Application of the "age of air" concept in evaluating the ventilation characteristics of a cleanroom.

This study has the objective of applying the "age of air" concept and tracer gas techniques in the evaluation of ventilation characteristics of workplaces equipped with a general ventilation system. A Class I OK cleanroom was selected for this study and C02 was used as a tracer gas. After the tracer gas was released in the form of a pulse into the cleanroom, its concentration was measured as a function of time at various locations by non-dispersive infrared photometers. The average age of air at each location was then calculated from the C02 concentration data. The results show that the average age of air varied markedly from location to location, indicating that the air in the cleanroom was not well mixed. An examination of the flow pattern in the cleanroom reveals that the design of the air inlets and outlets was inappropriate. The study has demonstrated that the use of the "age of air" concept can provide a clear picture of the airflow pattern.