home .Featured, Coronavirus #COVID19 Journal Club: “Intermittent occupancy combined with ventilation: An efficient strategy for the reduction of airborne transmission indoors”

#COVID19 Journal Club: “Intermittent occupancy combined with ventilation: An efficient strategy for the reduction of airborne transmission indoors”

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I expect to see more and more of this kind of article moving forward.  Moving from “here’s the virus in buildings” to “here’s an approach for dealing with it.  In this article, “Intermittent occupancy combined with ventilation: An efficient strategy for the reduction of airborne transmission indoors” the authors look at the combination of ventilation and changing occupancy patterns (via modeling).  Abstract below:

It is important that efficient measures to reduce the airborne transmission of respiratory infectious diseases (including COVID-19) should be formulated as soon as possible to ensure a safe easing of lockdown. Ventilation has been widely recognized as an efficient engineering control measure for airborne transmission. Room ventilation with an increased supply of clean outdoor air could dilute the expiratory airborne aerosols to a lower concentration level. However, sufficient increase is beyond the capacity of most of the existing mechanical ventilation systems that were designed to be energy efficient under non-pandemic conditions. We propose an improved control strategy based on source control, which would be achieved by implementing intermittent breaks in room occupancy, specifically that all occupants should leave the room periodically and the room occupancy time should be reduced as much as possible. Under the assumption of good mixing of clean outdoor supply air with room air, the evolution of the concentration in the room of aerosols exhaled by infected person(s) is predicted. The risk of airborne cross-infection is then evaluated by calculating the time-averaged intake fraction. The effectiveness of the strategy is demonstrated for a case study of a typical classroom. This strategy, together with other control measures such as continuous supply of maximum clean air, distancing, face-to-back layout of workstations and reducing activities that increase aerosol generation (e.g., loudly talking and singing), is applicable in classrooms, offices, meeting rooms, conference rooms, etc.

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David Coil

David Coil is a Project Scientist in the lab of Jonathan Eisen at UC Davis. David works at the intersection between research, education, and outreach in the areas of the microbiology of the built environment, microbial ecology, and bacterial genomics. Twitter

One thought on “#COVID19 Journal Club: “Intermittent occupancy combined with ventilation: An efficient strategy for the reduction of airborne transmission indoors”

  1. Subject: Airborne Exposure Strategy

    The FFE System is a mitigating strategy against COVID-19 airborne exposure risk in indoor environments with or without the use of a face mask.

    Personal ventilation (FFE System) is an alternative to help protect against COVID as it provides fresh and purified air directly to the breathing zone and eyes. Not only does this method in many cases improves the thermal comfort of occupants, but also protects them from cross contamination from other occupants.

    SARS-COV-2 is approximately 4.7 microns in size. Human hair is approximately 100 microns in size. Think about it? How much wind (airflow) does it take to blow away one human hair V/S a virus that is invisible to the human eye. How can a 4.7-micron size virus get close to your eyes and breathing zone when a continuous breeze of filtered air is protecting you. The FFE System is using simple physics. It is an offensive product against viruses that is safe, practical and helps dilute (weakens) the virus. Face mask changes the airflow around the face, so that instead of air entering the mouth and nose through specific paths, air enters the mouth and nose through the entire mask surface but at lower speeds. The lower speed near the face favors the inhalation of aerosols into the nose, so even though masks filter out certain numbers of particles, more particles escaping mask filtration can enter the respiratory tract. Surgical mask cannot effectively remove Sub micrometer sized aerosol particles such as aerosolized pathogens. The N95 filtering face piece respirators may not provide the expected protection level against small virions. Please see attachments and visit our website.

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