In the beginning of 1998 the European project, AIRLESS, was started to develop strategies,principles and protocols to improve and control the petiormance of HVAC-systems and itscomponents for the incorporation in codes and guidelines. The project is divided in 6 tasks.The Hermann-Rietschel-Institute deals with the second task of the project, the maintenance ofHVAC-systems. People stay approximately 90% of their lifetime in enclosed rooms. Theserooms are often served by HVAC systems. In recent years poor indoor climate has causedhealth problems in buildings.
A humidity controlled air flow terminal device works as a humidity sensor : its openingsurface varies according to relative humidity inside a room in order to match air flow rate topollution. These components are fouling up when used during several months.In a laboratory, an air flow with a high rate of particules is fouling up five identical air devicesin a few hours. Considering a constant relative humidity, the impacts on two devices aresimilar : it seems that artificial fouling tests can be reproduced.