The comparison between air change efficiency and contaminant removal effectiveness under some typical air flow conditions in the room ventilated mechanically.

There are many indices to evaluate the ventilation characteristics of the ventilated rooms. These indices are classified into air change efficiency and contaminant removal effectiveness. In order to know how to use many indjces for a good understanding of the characteristics of the concerned ventilation system, the values of various efficiencies under some typical air flow conditions with isothermal condition are compared. The local mean age distributions and local contaminant concentrations are measured with tracer gas technique in a scaled model of the room ventilated mechanically. Four typical air flow conditions are made inside the enclosure. Two conditions are of high velocity type, and the other two condition are of low velocity type. The ceiling based type and the underfloor type are elected as the typical ventilation system. The distribution of local air change index and local air quality index were investigated. Then the relation hip between local air change index and local air quality index was examined. It is turned out that this relationship express a unique and interesting feature for each ventilation type. And it is confirmed that air change efficiency and contaminant removal effectiveness are also important indices to evaluate the quality of ventilation efficiency.