The Removal of Airborne Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and Other Microbial Bioaerosols by Air Filtration on Coronavirus Disease 2019 (COVID-19) Surge Units

Morris, Andrew Conway; Sharrocks, Katherine; Bousfield, Rachel; Kermack, Leanne M.; Maes, Mailis; Higginson, Ellen E.; Forrest, Sally; Pereira-Dias, Joannna; Cormie, Claire; Old, Timothy; Brooks, Sophie; Hamed, Islam; Koenig, Alicia; Turner, Andrew; White, Paul F.; Floto, Andres; Dougan, Gordon; Gkrania‐Klotsas, Effrossyni; Gouliouris, Theodore; Baker, Stephen; Navapurkar, Vilas

doi:10.1093/cid/ciab933

Cited by 64 publications

(58 citation statements)

References 11 publications

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“…This natural experimental study is the first of its kind to comprehensively evaluate both the sequential transport of airborne PM around a medical ward, and to assess the impact of air filtration devices on this. While we did not distinguish between bioaerosols and inert aerosols, the fact that viral particles tend to occur mostly in smaller respiratory aerosols <5 µm diameter [38-40] means that the behaviour of monitored PM signals is likely to have been indicative of any bioaerosols present in the ward air. As such, the study sheds new light on the transport of aerosols around hospital wards that might be helpful in better understanding the dynamics of airborne nosocomial transmission of viruses such as SARS-CoV-2 in clinical settings.…”

Section: Discussionmentioning

confidence: 99%

“…As the majority of airborne virus is thought to be contained in particles of <5 µm [39, 40, 49], the results reported here imply that appropriately sized and situated air filtration devices, supplementing ward ventilation, may have a significant impact on the nosocomial transmission of viral and other microbial infections. Interestingly, Conway-Morris et al [38] observed most viral particles to be in aerosol particles of 1-4 µm diameter, with some in aerosols >4 µm. As well as impacting in the nasopharynx, these smaller aerosols can travel deeper into the lungs to the alveolar level, and there is evidence that this may be associated with more severe disease [12, 13].…”

Section: Discussionmentioning

confidence: 99%

“…as others have found [47, 51], we were not able to determine the proportion of airborne particulates that comprised respiratory aerosols. Previous studies have shown that respiratory viruses are most likely to be recovered from particles <5 µm [38-40, 49], suggesting that they are contained in exhaled bioaerosols that have undergone rapid evaporation [7]. Such aerosols are thought to reduce in size to approximately 30% of their original diameter under normal room conditions [52], which means that exhaled respiratory droplets as large as 100 µm diameter have the potential to transmit SARS-CoV-2 because of evaporation [6, 53].…”

Section: Discussionmentioning

confidence: 99%

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Impact of supplementary air filtration on airborne particulate matter in a UK hospital ward

D¹,

Butler

Peters

et al. 2022

Preprint

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Background During the COVID-19 pandemic, aerosol spread of SARS-CoV-2 has been a major problem in healthcare facilities, resulting in increased use of supplementary HEPA filtration to mitigate transmission. We report here a natural experiment that occurred when an air filtration unit (AFU) on an inpatient ward for older people was accidentally switched off. Aim To assess aerosol transport within the ward and determine whether the AFU reduced particulate matter (PM) levels in the air. Methods Time-series PM, CO2, temperature and humidity data (at 1 minute intervals) was collected from multiple sensors around the ward over two days in August 2021. During this period, the AFU was accidentally switched off for approximately 7 hours, allowing the impact of the intervention on particulates (PM1-PM10) to be assessed using a Mann-Whitney test. Pearson correlation analysis of the PM and CO2 signals was also undertaken to evaluate the movement of airborne particulates around the ward. Findings The AFU greatly reduced PM counts of all sizes throughout the ward space (p<0.001 for all sensors), with PM signals positively correlated with indoor CO2 levels (r = 0.343-0.817; all p<0.001). Aerosol particle counts tended to rise and fall simultaneously throughout the ward space when the AFU was off, with PM signals from multiple locations highly correlated (e.g. r = 0.343-0.868 (all p<0.001) for PM1). Conclusion Aerosols freely migrated between the various sub-compartments of the ward, suggesting that social distancing measures alone cannot prevent nosocomial transmission of SARS-CoV-2. The AFU greatly reduced PM levels throughout the ward space.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Impact of supplementary air filtration on airborne particulate matter in a UK hospital ward

D¹,

Butler

Peters

et al. 2022

Preprint

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“…Similarly, AGPs and contaminated air between rooms or open bay dental chairs could remain a source of contamination [ 34 , 35 ]. There is a growing body of evidence supporting the use of portable air filters [ 36 ] and air cleaners [ 7 ] as mitigating measures to help reduce such risk, however further dental aerosol studies sampling specifically for the virus are required. This study provides further evidence for sources of aerosol generation during common dental procedures, enabling a more holistic approach to risk assessment [ 29 ].…”

Section: Discussionmentioning

confidence: 99%

A clinical observational analysis of aerosol emissions from dental procedures

et al. 2022

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Aerosol generating procedures (AGPs) are defined as any procedure releasing airborne particles <5 μm in size from the respiratory tract. There remains uncertainty about which dental procedures constitute AGPs. We quantified the aerosol number concentration generated during a range of periodontal, oral surgery and orthodontic procedures using an aerodynamic particle sizer, which measures aerosol number concentrations and size distribution across the 0.5–20 μm diameter size range. Measurements were conducted in an environment with a sufficiently low background to detect a patient’s cough, enabling confident identification of aerosol. Phantom head control experiments for each procedure were performed under the same conditions as a comparison. Where aerosol was detected during a patient procedure, we assessed whether the size distribution could be explained by the non-salivary contaminated instrument source in the respective phantom head control procedure using a two-sided unpaired t-test (comparing the mode widths (log(σ)) and peak positions (DP,C)). The aerosol size distribution provided a robust fingerprint of aerosol emission from a source. 41 patients underwent fifteen different dental procedures. For nine procedures, no aerosol was detected above background. Where aerosol was detected, the percentage of procedure time that aerosol was observed above background ranged from 12.7% for ultrasonic scaling, to 42.9% for 3-in-1 air + water syringe. For ultrasonic scaling, 3-in-1 syringe use and surgical drilling, the aerosol size distribution matched the non-salivary contaminated instrument source, with no unexplained aerosol. High and slow speed drilling produced aerosol from patient procedures with different size distributions to those measured from the phantom head controls (mode widths log(σ)) and peaks (DP,C, p< 0.002) and, therefore, may pose a greater risk of salivary contamination. This study provides evidence for sources of aerosol generation during common dental procedures, enabling more informed evaluation of risk and appropriate mitigation strategies.

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“…Alternative measures for protection against SARS-CoV-2 transmission through the air is the use of room air filtration systems. While evidence of transmission reduction with the use of air filters is anecdotal at best, it has been solidified that such systems can remove virus-containing particles from the air [27,28] . Still, it is quite clear, that such systems can only prevent the accumulation of infectious aerosols in closed rooms while direct transmission between persons also via aerosols is still very possible, and could even be enhanced when the airflow generated by the filter is drawing infectious aerosol towards s susceptible person before filtering it.…”

Section: Discussionmentioning

confidence: 99%

Aerosol decontamination and spatial separation using a free-space LED-based UV-C light curtain

Beyerl

Brunn

Rieker

et al. 2021

Preprint

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BackgroundThe SARS-CoV-2 pandemic demonstrated the vulnerability of our societies to aerosol transmitted pathogens. With no less than 260mio known cases and > 5mio deaths, SARS-CoV-2 is a global catastrophe leading to human and economic losses unprecedented in recent history. Thus, effective methods to limit the spread of aerosol transmitted pathogens are needed. Universal masking and curfew laws are effective but no permanent solution.MethodsA mass producible LED light source emitting homogeneous parallel UV-C light was used as a “light-barrier” to block the spread of infectious aerosols. In an aerosol test channel, Gram-negative and Gram-positive bacteria as well as coronavirus were nebulized and inactivation rates were determined.FindingsWith air speeds of 0.1 m s-1 an exposure time of 1 s in the UV-C light is obtained. Reduction in CFU for E. coli was >3log10 and for S. aureus ∼2.8log10. Plug-forming-units of the murine coronavirus (Mouse Hepatitis Virus, MHV) were reduced by about 3log10.InterpretationThe concept of a UV-C light barrier to ward off infectious aerosols if feasible and possible with a light element as described here. Coupled with sensor based activation/deactivation, such a technology could greatly reduce the transmission rates of aerosol transmitted pathogens while not disturbing natural human behaviour. This is an interesting technology allowing a “new normal” in societies after/with SARS-CoV-2.

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The Removal of Airborne Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and Other Microbial Bioaerosols by Air Filtration on Coronavirus Disease 2019 (COVID-19) Surge Units

Cited by 64 publications

References 11 publications

Impact of supplementary air filtration on airborne particulate matter in a UK hospital ward

Impact of supplementary air filtration on airborne particulate matter in a UK hospital ward

A clinical observational analysis of aerosol emissions from dental procedures

Aerosol decontamination and spatial separation using a free-space LED-based UV-C light curtain

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