Sheltering as a protective measure against airborne virus spread (original) (raw)
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VIRUS AEROSOLS: ON THE BEHAVIOR IN CONFINED SPACES: SCHOOLS, STUDIOS, CONCERTS & AIRPLANES
J. Terrestrial Electrostatics & Hydroactivity, 2021
The virus is getting closer. If you live in rural areas, you are less concerned with reports about overcrowded hospitals. This is not a strange reaction. After all, politicians had the same reaction when the epidemic was still in Wuhan/ China. And even when the epidemic turned into a pandemic, many people suddenly appeared to be specialists in virus behavior. Especially the masks were the subject of intensive discussions in the mass media. Unfortunately, the virus is insensitive to these arguments. It follows its own rapid progress, ignoring tests and vaccinations, by mutating. Suddenly, a child in your community is contaminated, after which the whole family and co-residents have to be tested. Next is the question: how does your family doctor protect her or him self? And, what to do to have your hair cut safely at your hairdresser's? Research has clearly shown that the chance of infection increases as the air becomes cleaner. This is not only the result of gravity but also of the number of people breathing in and out. Quietly sitting together reduces the number of PM2.5 particles through filtration and increases so the spread of the virus. In this "Teaching Paper," we will discuss the different forms of confinement: a school; a painter's studio; a music performance place; and a passenger plane. For better comprehension for everyone interested in the subject, illustrations are added.
Environmental Research, 2022
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Indoor Air
In a virus pandemic context, buildings ventilation has been recognized as a solution for preventing transmission of the virus in aerosolized form. The impact of the widespread recommendation of window opening and sealing door on ventilation circuits needs to be considered with a multizone approach. We modeled the airflow distribution in a building where people are isolating in a pandemic context, including one infected person. We analyzed the impact of opening the window and sealing the door in the quarantine room on exposures and probability of infection for occupants of the flat and of adjacent flats. In order to study the sensitivity of the results, we tested three ventilation systems: balanced, exhaust-only, and humidity-based demand-controlled, and several window-and door-opening strategies. When the door of the quarantine room is sealed, we observe that opening the window in the quarantine room always results in increased exposure and probability of infection for at least one other occupant, including in neighbors' apartments. When all internal doors are opened, we observe moderate impacts, with rather an increase of exposure of the occupants of the same apartments and of their probability of infection, and a decrease for the occupants located in other apartments. Based on the analysis on the airflows distribution in this case study, we conclude that sealing the internal door has more influence than opening the window of the quarantine room, whatever the ventilation system. We observe that this widespread recommendation to open the window of a quarantine room and to seal the door is based on the consideration of a single zone model. We illustrate the importance of moving from such a single zone approach to a multizone approach for quantifying ventilation and airing impacts in multizone buildings as residences in order to prevent epidemics of viruses such as SARS-CoV-2. It highlights the need of air leakage databases. K E Y W O R D S aerosolized virus, airflow distribution, indoor air quality, public health, residences, virus infections, window opening This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Environmental Effects on Viable Virus Transport and Resuspension in Ventilation Airflow
Viruses, 2022
To understand how SARS-CoV-2 spreads indoors, in this study bovine coronavirus was aerosolized as simulant into a plexiglass chamber with coupons of metal, wood and plastic surfaces. After aerosolization, chamber and coupon surfaces were swiped to quantify the virus concentrations using quantitative polymerase chain reaction (qPCR). Bio-layer interferometry showed stronger virus association on plastic and metal surfaces, however, higher dissociation from wood in 80% relative humidity. Virus aerosols were collected with the 100 L/min wetted wall cyclone and the 50 L/min MD8 air sampler and quantitated by qPCR. To monitor the effect of the ventilation on the virus movement, PRD1 bacteriophages as virus simulants were disseminated in a ¾ scale air-conditioned hospital test room with twelve PM2.5 samplers at 15 L/min. Higher virus concentrations were detected above the patient’s head and near the foot of the bed with the air inlet on the ceiling above, exhaust bottom left on the wall. B...
Outdoor Airborne Transmission of Coronavirus Among Apartments in High-Density Cities
Frontiers in Built Environment, 2021
The coronaviruses have inflicted health and societal crises in recent decades. Both SARS CoV-1 and 2 are suspected to spread through outdoor routes in high-density cities, infecting residents in apartments on separate floors or in different buildings in many superspreading events, often in the absence of close personal contact. The viability of such mode of transmission is disputed in the research literature, and there is little evidence on the dose–response relationship at the apartment level. This paper describes a study to examine the viability of outdoor airborne transmission between neighboring apartments in high density cities. A first-principles model, airborne transmission via outdoor route (ATOR), was developed to simulate airborne pathogen generation, natural decay, outdoor dispersion, apartment entry, and inhalation exposure of susceptible persons in neighboring apartments. The model was partially evaluated using a smoke tracer experiment in a mock-up high-density city si...
Control of airborne infectious disease in buildings: Evidence and research priorities
Indoor Air, 2021
The evolution of SARS-CoV-2 virus has resulted in variants likely to be more readily transmitted through respiratory aerosols, underscoring the increased potential for indoor environmental controls to mitigate risk. Use of tight-fitting face masks to trap infectious aerosol in exhaled breath and reduce inhalation exposure to contaminated air is of critical importance for disease control. Administrative controls including the regulation of occupancy and interpersonal spacing are also important, while presenting social and economic challenges. Indoor engineering controls including ventilation, exhaust, air flow control, filtration, and disinfection by germicidal ultraviolet irradiation can reduce reliance on stringent occupancy restrictions. However, the effects of controls-individually and in combination-on reducing infectious aerosol transfer indoors remain to be clearly characterized to the extent needed to support widespread implementation by building operators. We review aerobiologic and epidemiologic evidence of indoor environmental controls against transmission and present a quantitative aerosol transfer scenario illustrating relative differences in exposure at close-interactive, room, and building scales. We identify an overarching need for investment to implement building controls and evaluate their effectiveness on infection in well-characterized and real-world settings, supported by specific, methodological advances. Improved understanding of engineering control effectiveness guides implementation at scale while considering occupant comfort, operational challenges, and energy costs. Practical Implications Emerging variants of SARS-CoV-2 have led to increased infectivity by the aerosol inhalation mode and increasing infection incidence. Even in the absence of symptoms, people infected with respiratory viruses can exhale infectious aerosols that can be inhaled, deposit in the respiratory tract, and initiate infection. Indoor environments are the predominant settings for respiratory infection transmission because people spend most of their time indoors, and because concentrations of infectious aerosols can accumulate, resulting in hazardous inhalation exposure at close-interactive, room (even at distances much greater than two meters), and building scales. We illustrate the relative respiratory aerosol transfer and exposure at these scales, provide an overview of the scientific basis of engineering controls that can be deployed in buildings to reduce transfer between people, and outline priority research directions to guide widespread implementation of controls in buildings.
Sheltering effects of buildings from biological weapons
Science & Global Security, 2000
Methods for modeling indoor air pollution are used to determine the degree of protection offered by buildings against airborne biological agents. The factors that determine the sheltering effectiveness of a particular building (air exchange rates, particle deposition rates, environmental decay of agents, and filter efficiencies) are considered. Representative values for each of these parameters are determined from available information. The protection offered by an average U.S. home is computed, and the effects of modest civil defense measures are quantified.
2020
We develop a spatially dependent generalisation to the Wells–Riley model [1] and its extensions applied to COVID-19, for example [2], that determines the infection risk due to airborne transmission of viruses. We assume that the concentration of infectious particles is governed by an advection–diffusion–reaction equation with the particles advected by airflow, diffused due to turbulence, emitted by infected people and removed due to the room ventilation, inactivation of the virus and gravitational settling. We consider one asymptomatic or presymptomatic infectious person who breathes or talks, with or without a mask and model a quasi-3D setup that incorporates a recirculating air-conditioning flow. A semi-analytic solution is available and this enables fast simulations. We quantify the effect of ventilation and particle emission rate on the particle concentration, infection risk and the ‘time to probable infection’ (TTPI). Good agreement with CFD models is achieved. Furthermore, we ...