Air quality by VAV HVAC system before and after cleaning. Case study.

Since the study by P.O Fanger (1988) [1] we know that the Heating Ventilating and AirConditioning (HVAC) system could be responsible for a large amount of indoor air pollutionand Sick Build Syndrome (SBS). The pollution could become from filters, cooling coils anddust accumulated on duct surfaces in systems with poor maintenance.While the importance of maintenance of air handling units and replacement of air filters iswell recognized in Portugal, the cleanliness of ducts is sometimes forgotten. Research isneeded on standard methods to measure the surface pollution and criteria to appreciate thecleanliness of duct surface, as well as the requirement for duct disinfection after an adequatemechanical cleaning.In this paper the results of a study undertaken in a 9 year old office building in Lisbon areawith a VAV system are presented, including the methods used to measure the air quality andthe surface pollution. The results show that mechanical cleaning contributes to a largereduction in dust concentration in surfaces and in the air supplied to spaces. The concentrationof bacteria and moulds in surfaces and in the air was quite low and therefore in this buildingchemical disinfection is not required.A continuous audit of the system is recommended (with visual inspection for instance andsome measurements) to choose between cleaning some components or the complete systemand some suggestions about the criteria to be adopted before cleaning ducts are also offered.