![]() ![]() If the relevant boundary conditions for these disturbing influences are unknown, the estimation is regarded to be even more critical.įor individual considerations and higher accuracies, experimental studies examine the effects of ventilation measures on airborne infections. In reality, however, these are superimposed by disturbance effects, which might be critical regarding neighbor infection risks. In ideal theory, there would occur only unobjectionable vertical buoyancy flows. Furthermore, existing disturbance influences (leaks and opening of windows/doors, downdrafts, etc.) have to be considered for the respective ventilation type.ĭisplacement ventilation concepts, often applied in large halls, impede estimations of virus transmission to neighbors. These transient effects cannot be represented by a simple calculation model. Depending on the meteorological boundary conditions such as wind velocity, natural ventilation can be classified between mixed ventilation and displacement ventilation. In practice, different ventilation principles-natural ventilation and mechanical ventilation (mixing ventilation, displacement ventilation, downward ventilation)-are applied, depending on the type of use and the occupancy density of the room. Even for small to medium scales, the calculation models may not resolve aerosol dispersion appropriately. In reality, the condition of ideal mixed ventilation is impossible to achieve (finite velocity for distributing locally released substances), especially for larger rooms. ![]() Often, these are based on idealised assumptions (e.g., ideal mixed ventilation). įor fast and simple assessments, many calculation models regarding the infection risk of SARS-CoV-2 in indoor environments exist. The ongoing pandemic teaches us that the implementation of appropriate ventilation measures can significantly reduce indoor infection risks. Two examples (a two-person office and a classroom) show how practical both methods are and how the principle is applicable for different types and sizes of rooms. This is the only way to ensure that the comparison of different ventilation measures described above is reliable. One key aspect of the study is to prove that the requirement of concordant results of both methods is fulfilled. Surrounding substance concentration measurements identify the neighborhood exposure. The release of a controlled rate of either trace gas or particles simulates an infectious person releasing virus material. For an accurate assessment of air purifiers based on filtration, a surrogate particle method is appropriate. ![]() ![]() A trace gas method is suitable for mechanical and natural ventilation with outdoor air exchange. Hence, a suitable, simple and generalized experimental set up for identifying the spatial and temporal infection risk for different ventilation measures is more qualified even with unknown boundary conditions. Effortful computational fluid dynamics demand detailed boundary conditions for accurate calculations of indoor airflows, which are often unknown. A first-time comparison of mechanical/natural ventilation and air purification with regard to infection risks is enabled. This study introduces a principle that unifies two experimental methods for evaluating airborne indoor virus-transmissions adapted to several ventilation measures. ![]()
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