scholarly journals Predictive and retrospective modelling of airborne infection risk using monitored carbon dioxide

2021 ◽  
pp. 1420326X2110435
Author(s):  
Henry C. Burridge ◽  
Shiwei Fan ◽  
Roderic L. Jones ◽  
Catherine J. Noakes ◽  
P. F. Linden
Keyword(s):  
Carbon Dioxide ◽  
Absolute Risk ◽  
Infection Risk ◽  
Expected Number ◽  
Indoor Space ◽  
Airborne Infection ◽  
Secondary Infections ◽  
School Classroom ◽  
Open Plan ◽  
Ventilation Rates

The risk of long range, herein ‘airborne', infection needs to be better understood and is especially urgent during the COVID-19 pandemic. We present a method to determine the relative risk of airborne transmission that can be readily deployed with either modelled or monitored CO2 data and occupancy levels within an indoor space. For spaces regularly, or consistently, occupied by the same group of people, e.g. an open-plan office or a school classroom, we establish protocols to assess the absolute risk of airborne infection of this regular attendance at work or school. We present a methodology to easily calculate the expected number of secondary infections arising from a regular attendee becoming infectious and remaining pre/asymptomatic within these spaces. We demonstrate our model by calculating risks for both a modelled open-plan office and by using monitored data recorded within a small naturally ventilated office. In addition, by inferring ventilation rates from monitored CO2, we show that estimates of airborne infection can be accurately reconstructed, thereby offering scope for more informed retrospective modelling should outbreaks occur in spaces where CO2 is monitored. Well-ventilated spaces appear unlikely to contribute significantly to airborne infection. However, even moderate changes to the conditions within the office, or new variants of the disease, typically result in more troubling predictions.

scholarly journals Low Cost tool for finding ventilation rates for Airborne Infection Control in the Built Environment

2020 ◽  
Author(s):  
Raja Singh
Keyword(s):  
Carbon Dioxide ◽  
Natural Ventilation ◽  
Low Cost ◽  
Ambient Air ◽  
Disease Spread ◽  
Indoor Space ◽  
Airborne Infection ◽  
New Apparatus ◽  
The Cost ◽  
Ventilation Rates

Dilution Ventilation is an accepted way of providing Natural Ventilation for reduction of Disease spread in Indoor Spaces. It is most relevant in low resource settings where the cost of advanced technologies may be a barrier. Studies have been performed in India to find a correlation between Ventilation of spaces and its role in the prevention of Tuberculosis, which is a major airborne disease with high incidence levels in India. These studies lack the measurement of the air changes in the room which is an important criterion to find out the disease spread by transmission models. This paper presents a new apparatus prepared to measure Air changes in an indoor space using Carbon Dioxide as a biomarker which acts as a surrogate for the ventilation in the space. The apparatus prepared uses a pre-existing carbon dioxide meter but adds value to it by creating a tamper-proof, vandal-resistant and a poke-resistant system. It also includes a built-in air suction and withdrawal system so that the sensor can be supplied with the ambient air in the room so that it can accurately give the carbon dioxide measurements. The study enhances the methods of investigation for Indoor Air Quality studies.

scholarly journals Seasonal variation in airborne infection risk in schools due to changes in ventilation inferred from monitored carbon dioxide

Indoor Air ◽  
2021 ◽  
Author(s):  
Carolanne V. M. Vouriot ◽  
Henry C. Burridge ◽  
Catherine J. Noakes ◽  
Paul F. Linden
Keyword(s):  
Carbon Dioxide ◽  
Seasonal Variation ◽  
Infection Risk ◽  
Airborne Infection

scholarly journals The Vaccination Threshold for SARS-CoV-2 Depends on the Indoor Setting and Room Ventilation

2021 ◽  
Author(s):  
Alex Mikszewski ◽  
Luca Stabile ◽  
Giorgio Buonanno ◽  
Lidia Morawska
Keyword(s):  
Vaccination Rate ◽  
Indoor Environments ◽  
Expected Number ◽  
Vaccination Rates ◽  
Susceptibility To Infection ◽  
Airborne Infection ◽  
Community Transmission ◽  
Second Year ◽  
Ventilation Rates ◽  
Theoretical Minimum

Background: Effective vaccines are now available for SARS-CoV-2 in the second year of the COVID-19 pandemic, but there remains significant uncertainty surrounding the necessary vaccination rate to safely lift occupancy controls in public buildings and return to pre-pandemic norms. The aim of this paper is to estimate setting-specific vaccination thresholds for SARS-CoV-2 to prevent sustained community transmission using classical principles of airborne contagion modeling. We calculated the airborne infection risk in three settings, a classroom, prison cell block, and restaurant, at typical ventilation rates, and then the expected number of infections resulting from this risk at varying levels of occupant susceptibility to infection. Results: We estimate the vaccination threshold for control of SARS-CoV-2 to range from a low of 40% for a mechanically ventilation classroom to a high of 85% for a naturally ventilated restaurant. Conclusions: If vaccination rates are limited to a theoretical minimum of approximately two-thirds of the population, enhanced ventilation above minimum standards for acceptable air quality is needed to reduce the frequency and severity of SARS-CoV-2 superspreading events in high-risk indoor environments.

scholarly journals The vaccination threshold for SARS-CoV-2 depends on the indoor setting and room ventilation

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
A. Mikszewski ◽  
L. Stabile ◽  
G. Buonanno ◽  
L. Morawska
Keyword(s):  
Vaccination Rate ◽  
Indoor Environments ◽  
Wild Type ◽  
Expected Number ◽  
Vaccination Rates ◽  
Airborne Infection ◽  
Minimum Standards ◽  
Community Transmission ◽  
Ventilation Rates ◽  
Theoretical Minimum

Abstract Background Effective vaccines are now available for SARS-CoV-2 in the 2nd year of the COVID-19 pandemic, but there remains significant uncertainty surrounding the necessary vaccination rate to safely lift occupancy controls in public buildings and return to pre-pandemic norms. The aim of this paper is to estimate setting-specific vaccination thresholds for SARS-CoV-2 to prevent sustained community transmission using classical principles of airborne contagion modeling. We calculated the airborne infection risk in three settings, a classroom, prison cell block, and restaurant, at typical ventilation rates, and then the expected number of infections resulting from this risk at varying percentages of occupant immunity. Results We estimate the setting-specific immunity threshold for control of wild-type SARS-CoV-2 to range from a low of 40% for a mechanically ventilation classroom to a high of 85% for a naturally ventilated restaurant. Conclusions If vaccination rates are limited to a theoretical minimum of approximately two-thirds of the population, enhanced ventilation above minimum standards for acceptable air quality is needed to reduce the frequency and severity of SARS-CoV-2 superspreading events in high-risk indoor environments.

scholarly journals Numerical investigation of airborne infection in naturally ventilated hospital wards with central-corridor type

2016 ◽  
Vol 27 (1) ◽  
pp. 59-69 ◽  
Author(s):  
Qi Zhou ◽  
Hua Qian ◽  
Li Liu
Keyword(s):  
General Hospital ◽  
Natural Ventilation ◽  
Index Patient ◽  
Dynamics Simulation ◽  
World Health ◽  
Future Design ◽  
Airborne Infection ◽  
Ventilation Rates ◽  
Hospital Wards ◽  
The Impact

Natural ventilation is believed to control airborne infection due to high ventilation rates while an undesired flow pattern may cause infection transmission in hospital wards. A computational fluid dynamics simulation was carried out in this study to investigate the impact of airflow pattern on cross infection in a real central-corridor hospital ward with natural ventilation in Nanjing, China. The simulation results demonstrate that the predicted infection risks of the downstream cubicle are up to 10.48% and 11.59% as the index patient is located in the corridor and in the opposite upstream cubicle, respectively. Under this circumstance, the downstream cubicle should be listed on the high-risk list and the central-corridor type is not recommended in a naturally ventilated ward. Measures such as keeping cubicle doors closed should be taken in order to cut off the transmission route. The results not only give direct evidence to strongly support World Health Organization’s recommendation but also suggest required amendment of the Chinese standard GB 51039-2014 to improve ventilation arrangement in general hospital wards in China. Our findings are useful for improving the future design of general hospital wards for airborne infection control.

scholarly journals The binding of carbon dioxide by horse haemoglobin

1971 ◽  
Vol 124 (1) ◽  
pp. 31-45 ◽  
Author(s):  
J. V. Kilmartin ◽  
L. Rossi-Bernardi
Keyword(s):  
Carbon Dioxide ◽  
Bohr Effect ◽  
Alkaline Ph ◽  
Amino Groups ◽  
Expected Number ◽  
Physiological Conditions ◽  
Alkaline Bohr Effect ◽  
Ph Range ◽  
The Hill ◽  
Β Chain

1. Three modified horse haemoglobins have been prepared: (i) αc2βc2, in which both the α-amino groups of the α- and β-chains have reacted with cyanate, (ii) αc2β2, in which the α-amino groups of the α-chains have reacted with cyanate, and (iii) α2βc2, in which the two α-amino groups of the β-chain have reacted with cyanate. 2. The values of n (the Hill constant) for αc2βc2, α2βc2 and αc2β2 were (respectively) 2.5, 2.0 and 2.6, indicating the presence of co-operative interactions between the haem groups for all derivatives. 3. In the alkaline pH range (about pH8.0) all the derivatives show the same charge as normal haemoglobin whereas in the acid pH range (about pH6.0) αc2βc2 differs by four protonic charges and αc2β2, α2βc2 by two protonic charges from normal haemoglobin, indicating that the expected number of ionizing groups have been removed. 4. αc2β2 and αc2βc2 show a 25% decrease in the alkaline Bohr effect, in contrast with α2βc2, which has the same Bohr effect as normal haemoglobin. 5. The deoxy form of αc2βc2 does not bind more CO2 than the oxy form of αc2βc2, whereas αc2β2 and α2βc2 show intermediate binding. 6. The results reported confirm the hypothesis that, under physiological conditions, haemoglobin binds CO2 through the four terminal α-amino groups and that the two terminal α-amino groups of α-chains are involved in the Bohr effect.

scholarly journals Multiple propane gas flow rates procedure to determine accuracy and linearity of indirect calorimetry systems : An experimental assessment of a method.

2019 ◽  
Author(s):  
Mohammad Ismail ◽  
Alsubheen A Sana'a ◽  
Angela Loucks-Atlinson ◽  
Matthew Atkinson ◽  
Liam P Kelly ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Indirect Calorimetry ◽  
Energy Production ◽  
Gas Flow ◽  
Carbon Dioxide Production ◽  
Whole Body ◽  
Gas Flows ◽  
Flow Rates ◽  
Ventilation Rates ◽  
Body Energy

Objective: Indirect calorimetry (IC) systems measure the fractions of expired carbon dioxide (FECO2) and oxygen (FEO2) recorded at the mouth in order to estimate whole body energy production (EP). The fundamental principal of IC relates to oxidative mechanisms, expressed as rate of oxygen uptake (V̇O2) and carbon dioxide production (V̇CO2). From these volumes we calculate energy production and respiratory exchange ratio which is used to estimate substrate utilization rates. The accuracy of IC systems is critical to detect small changes in respiratory gas exchanges. The aim of this technical report was to assess the accuracy and linearity of IC systems using multiple propane gas flow rates procedure. Approach: A series of propane gas with different flow rates and ventilation rates were run on three different IC systems. The actual experimental V̇O2 and V̇CO2 were calculated and compared to stoichiometry theoretical values. Results: showed a linear relationship between gas volumes (V̇O2 and V̇CO2) and propane gas flows (99.6%, 99.2%, 94.8% for the Sable, Moxus, and Jaeger metabolic carts, respectively). In terms of system error, Jaeger system had significantly (p < 0.001) greater V̇O2 (M = -0.057, SE = 0.004), and V̇CO2 (M = -0.048, SE = 0.002) error compared to either the Sable (V̇O2, M = 0.044, SE = 0.004; V̇CO2, M = 0.024, SE = 0.002) or the Moxus (V̇O2, M = 0.046, SE = 0.004; V̇CO2, M = 0.025, SE = 0.002) metabolic carts. There were no significant differences between the Sable or Moxus metabolic carts. Conclusion: The multiple flow rates approach permitted the assessment of linearity of IC systems in addition to determining the accuracy of fractions of expired gases.

scholarly journals Simulation-Based Study on the COVID-19 Airborne Transmission in a Restaurant

2020 ◽  
Author(s):  
Han Liu ◽  
Sida He ◽  
Lian Shen ◽  
Jiarong Hong
Keyword(s):  
Preventive Measures ◽  
Strong Support ◽  
Infection Risk ◽  
Exposure Index ◽  
Reverse Time ◽  
Aerosol Transport ◽  
Airborne Transmission ◽  
Local Flow ◽  
Airborne Infection ◽  
Aerosol Exposure

COVID-19 has shown a high potential of transmission via virus-carrying aerosols as supported by growing evidence. However, detailed investigations that draw direct links between aerosol transport and virus infection are still lacking. To fill in the gap, we conducted a systematic computational fluid dynamics (CFD)-based investigation of indoor air flow and the associated aerosol transport in a restaurant setting, where likely cases of airborne infection of COVID-19 caused by asymptomatic individuals were widely reported by the media. We employed an advanced in-house large eddy simulation (LES) solver and other cutting-edge numerical methods to resolve complex indoor processes simultaneously, including turbulence, flow–aerosol interplay, thermal effect, and the filtration effect by air conditioners. Using the aerosol exposure index derived from the simulation, we are able to provide a spatial map of the airborne infection risk under different settings. Our results have shown a remarkable direct linkage between regions of high aerosol exposure index and the reported infection patterns in the restaurant, providing strong support to the airborne transmission occurring in this widely-reported incidence. Using flow structure analysis and reverse-time tracing of aerosol trajectories, we are able to further pinpoint the influence of environmental parameters on the infection risks and highlight the needs for more effective preventive measures, e.g., placement of shielding according to the local flow patterns. Our research, thus, has demonstrated the capability and value of high-fidelity CFD tools for airborne infection risk assessment and the development of effective preventive measures.

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