Performance Evaluation of Personalized Ventilation - Personalized Exhaust (PV-PE) System in Air-conditioned Healthcare Settings

Abstract

Several severe acute respiratory syndrome outbreaks in recent 10 years have highlighted the issue of short range aerosol transmission between healthcare workers and the patients. Concerns about the ventilation system design in healthcare centres in the field of control of airborne transmission of infection have become topical and important. Personalized Ventilation (PV) has been introduced in indoor air distribution for more than a decade and the concept involves delivering 100% conditioned outdoor air directly to the occupant breathing zone. The primary aim of a PV system is to supply fresh air to the breathing zone to enhance Inhaled Air Quality. At the same time, it can also be seen as a solution to prevent the spread of contaminated air. Whilst a conventional PV system would fulfil most of these requirements, it may not be able to adequately prevent the spread of contaminated air as the PV air would go past an infected person and mix with the room air. In order to maximize the advantages of a PV system in delivering personalized air to the breathing zone, it is interesting to explore the use of a personalized exhaust device that is integrated with the chair and assists in pulling the PV air flow towards the seated person. Not only is the inhaled air quality improved further but the exhaled contaminated air is extracted locally and its spread into the room air is minimized by adding the local exhaust working together with the PV system. Experimental study using tracer gases have been conducted to evaluate the performance of this novel PV-PE system in conjunction with two different background ventilation systems. Two types of PE: top-PE and shoulder-PE are evaluated and four different arrangements between the Healthy Person and the Infected Person were studied. The results indicate that there is a potential for improving inhaled air quality by having the combined PV-PE system to pull the air towards the seated person, especially under displacement ventilation. It also shows that this kind of personalized exhaust can prevent the spread of contaminated air by exhausting the exhaled air directly before it mixes with the room air; especially the top-PE has a better performance than shoulder-PE. Furthermore, the use of PE is a more efficient way to protect the healthy person than using PV.