Safe CO2 threshold limits for indoor long-range airborne transmission control of COVID-19

Lyu, Xiaowei; Luo, Zhiwen; Shao, Li; Awbi, Hazim; Piano, Samuele Lo

doi:10.1016/j.buildenv.2022.109967

Cited by 9 publications

(7 citation statements)

References 52 publications

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“…In this study, the CO 2 concentration was classified as high or low based on a cut-off of 1,000 ppm; however, for future social implementation, a method to adaptively calculate the excess CO 2 threshold based on the number of occupants, community prevalence, and activity level should be adopted [ 44 ].…”

Section: Discussionmentioning

confidence: 99%

Monitoring the ventilation of living spaces to assess the risk of airborne transmission of infection using a novel Pocket CO2 Logger to track carbon dioxide concentrations in Tokyo

Ishigaki,

Yokogawa

2024

PLoS ONE

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We employed carbon dioxide (CO2) concentration monitoring using mobile devices to identify location-specific risks for airborne infection transmission. We lent a newly developed, portable Pocket CO2 Logger to 10 participants, to be carried at all times, for an average of 8 days. The participants recorded their location at any given time as cinema, gym, hall, home, hospital, other indoors, other outgoings, pub, restaurant, university, store, transportation, or workplace. Generalized linear mixed model was used for statistical analysis, with the objective variable set to the logarithm of CO2 concentration. Analysis was performed by assigning participant identification as the random effect and location as the fixed effect. The data were collected per participant (seven males, four females), resulting in a total of 12,253 records. Statistical analysis identified three relatively poorly ventilated locations (median values > 1,000 ppm) that contributed significantly (p < 0.0001) to CO2 concentrations: homes (1,316 ppm), halls (1,173 ppm), and gyms (1005ppm). In contrast, two locations were identified to contribute significantly (p < 0.0001) to CO2 concentrations but had relatively low average values (<1,000 ppm): workplaces (705 ppm) and stores (620 ppm). The Pocket CO2 Logger can be used to visualize airborne infectious transmission risk by location to help guide recommendation regarding infectious disease policies, such as restrictions on human flow and ventilation measures and guidelines. In the future, large-scale surveys are expected to utilize the global positioning system, Wi-Fi, or Bluetooth of an individual’s smartphone to improve ease and accuracy.

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Section: Discussionmentioning

confidence: 99%

Monitoring the ventilation of living spaces to assess the risk of airborne transmission of infection using a novel Pocket CO2 Logger to track carbon dioxide concentrations in Tokyo

Ishigaki,

Yokogawa

2024

PLoS ONE

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“…With respect to this, it is recommended for many spaces that the supply of outside (fresh) air be a minimum of 10 L/s per person, which is generally enough to ensure a maximum CO 2 concentration of 800-1000 ppm [117]. Since the COVID-19 pandemic, CO 2 concentration has increasingly been used as a surrogate marker of respiratory aerosol concentration inside buildings [114,[118][119][120][121]. Ventilation air introduced from outside dilutes the exhaled CO 2 produced by building occupants, so the CO 2 concentration can be used to determine whether or not a space is adequately ventilated.…”

Section: Droplet Transmissionmentioning

confidence: 99%

Airborne Transmission of SARS-CoV-2: The Contrast between Indoors and Outdoors

Beggs,

Abid,

Motallebi

et al. 2024

Fluids

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COVID-19 is an airborne disease, with the vast majority of infections occurring indoors. In comparison, little transmission occurs outdoors. Here, we investigate the airborne transmission pathways that differentiate the indoors from outdoors and conclude that profound differences exist, which help to explain why SARS-CoV-2 transmission is much more prevalent indoors. Near- and far-field transmission pathways are discussed along with factors that affect infection risk, with aerosol concentration, air entrainment, thermal plumes, and occupancy duration all identified as being influential. In particular, we present the fundamental equations that underpin the Wells–Riley model and show the mathematical relationship between inhaled virus particles and quanta of infection. A simple model is also presented for assessing infection risk in spaces with incomplete air mixing. Transmission risk is assessed in terms of aerosol concentration using simple 1D equations, followed by a description of thermal plume–ceiling interactions. With respect to this, we present new experimental results using Schlieren visualisation and computational fluid dynamics (CFD) based on the Eulerian–Lagrangian approach. Pathways of airborne infection are discussed, with the key differences identified between indoors and outdoors. In particular, the contribution of thermal and exhalation plumes is evaluated, and the presence of a near-field/far-field feedback loop is postulated, which is absent outdoors.

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“…34 Moreover, more researchers insist that carbon dioxide (CO 2 ) can reflect the trend of bioaerosol concentration, and strongly recommend that CO 2 concentration be used for infection risk-based monitoring. [35][36][37][38][39] Research has shown that particulate matter pollution is a serious global risk factor to human health among all key pollutants, 40 and PM 2.5 levels are positively correlated with COVID-19 exposure risk, 25 as fine particles (FPs) and ultrafine particles (UFPs) have small particle sizes and large specific surface areas, making them easy to adsorb metals, microorganisms, and other pollutants. 40 Particles may play a role in the differential distribution and propagation rate of SARS-CoV-2.…”

Section: Introductionmentioning

confidence: 99%

Prediction models of bioaerosols inside office buildings: A field study investigation

Jiang

Gong

et al. 2023

Building Services Engineering Research and Technology

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Bioaerosols formed by microorganisms in the air directly affect people’s health. The air quality in an office building in Shenzhen, China, is investigated and pollutant levels measured on 36 occasions; six times for each of six indoor spaces. A relationship between indoor bioaerosols and environmental factors was determined using both linear regression analysis and Poisson regression analysis. Our results and analysis indicate that linear regression is a poor predictor for the concentration of bioaerosols based on a single indicator. In contrast, Poisson regression can better predict the concentration of bioaerosols, and PM10 may be the indicator with the greatest impact on bioaerosols. As a result, a simple, fast, and low-cost online monitoring method for monitoring indoor bioaerosols is developed and reported. Our paper provides first-hand basic data to predict the indoor bioaerosol concentration and helps to formulate appropriate monitoring guidelines. The proposed method offers more practical values compared to existing studies as our prediction model facilitates estimation of the concentration of bioaerosols at low cost. Additionally, due to the current maturity and low cost of indoor environmental sensors, the proposed method is suitable for large-scale deployment for most buildings. Practical application Based on measurement data from a real office building, our investigation explores the relationship between indoor microorganisms and building environmental indicators through a combination of probability analysis and actual measurement. We establish a novel indoor microbial prediction model using the Poisson regression model. Our work presents an effective, low-cost, method for estimating the concentration of bioaerosols and discusses the possibility for large-scale deployment of microbial monitoring equipment inside buildings which may then support real-time monitoring of indoor microbial concentration to provide healthy indoor environments for personnel.

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Safe CO2 threshold limits for indoor long-range airborne transmission control of COVID-19

Cited by 9 publications

References 52 publications

Monitoring the ventilation of living spaces to assess the risk of airborne transmission of infection using a novel Pocket CO2 Logger to track carbon dioxide concentrations in Tokyo

Monitoring the ventilation of living spaces to assess the risk of airborne transmission of infection using a novel Pocket CO2 Logger to track carbon dioxide concentrations in Tokyo

Airborne Transmission of SARS-CoV-2: The Contrast between Indoors and Outdoors

Prediction models of bioaerosols inside office buildings: A field study investigation

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