Synergistic Enhancement of Filtering Efficiency and Antibacterial Performance of a Nanofiber Air Filter Decorated with Electropolarized Lithium-Doped ZnO Nanorods.

According to clinical case reports, bacterial co-infection with COVID-19 can significantly increase mortality, with Staphylococcus aureus (S. aureus) being one of the most common pathogens causing complications such as pneumonia. Thus, during the pandemic, research on imparting air filters with antibacterial properties was actively initiated, and several antibacterial agents were investigated. However, air filters with inorganic nanostructures on organic nanofibers (NFs) have not been investigated extensively. This study aimed to demonstrate the efficiency of electropolarized poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) NFs decorated with Li-doped ZnO nanorods (NRs) to improve the filtering ability and antibacterial activity of the ultrathin air filter. The surfactant was loaded onto the ZnO─known for its biocompatibility and low toxicity─nanoparticles (NPs) and transferred to the outer surface of the NFs, where Li-doped ZnO NRs were grown. The Li-doped ZnO NR-decorated NF effectively enhanced the physical filtration efficiency and antibacterial properties. Additionally, by exploiting the ferroelectric properties of Li-doped ZnO NRs and PVDF-TrFE NFs, the filter was electropolarized to increase its Coulombic interaction with PMs and S. aureus. As a result, the filter exhibited a 90% PM1.0 removal efficiency and a 99.5% sterilization rate against S. aureus. The method proposed in this study provides an effective route for simultaneously improving the air filter performance and antibacterial activity.

Efficient, Breathable, and Compostable Multilayer Air Filter Material Prepared from Plant-Derived Biopolymers.

State-of-art face masks and respirators are fabricated as single-use devices using microfibrous polypropylene fabrics, which are challenging to be collected and recycled at a community scale. Compostable face masks and respirators can offer a viable alternative to reducing their environmental impact. In this work, we have developed a compostable air filter produced by electrospinning a plant-derived protein, zein, on a craft paper-based substrate. The electrospun material is tailored to be humidity tolerant and mechanically durable by crosslinking zein with citric acid. The electrospun material demonstrated a high particle filtration efficiency (PFE) of 91.15% and a high pressure drop (PD) of 191.2 Pa using an aerosol particle diameter of 75 ± 2 nm at a face velocity of 10 cm/s. We deployed a pleated structure to reduce the PD or improve the breathability of the electrospun material without compromising the PFE over short- and long-duration tests. Over a 1 h salt loading test, the PD of a single-layer pleated filter increased from 28.9 to 39.1 Pa, while that of the flat sample increased from 169.3 to 327 Pa. The stacking of pleated layers enhanced the PFE while retaining a low PD; a two-layer stack with a pleat width of 5 mm offers a PFE of 95.4 ± 0.34% and a low PD of 75.2 ± 6.1 Pa.

Interventions for improving indoor and outdoor air quality in and around schools

Students spend nearly one third of their typical day in the school environment, where they may be exposed to harmful air pollutants. A consolidated knowledge base of interventions to reduce this exposure is required for making informed decisions on their implementation and wider uptake. We attempt to fill this knowledge gap by synthesising the existing scientific literature on different school-based air pollution exposure interventions, their efficiency, suitability, and limitations. We assessed technological (air purifiers, HVAC - Heating Ventilation and Air Conditioning etc.), behavioural, physical barriers, structural, school-commute and policy and regulatory interventions. Studies suggest that the removal efficiency of air purifiers for PM2.5, PM10, PM1 and BC can be up to 57 %, 34 %, 70 % and 58 %, respectively, depending on the air purification technology compared with control levels in classroom. The HVAC system combined with high efficiency filters has BC, PM10 and PM2.5 removal efficiency up to 97 %, 34 % and 30 %, respectively. Citizen science campaigns are effective in reducing the indoor air pollutants' exposure up to 94 %. The concentration of PM10, NO2, O3, BC and PNC can be reduced by up to 60 %, 59 %, 16 %, 63 % and 77 %, respectively as compared to control conditions, by installing green infrastructure (GI) as a physical barrier. School commute interventions can reduce NO2 concentration by up to 23 %. The in-cabin concentration reduction of up to 77 % for PM2.5, 43 % for PNC, 89 % for BC, 74 % for PM10 and 75 % for NO2, along with 94 % reduction in tailpipe emission of total particles, can be achieved using clean fuels and retrofits. No stand-alone method is found as the absolute solution for controlling pollutants exposure, their combined application can be effective in most of the scenarios. More research is needed on assessing combined interventions, and their operational synchronisation for getting the optimum results.Copyright © 2022 The Authors

Electrospun Cyclodextrin/Poly(L-lactic acid) Nanofibers for Efficient Air Filter: Their PM and VOC Removal Efficiency and Triboelectric Outputs.

In this work, PLLA and CD/PLLA nanofibers were fabricated using electrospinning and utilized as a particulate matter (PM) and volatile organic compounds (VOCs) filter. The electrospun PLLA and CD/PLLA were characterized with various techniques, including SEM, BET, FTIR, XRD, XPS, WCA, DSC, tensile strength testing, PM and VOCs removal efficiency, and triboelectric performance. The results demonstrated that the best air filter was 2.5 wt%CD/PLLA, which performed the highest filtration efficiencies of 96.84 ± 1.51% and 99.38 ± 0.43% for capturing PM2.5 and PM10, respectively. Its PM2.5 removal efficiency was 16% higher than that of pure PLLA, which were contributed by their higher surface area and porosity. These 2.5 wt%CD/PLLA nanofibers also exhibited the highest and the fastest VOC entrapment. For triboelectric outputs, the 2.5 wt%CD/PLLA-based triboelectric nanogenerator provided the highest electrical outputs as 245 V and 84.70 µA. These give rise to a three-fold enhancement of electrical outputs. These results indicated that the 2.5 wt%CD/PLLA can improve surface charge density that could capture more PM via electrostatic interaction under surrounding vibration. Therefore, this study suggested that 2.5 wt%CD/PLLA is a good candidate for a multifunction nanofibrous air filter that offers efficient PM and VOC removal.

Preparation, characterization, and air filtration property of electrospun bimodal fibrous membrane based on low conductivity blended polymers solution

One–step preparation of electrospun bimodal fibrous membrane based on single nozzle is the key to the efficient fabrication of high–performance air filter. However, the preparation mechanism of electrospun bimodal fibers at low conductivity solution system is not clear, and there is a lack of evaluation methods for the quality of bimodal nanofibers, which limits the applicability of single nozzle electrospinning and the preparation efficiency of electrospun bimodal fibers. Here, three electrospinning processes at low conductivity solution systems of polyamide–6 (PA6), PA6 blended PVP (PA6/PVP), and PA6 blended polyethylene oxide (PA6/PEO) were studied according to the rheological properties and the fluid electrics (i.e., zeta potential), and the quality of the prepared bimodal fibrous membrane was creatively evaluated by R value. Inhomogeneous phase separations of the electrospinning jet along the direction parallel (x–axis) or perpendicular (y–axis) to the electric field were responsible for the formation of bimodal fibers. In addition, for the same solution system, the R value had a positive correlation with the air filtration performance. This work will greatly enhance the applicability of one–step single nozzle electrospinning for the preparation of bimodal nanofibers, improve the preparation efficiency, and promote the development of high–performance air filter. © 2022 Elsevier Ltd

Particle Pollution, increase in Allergy and Asthma cases and application of Nanotechnology

Rationale: The aerosolized solid, liquid, mix-phased particles are the Particulate Matter or PM having serious health impacts. In the recent years with the unprecedented situation of COVID-19 pandemic, it became a necessity that the scientific world comes forward with an objective of developing more equipment for air purification with novel technology to combat airborne pathogen, aeroallergen and viruses. We have applied AFLPCO Nanotechnology to build equipment and mask. Methods: We built a fiberglass chamber to evaluate the capacity of the AFL-Mask to prevent entry of particulate matters and pathogens. To evaluate the air in the chamber, we used a LightHouse Handheld Particle Counter to sample airborne particles. We have recorded the particle concentrations at time-intervals to determine the percentage of particles entering the other chamber with the mask placed in the junction dividing the chamber. Results: This mask involves a 4-stage filtration system designed to combat all forms of airborne pathogens including bacteria, viruses, mold spores and harmful VOCs. We found that the AFL-Mask was efficient in preventing any particulate matter including PM2.5, PM10, bacterial and fungal spores and VOCs. Conclusions: The AFL-Mask and AFLPCO air purifiers built for long-term use to improve the inhaled air quality. The ergonomic design with padded lining and straps and improved filtration technology made the AFL-Mask a superior mask that provides a continuous airflow to prevent suffocation, troubled breathing and fluctuating blood pressure, especially pertaining to patients with cardiovascular or pulmonary issues. AFLPCO airpurifers were efficient in improving IAQ.

COVID-19 Risk Management in Dental Offices: A Review Article

BACKGROUND: As all the dental staff, including nurses and practitioners, are exposed to various routes of contamination due to the novel COVID-19 virus, which is still unknown to the scientific world, developing strategies to reduce the risk of transmission and decontaminate surfaces in a dental office would be of high importance. Although there is still insufficient data on managing this virus in dental offices, several studies have suggested protocols for improving care. AIM: This study aimed to review present investigations and reach a conclusion on what we know and need to know to combat this virus. MATERIALS AND METHODS: In this review, Scopus, PubMed, and MEDLINE databases were searched using the keywords "COVID-19,” "SARS-CoV-2,” "Medical Disinfectants,” "Personal Protective Equipment's,” and "Surface Decontamination.” Articles were reviewed, and finally, relevant articles published during 2000–2022 were included in the final paper. RESULTS: The present research concluded that using a combination of the face shield and N95 masks protected the eyes, nose, and mouth. To have more efficient protection, water-resistant long-sleeved gowns and gloves were highly suggested. To overcome aerosols, high-performance air filters and ultraviolet were found quite effective. Allowing the patient to use antiseptic mouthwash before starting the treatment could reduce oral microorganisms and the following airborne contamination. CONCLUSION: This review has gathered all available data regarding dentistry and COVID-19 in order to conclude what has been achieved yet in the prevention of this virus through dental offices;however, more investigations are needed to have a definitive protocol against the virus.

Helmet CPAP bundle: A narrative review of practical aspects and nursing interventions to improve patient's comfort.

BACKGROUND: The application of Continuous Positive Airway Pressure (CPAP) with a helmet is increasing around the world, both inside and outside of the intensive care unit. Current published literature focus's on indications, contraindications and efficiency of Helmet CPAP in differing clinical scenarios. Few reports, summarising the available knowledge concerning technical characteristics and nursing interventions to improve patient's comfort, are available. AIM: To identify the crucial technical aspects in managing patients undergoing Helmet-CPAP, and what nursing interventions may increase comfort. METHODS: A narrative literature review of primary research published 2002 onwards. The search strategy comprised an electronic search of three bibliographic databases (Pubmed, Embase, CINAHL). RESULTS: Twenty-three studies met the inclusion criteria and were included in the review. Research primarily originated from Italy. Nine key themes emerged from the review: gas flow management, noise reduction, impact of gas flow and HME filters on delivered FiO2, filtration of exhaled gas / environmental protection, PEEP monitoring, airway pressure monitoring, active humidification of gas flow, helmet fixation and tips to implement awake prone position during Helmet-CPAP. CONCLUSIONS: A Helmet-CPAP check-list has been made of nine key interventions based on the available evidence regarding system set up, monitoring and management. Implementation of this check-list may help nurses and physicians to increase the comfort of patients treated with Helmet CPAP and enhance their compliance with long-term treatment.

Short-Term Use Biocontainment Bubbles: Innovative Source Containment of Potentially Infectious SARS-CoV-2 Aerosols.

Introduction: This article will review the processes utilized to develop simple effective containment engineering controls. Short-Term Use Biocontainment Bubbles-Yale (STUBB-Ys), as Yale refers to them, were designed, built, tested, and implemented to protect members of the Yale University community from exposure to SARS-CoV-2 aerosols. STUBB-Ys were designed and created in conjunction with end users, constructed by Environmental Health and Safety (EHS) or partner groups, and tested onsite after installation to verify effective operation and containment. Methods: A wide variety of devices in different settings were developed and installed. STUBB-Ys were used at COVID-19 indoor test centers, laboratories, and clinics. The devices were pursued to create infection prevention measures where existing processes could not be utilized or were inadequate. Each STUBB-Y was tested with a C-Breeze Condensed Moisture Airflow Visualizer to generate smoke and a Fluke 985 Particle Counter, which gives the particle counts from 0.3 to 10 µm to measure particle escape visually and quantitatively. Airflow rates were also tested where applicable with a TSI VelociCalc 9525 Air Velocity Meter. Results: Students and faculty were able to safely continue vital research or clinical study in the targeted areas with the addition of these simple containment devices to confine aerosols. Conclusion: From a biorisk management point of view, EHS was able to confine aerosols at their potential source using simple designs and equipment and adhering to the hierarchy of controls. This article demonstrates how a straightforward design process can be used to enhance worker protection during a pandemic.

Aero-manufacture of nanobulges for an in-place anticoronaviral on air filters.

The interest in removing contagious viruses from indoor air using ventilation and filtration systems is increasing rapidly because people spend most of the day indoors. The development of an effective platform to regenerate the antiviral function of air filters during use and safe abrogation of used filters containing infectious viruses is a challenging task, because an on-demand safe-by-design manufacture system is essential for in-place antiviral coatings, but it has been rarely investigated. With these considerations, an electrically operable dispenser was prepared for decorating continuous ultrafine Fe-Zn, Fe-Ag, or Fe-Cu particles (<5 nm) onto SiO2 nanobeads (ca. 130 nm) to form nanobulges (i.e., nanoroughness for engaging coronavirus spikes) in the aerosol state for 3 min direct deposition on the air filter surfaces. The resulting nanobulges were exposed to human coronaviruses (HCoV; surrogates of SARS-CoV-2) to assess antiviral function. The results were compared with similar-sized individual Zn, Ag, and Cu particles. The nanobulges exhibited comparable antiviral activity to Zn, Ag, and Cu particles while retaining biosafety in both in vitro and in vivo models because of the significantly smaller metallic fractions. This suggests that the bimetallic bulge structures generate reactive oxygen species and Fenton-mediated hydroxyl radicals for inactivating HCoV.

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.

Performance Study of Composite Air Filters Using Heterogeneous Fibers

Recently, the worldwide demand for disposable masks has increased due to COVID-19 infections and severe air pollution. Personal masks should reduce breathe resistance while maintaining filtering performance. In this study, a solution blowing process is used to produce composite nanofiber filters to co-spin two polymers at once. The manufacture process of the various fiber diameter filter was designed, and the filtration performance and differential pressure of the prepared filter was investigated. Poly vinylidene fluoride-hexafluoropropylene (PVDF-HFP) and Polylactic acid (PLA) fibers were chosen to be entangled together in a layer with a diameter of 1.05 mu m and 0.33 mu m. Composite nanofilters showed up to 87% filtration efficiency and 32 Pa differential pressure.

Antibacterial Capability of Air Filter Fiber Materials Treated with Triclosan against Indoor Environmental Microbes

Antibacterial filtration materials have been used effectively to control biological pollutants and purify indoor air. This study aimed to assess the antibacterial capability of three fiber filter materials treated with triclosan: glass fiber (GF), non-woven fabric (NF) and chemical fiber (CF). Triclosan was loaded onto the filtration materials by the impregnation method. The triclosan-treated filter materials exhibited antibacterial zones obviously: the average antibacterial bands against E. coli were 11.8 mm (GF), 13.3 mm (NF) and 10.5 mm (CF);against S. albus, they were 25.5 mm (GF), 21.0 mm (NF) and 23.5 mm (CF). The percent reductions of bacteria for the antibacterial air fiber materials treated with triclosan against E. coli were 71.4% (CF) and 62.6% (GF), while the percent reductions against S. albus were 61.3% (NF) and 84.6% (CF). These findings could help to reduce the transmission and threat of epidemic and purify the environment through the use of environmentally friendly antibacterial filter fibers.

Effects of Different Test Media on the Test Results of Automobile Cabin Air Filter

Automobile cabin air filters have been ever-increasingly detected since the outburst of COVID-19. However, the dust sources adopted are varied due to the numerous standards. In this study, the effects of different dust sources on the test results of filtration efficiency were explored, and the causes for the different test media used in different standards were analyzed. The study results provide a reference for further improving the performance of vehicle cabin air filters. © 2021 SPIE

Polymersomes as virus-surrogate particles for evaluating the performance of air filter materials.

The development of antivirus air filter materials has attracted considerable interests due to the pandemic of coronavirus disease 2019 (COVID-19). Filtration efficiency (FE) of these materials against virus is critical in the assessment of their use in disease prevention. Due to the high cost and biosafety laboratory required for conducting research using actual virus samples, surrogates for virus are commonly used in the filtration test. Here, we explore the employment of polymersomes (polymeric vesicles) as a new type of surrogate. The polymersomes are hollow shell nanoparticles with amphiphilic bilayer membranes, which can be fabricated in nanosized, and possess similar size and structural features to virus. The performance of commercial KN95 mask and surgical mask with micro-sized fibers, and electrospun polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) nanofibers were chosen to be evaluated. The filtration tests against fluorescent-labeled virus-surrogate particles (VSPs), i.e. polymersomes, allowed the determination of the FE of the multilayered filter materials in a layer-specific manner. The results suggested the importance of hydrophobicity in designing the nanofibrous filter materials. The employment of VSPs in filtration performance evaluation allows a cost-effective way to estimate the FE against virus, providing guidance on future development of air filter materials.

Melamine sponge-based copper-organic framework (Cu-CPP) as a multi-functional filter for air purifiers.

COVID-19 has drawn great attention on the necessity for establishing pathogen-free indoor air. This paper offers an insight into the potential application of a multi-purpose filter to remove fine particulates and disinfect pathogens using melamine sponge with a copper-organic framework. In-situ growth dip coating method was applied to coat Cu-based coordination polymer particle (Cu-CPP) on melamine sponge (MS). The integration of Cu-CPPs with high crystallinity and highly active surface area (1,318.1 m2/g) enabled Cu-CPP/MS to have an excellent capture rate (99.66%) and an instant disinfection rate of 99.54% for Escherichia coli. Electrostatic attraction seemed to play a crucial role in capturing negative-charged pathogens effectively by positive charges on Cu-CPP arising from unbalanced copper ions in Cu-CPP. Disinfection of pathogens was mainly attributed to catalytically active Cu2+ sites. Organic ligand played an important role in bridging and maintaining Cu2+ ions within the framework. This study highlights the design of a new capture-and-disinfection (CDS) air filter system for pathogens using Cu-CPP/MS. It can be applied as a substitute for conventional high-efficiency particulate air (HEPA) filters. Electronic Supplementary Material: Supplementary material is available for this article at 10.1007/s11814-021-1000-4 and is accessible for authorized users.

Combating with poor Indoor air quality to improve work environment at IndianOil

Introduction: Indoor air quality have a great impact on physical and psychological health of employees working in buildings. IndianOil Institute of Petroleum Management (IiPM), located in National Capital Region of Delhi(NCR) is a premiere institute consisting of multiple training halls & auditoriums. In view of COVID-19 pandemic, modifications were carried out in air handling unit system at IiPM. Materials and methods: A detailed study of air movements, intake and return path was carried to find out measures to ensure adequate air exchanges. Additional air inlets with Dual PM10 filters were fixed on all air intake paths to reduce the pollutant level in air entering the building. The air handling unit at the institute was also fitted with special grade air filter for bringing down the PM2.5 level below 60. Special grade filters filtered the pollutants and reduced the pollutant level of air. An online air image sensor was installed to measure the quality of ambient air after filtration. Stand-alone air cleaner/filter units were also installed in training halls, lobbies and waiting areas. Result: Following modifications there was improvement in air quality by 90%. This resulted in building confidence level and provided a stress-free safe environment for employees working at the institute. Employees working at IiPM confirmed reduction in eye irritation, headaches and fatigue due to air pollution. Discussion: Installation of air filters inside the building helps in improving air quality which in turn prevents common health issues at workplace. This has prompted us to provide similar solutions in other office buildings in NC

VENTILATED N95 RESPIRATORS REDUCE CO2 REBREATHING AND HAVE BETTER ACCEPTABILITY

Background and Aims: N95 respirator mask are worn when performing aerosol generating procedures in patient with COVID-19 infection. N95 masks are known to increase work of breathing and providers frequently develop headache, tiredness, and lack of concentration that is known to impact complex tasks. Our aims were to test if positive and negative pressure ventilation mitigate CO2 rebreathing while maintaining the N95 mask integrity and to assess if this is associated with increased acceptance of ventilated mask. Methods: As shown in (Figure 1), negative pressure ventilation was achieved by using dual magnets to attach a suction (180 mm Hg) to the standard N95 respirator mask (Aura 1870+, 3M, St. Paul, MN). The positive pressure ventilation was achieved by creating a sealed opening in the standard N95 respirator mask connected via a tubing to a rechargeable and portable H13 PM2.5 high efficiency air-purifier at airflow rate of 1.2 cfm at a low 17DB sound (Aurora, Cypress, Tx). In mask, CO2 rebreathing levels were measured using E-sCAi0 (GE Healthcare, Helsinki, Finland). Five volunteers scored the acceptance based on established R-COMFI score. Data presented as mean±SEM. Results: Significantly lower mean CO2 levels were noted when negative pressure (16±6 mm Hg) or positive pressure (24±6 mm Hg) mask ventilation measures were used compared to non-ventilated (38±2 mm Hg, p<0.05) 95 respirator mask (Figure 2). Overall mask acceptance using R-COMFI score was significantly better for both negative (5.36±0.5) and positive (9.36±0.4) pressure ventilated masks compared to non-ventilated (9.36±1, p<0.05) N95 respirator mask. The favorable R-COMFI scores for negative pressure ventilation N95 mask were influenced by decreased discomfort but the favorable positive pressure ventilation N95 mask R-COMFI scores were influenced by better wearing experience and function. Both negative and positive pressure ventilated mass passed fit testing without any compromise to its ability to prevent aerosol exposure. Conclusion: Modification of N95 respirator mask by negative or positive pressure ventilation decreases rebreathing of high concentration of CO2 trapped in the mask. Ventilated masks are effective to prevent aerosol exposure and have better acceptance. Developing novel ventilated mask will be useful strategy during the pandemic as well as in the future at workplace with potential biologic and non-biologic exposures. (Image Presented) (Image Presented) (Image Presented)

Airborne particle control methods in dental clinics: A low-cost technique of assessment

Background and Objectives: The COVID-19 pandemic has highlighted the risk of airborne transmission of infections in health-care facilities such as dental clinics. In this experimental study, methods to control airborne particles in a simulated dental clinic setting were measured and compared using a low cost and convenient technique. Materials and Methods: Particles representing inhalable airborne particles were generated using smoke from incense sticks and their concentration measured by handheld particle sensors whereas using different engineering controls for the particle removal in dental clinic equivalent settings. Measurements were made at short (<3 ft) and intermediate (between 3 and 6 ft) distance from the source. The particle filtration through surgical masks and N95 masks was also studied. Results: Natural ventilation, by keeping windows open, can reduce intermediate range particles (removal of 4.7% of ambient particles/min). However, in closed facilities without natural ventilation, particle removal by air purifier combined with overhead fan or with high volume evacuators was found most suitable for intermediate range particles (25.9%/min) and for short range particles (27.6%/min), respectively. N95 masks were found to filter out 99.5% of the generated PM 2.5 particles. Conclusions: Potentially inhalable airborne particles can persist in the air of a dental clinic. The use of N95 masks and environmental controls is essential for the dental team's safety. The choice of an engineering control is governed by multiple factors explained in the study. Smoke particles generated by incense sticks and measurement by handheld particle sensors are low-cost methods to estimate the effectiveness of airborne particle controls.

Indoor air purifiers in the effort to reduce the spread of Coronavirus Disease 2019 (COVID-19): The advantage of circumferential outflow diffusers

Aerosol particles containing virions or the ribonucleic acid (RNA) of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) can be airborne. It has been recently hypothesized that the outflow from air purifiers with a directional outlet could entrain SARSCoV-2-containing particles. Because only the case of a directional outflow was examined, here we investigate an indoor air purifier with a circumferential outflow diffuser instead of a directional outflow, the other typical design. We measured the airflow velocity at two different angles to the surface of the circumferential outflow diffuser and two motor-fan speeds. We visualized in scattered light the deflection of a vertical mist spray cone from a sneeze-simulating nebulizer parallel to the side of the air purifier. We found a significant difference in airflow velocities for different angles to the circumferential outflow diffuser: 0.01 m/s – 0.02 m/s for 0° vs. 0.01 m/s – 0.65 m/s for 45° at 1 m distance. We observed no significant deflection of the sneeze-simulating spray cone at the minimum blower speed and a 5 cm deflection at the maximum speed under the experimental conditions. The deflection of the sneeze-simulating spray mist particles by the tested indoor air purifier with the circumferential outflow, under the experimental conditions, is low relative to the recommended safer distances between people in indoor spaces aimed at reducing the spread of COVID-19. Equipping indoor air purifiers with circumferential outflow diffusers has a considerably lower potential to spread infectious aerosols in indoor spaces compared to devices with unidirectional outflow. © 2021 Proceedings of the Air and Waste Management Association's Annual Conference and Exhibition, AWMA. All rights reserved.