Measurement and characterization of particulate and bioaerosol pollutants in indoor air

Suspended particulate matter and bioaerosols are important indoor air quality (IAQ) contaminants that may have adverse health effects on building occupants. This study addresses the characterization of aerosol pollutants in large, mechanically ventilated buildings. Characterization of IAQ can be difficult in large buildings due to the inherent variability in distribution of particulate matter and bioaerosols, the many and diverse uses of interior spaces, changes in occupant activities over time, and the large and complex heating, ventilating and air conditioning (HVAC) systems. This study evaluates aerosol measurement methods, sampling strategies, and data interpretation techniques including source apportionment. Comprehensive field investigations in office and other buildings are used to evaluate these measurements, as well as mathematical and statistical models.; Principal conclusions of the study include the following: Measurements of airborne and bulk (surface) concentrations of particulate matter in HVAC system ducts and components can complement measurements in the occupied zone and outdoor air and should be utilized in IAQ field investigations. Shrouded probe samplers are well suited to sampling in the flowing air streams of HVAC ducts and can eliminate the need for isokinetic sampling. Airborne bioaerosol concentrations in the HVAC system and occupied zone should be low ({dollar}<{dollar}200 cfu m{dollar}sp{lcub}-3{rcub}).{dollar} High microbial concentrations in bulk samples collected from HVAC systems may identify potential emission sources, however, this does not necessarily indicate that indoor air is significantly or frequently contaminated. Airborne concentrations of particulate matter in ducts can indicate the air quality delivered to occupants. Return air concentrations may not be representative of those found in indoor air although these measurements can be used to estimate HVAC system performance, e.g., ventilation effectiveness. To obtain representative results, sampling strategies should account for the autocorrelation of pollutant levels, air exchange rate, and ventilation effectiveness. Occupant activities can increase concentrations of larger particles and partly explain the variability of concentrations at certain locations. These conclusions are particularly applicable to particulate and bioaerosol measurements in large and mechanically ventilated office buildings.