Using portable air cleaners to restrict airborne transmission in an open plan office – a field measurement and CFD study

¹ Department of Mechanical Engineering, School of Engineering, Aalto University, Espoo, Finland
² Department of Civil Engineering and Architecture, Tallinn University of Technology, Tallinn, Estonia
³ Department of Civil Engineering, School of Engineering, Aalto University, Espoo, Finland
⁴ Department of HVAC, College of Urban Construction, Nanjing Tech University, Nanjing, China

^* Corresponding author: simo.kilpelainen@aalto.fi

Abstract

Airborne transmission of pathogens has been widely studied in the aftermath of the recent COVID-19 pandemic since it is one of the most important routes for infection spreading. This study focused on open plan offices which have become very popular due to their flexibility. Tracer gas (CO2) field measurements were performed to assess the local point source contaminant removal effectiveness of the ventilation system. CFD simulations were performed to investigate the difference in contaminant concentration and removal effectiveness between basic ventilation and added portable air purifiers. Two air purifiers were simulated, with the total airflow of the purifiers equalling that of the supply air. This airflow, which was lower than the recommended >2 times supply airflow, was chosen to keep the airflows of the individual units at a reasonable level, avoiding excess draught and noise. In the simulations, three locations for the infected person were studied, bringing the total number of cases to six. The results showed that the location of the infector had a significant influence on the airborne spread. With air purifiers, the contaminant spread was limited to the near the infector. To conclude, air purifiers – even at airflows lower than recommendation – are efficient in reducing contaminant spreading in an open plan office.