The age of the air in a room is normally determined either from a pulse response or from a step change response (up or down). There are a certain number of problems involved in applying these two theoretical models, especially those associated with the duration of the injection, which must either be infinitely short or infinitely long. A hybrid method that consists of injecting a known quantity of tracer for a given time offers the advantages of both methods.
Comfort evaluations cover air quality, thermal, visual and acoustic comfort. Today, only few computer programs allow for the integrated evaluation of several or all relevant parameters. Heat transport, ventilation as well as lighting in a room are influenced by each other. Therefore they should be integrally modelled. As a part of the IEA-ECBCS Annex 23 'Multizone Airflow Modelling', such a coupling has been realised by integrating the air flow and contaminant transport simulation code of CoMIS into the building and systems simulation code TRNSYS.
This report is from a study of the performance of eight exhaust systems of a large medical center in Tennessee. The mechanical contractor of the project initiated this study when confronted with a claim of unacceptable deficiencies in all building exhaust systems. These systems were reportedly exhausting 32% to 43% less than design airflow as a consequence of excessive leakage in the duct system.
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