Experimental Methods of Investigating Airborne Indoor Virus-Transmissions Adapted to Several Ventilation Measures

Abstract

This study introduces a principle that unifies two experimental methods for evaluating airborne indoor virus-transmissions adapted to several ventilation measures. A first-time comparison of mechanical/natural ventilation and air purification with regard to infection risks is enabled. Effortful computational fluid dynamics demand detailed boundary conditions for accurate calculations of indoor airflows, which are often unknown. 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. A trace gas method is suitable for mechanical and natural ventilation with outdoor air exchange. For an accurate assessment of air purifiers based on filtration, a surrogate particle method is appropriate. The release of a controlled rate of either trace gas or particles simulates an infectious person releasing virus material. Surrounding substance concentration measurements identify the neighborhood exposure. One key aspect of the study is to prove that the requirement of concordant results of both methods is fulfilled. This is the only way to ensure that the comparison of different ventilation measures described above is reliable. 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.

Experimental Device to Evaluate Aerosol Dispersion in Venues

“…8 It is known that the implementation of appropriate ventilation measures can significantly reduce the risk of indoor infections. 9 Displacement ventilation aims to keep the fresh and polluted air separated. 10 A stream of fresh air from the floor is used to displace the waste air, which rises to the ceiling by buoyant force and is then removed from the room via air vents.…”

“…1 For individualized considerations and high levels of accuracy, experimental studies must be conducted to examine the efficacy of ventilation measures. 9 Several strategies have been proposed for investigating aerosol distribution in indoor venues, each with their own advantages and limitations.…”

“…A tracer gas is emitted into the venue and local concentrations are measured using infrared spectrometers. 9 This measurement technique is convenient for both small and big venues with outside air exchange. However, the room needs to be completely free from the tracer gas of potential previous measurements to avoid contamination.…”

“…Also, tracer gases cannot be filtered, making this method unsuitable for evaluating air purifiers that rely on filtration. 9 Another method to evaluate the spread of aerosols is the use of tracer gases. A tracer gas is emitted into the venue and local concentrations are measured using infrared spectrometers.…”

Ventilation and Indoor Air Quality

“…The proposed window windcatcher has been shown to improve both thermal comfort and indoor air quality. Another interesting paper by Siebler et al [18] evaluated indoor airborne virus transmissions using two methods (a generalized experimental set up and a trace gas method) for several ventilation measures. Readers will enjoy a review of indoor air quality cleansing technologies by Mata et al [19].…”