Determination of ventilation effectiveness with tracer gas methods under COVID-19 conditions
Keywords:Tracer methods, Ventilation effectiveness, SARS-Cov-2 aerosols
We report in this paper on the use of tracer gas methods and two tracer gases to determine ventilation effectiveness under COVID-19 conditions in a large concert hall in Lucerne, Switzerland. The occupancy of the concert hall was simulated by using thermal dummies and partial occupancy of people because of the COVID-19 protection regulations. Contaminants are removed very efficiently in the parquet (by factors better than with mixed ventilation). On the stage and balconies, the local ventilation effectiveness with displacement ventilation is partly comparable to mixed ventilation or even lower. The ventilation of balconies and galleries is demanding and must be carefully assessed in the case of pandemic risks. For the assessment of infection risk through aerosol transmission, a characteristic value for the entire room is not sufficient. The ventilation effectiveness and contaminant removal effectiveness depend very strongly on local boundary conditions and the prevailing flow conditions when dosed locally. The investigations show that the tracer gases sulphur hexafluoride (SF6) and 2,3,3,3-tetrafluoropropene (R1234yf) provide comparable results in determining the air exchange rate and ventilation effectiveness. With both tracer methods, it is possible to gain knowledge about the operation of the ventilation system (e.g. volume air flows, heat recovery leakage).
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