Effect of Intermittent Personalized Ventilation on Coughed Particles Dispersion in an Office Space and Resulting Cross Contamination

Abstract

Abstract The transmission of infectious respiratory diseases has been a topic of broad interest for decades. It is largely influenced by the ventilation in the space, especially localized ventilation near the infection source. One energy-friendly ventilation technique that has been extensively investigated in contaminants transmission is Personalized Ventilation (PV), which delivers cool clean air directly towards the breathing zone of the user, procuring acceptable levels of thermal comfort and breathable air quality. However, when used by an infected person, it might amplify the dispersion of the expiratory droplets, increasing the risk of airborne cross-infection. Some PV applications varied the supplied cool clean air intermittently in order to enhance occupants’ thermal comfort and improve energy performance. Such system operation is referred to as Intermitted PV (I-PV). Nonetheless, the effect of such oscillatory jet on airborne diseases dispersion has not been assessed in literature to the authors’ knowledge. In this work, the impact of integrating I-PV with mixed ventilation on cross-contamination is investigated for the case where an infected user is coughing. The I-PV is considered to operate at an average flowrate of 10 l/s, with a minimum of 4 l/s at a typical frequency of 0.94 Hz. The infected person is considered seated in a tandem (i.e. back-to-face) position with respect to a healthy person, located at a distance of 1.5 m and not using PV. This reflects the worst-case scenario where the healthy person is not protected by PV. A validated computational fluid dynamics (CFD) model is used to assess the cross-contamination between the occupants. A comparison between I-PV and steady PV (S-PV) of constant flowrate of 10 l/s is conducted to highlight the influence of I-PV on contaminants dispersion in the space and the resulting exposure level of a healthy occupant. Results showed that the use of I-PV reduced the exposure levels of the healthy occupant in comparison to S-PV.