Personalized ventilation integrated with under-floor air distribution system - Protection of occupants from indoor airborne agents

Abstract

Ventilation is an effective mean of diluting indoor contaminants, including airborne agents, in the breathing zone. The idea of personalized ventilation (PV) is to supply conditioned outdoor air directly to the breathing zone of each occupant. In this research, the performance of PV combined with an under floor air distribution system (UFAD) is discussed with a focus on its efficiency of protecting occupants from indoor airborne agents. A breathing thermal manikin was used to mimic real human being. Concentration of tracer gas (SF6) discharged in the room was measured and used to study the performance of the UFAD-PV system in terms of the ability to provide occupants with 100% conditioned outdoor air. Two ventilation effectiveness indices: Personal exposure effectiveness (PEE) and personal exposure index (PEI) were used to evaluate the performance of the UFAD-PV system. It was found that enhanced performance could be achieved with UFAD-PV system when compared with ceiling supply mixing ventilation system and UFAD system alone. Temperature and flow rate of the supplied personalized air influenced the airflow interaction at the breathing zone and thus had an impact on the PEE and PEI indices, i.e. the ability of the PV to protect effectively occupants from indoor airborne infectious agents. Cooler PV supply air temperature and higher PV air flow rate always resulted in better IAQ performance at all times and contributed significantly as a strategy to protect occupants from indoor airborne agents more effectively due to the increased PEE and PEI values. © 2011 ASHRAE.