution. RESULTS: During dental treatment, the peak exposure concentration increased by up to 2-3 orders of magnitude (PFU/m3) for healthcare workers. Meanwhile, OSSM could lower the mean bioaerosol exposure concentration from 58.84 PFU/m3 to 4.10 PFU/m3 for a healthcare worker, thereby inhibiting droplet and airborne transmission. In terms of deposition, OSSM significantly reduced the bioaerosol surface concentration from 28.1 PFU/m3 to 2.5 PFU/m3 for a surface, effectively preventing fomite transmission. CONCLUSION: The use of OSSM showed the potential to restraint the spread of bioaerosols in clinical settings. Our study demonstrates that OSSM use in dental clinics can reduce the exposure concentrations of bioaerosols for healthcare workers during dental treatment and is beneficial for minimizing the risk of infectious diseases such as COVID-19.

Conceptual design for an ultra-sensitive bioaerosol detection system

The detection of aerosols in general and bioaerosols more specific has gained an increased importance in multiple fields. While environmental scientists are increasingly interested in the impacts of aerosols onto climatic effects, researchers in the security sector are looking for ways to remotely detect dangerous substances from safe distances. Additionally, due to the corona pandemic, the detection of bioaerosols has gained significant relevance in sectors like public health, transportation, and aviation. As a result, more accurate, i.e. sensitive and specific, measurement equipment is needed. Here we present the design concept for a new sensor system designed to measure thin bioaerosol clouds. For the detection air samples are excited with laser light to generate a signal based on laser induced fluorescence. The fluorescence is collected in an integration sphere to optimize signal. Inside the integration sphere multiple sensors are placed, each combined with a filter to exclude all signals not belonging to a certain, agent specific wavelength interval. Through the intelligent combination of spectral intervals, a specific characteristic of the studied air sample is measured. Based on the measured characteristic a classification is performed to determine the category of the sample. Development aims at testing indoor air quality in real time. © 2022 SPIE.

In vitro model for investigating aerosol dispersion in a simulated COVID-19 patient during high-flow nasal cannula treatment.

The use of high-flow nasal cannula in the treatment of COVID-19 infected patients has proven to be a valuable treatment option to improve oxygenation. Early in the pandemic, there were concerns for the degree of risk of disease transmission to health care workers utilizing these treatments that are considered aerosol generating procedures. This study developed an in vitro model to examine the release of simulated patient-derived bioaerosol with and without high-flow nasal cannula at gas flow rates of 30 and 50 L/min. Aerosol dispersion was evaluated at 30 and 90 cm distances. Reduction of transmission risk was assessed using a surgical facemask on the manikin. Results indicated that the use of a facemask facilitated a 94-95% reduction in exhaled aerosol concentration at 30 cm and 22-60% reduction for 90 cm distance across both gas flow rates. This bench study confirms that this in vitro model can be used as a tool to assess the risk of disease transmission during aerosol generating procedures in a simulated patient and to test factors to mitigate the risk.

Development of a high-speed bioaerosol elimination system for treatment of indoor air.

We developed a high-speed filterless airflow multistage photocatalytic elbow aerosol removal system for the treatment of bioaerosols such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Human-generated bioaerosols that diffuse into indoor spaces are 1-10 µm in size, and their selective and rapid treatment can reduce the risk of SARS-CoV-2 infection. A high-speed airflow is necessary to treat large volumes of indoor air over a short period. The proposed system can be used to eliminate viruses in aerosols by forcibly depositing aerosols in a high-speed airflow onto a photocatalyst placed inside the system through inertial force and turbulent diffusion. Because the main component of the deposited bioaerosol is water, it evaporates after colliding with the photocatalyst, and the nonvolatile virus remains on the photocatalytic channel wall. The residual virus on the photocatalytic channel wall is mineralized via photocatalytic oxidation with UVA-LED irradiation in the channel. When this system was operated in a 4.5 m3 aerosol chamber, over 99.8% aerosols in the size range of 1-10 µm were removed within 15 min. The system continued delivering such performance with the continuous introduction of aerosols. Because this system exhibits excellent aerosol removal ability at a flow velocity of 5 m/s or higher, it is more suitable than other reactive air purification systems for treating large-volume spaces.