Air quality and ductwork contamination: survey methodology and acceptable values.

Several problems can occur if the design, installation and maintenance of HVAC systems fail to follow appropriate standards. These include excessive installation and maintenance costs as well as hygiene problems produced by dust deposition and accumulation. There is no proper set of standards for biological risk assessments to prevent ventilation system pollution. All there is are a few guidelines on limit values of bacterial and fungal air concentration. Using data collected on the hygienic conditions of ventilation systems, the results of a study of 17 HVAC systems (7 office buildings and 10 hospitals) is discussed.