Effects of ceiling fan and window exhaust on aerosol transmission risk during home quarantine situation

Department of the Built Environment, National University of Singapore, Singapore

^* Corresponding author: toby_bdg@nus.edu.sg

Abstract

SARS-CoV-2 has been recognized to be airborne transmissible. With the increased transmissibility leading to increasingly reported positive cases, home quarantine is adopted for the infected patients who are not seriously ill. However, the risk of household aerosol transmission is not well studied. We conducted tracer gas experiment to simulate the exhaled virus laden aerosols from a patient under home quarantine situation inside a residential testbed. The Sulphur hexafluoride concentration (SF_6,conc) was measured both inside and outside the quarantine room under various scenarios including, (i) air-conditioning (AC) vs natural ventilation (NV), (ii) operation of ceiling fan, and (iii) operation of window exhaust fan. The ratio of outside-to-inside SF_6,conc (O/I_SF6) was an indicator for potential exposure of occupants in the same household. Our findings showed, without an exhaust fan, the in-room SF_6,conc in AC settings was 4 times higher than in the NV scenarios. Meanwhile, we found the exhaust fan was effective in reducing the O/I_SF6 in the AC scenarios (with or without ceiling fan), but its function was diminished in the NV setting with ceiling fan. We suspected the effectiveness of exhaust fan was reduced by air infiltration from other window openings in NV situation. Meanwhile, the operation of ceiling fan continuously pushing tracer gas outwards from the quarantine room through the door gap. Our results suggested that natural ventilation with windows open or switching on a window exhaust fan could reduce aerosol transmission risk from the quarantine room. This study provides useful evidence in recommending low risk ventilation strategies for home quarantine situations.