Indoor Air Quality Impacts of Ventilation Ducts: Ozone Removal and Emissions of Volatile Organic Compounds
The concentrations of contaminants in the supply air of mechanically ventilated buildings may be altered by pol-lutant emissions from and interactions with duct materi-als. We measured the emission rate of volatile organic com-pounds (VOCs) and aldehydes from materials typically found in ventilation ducts. The emission rate of VOCs per exposed surface area of materials was found to be low for some duct liners, but high for duct sealing caulk and a neo-prene gasket. For a typical duct, the contribution to VOC concentrations is predicted to be only a few percent of com-mon indoor levels. We exposed selected materials to ~100-ppb ozone and measured VOC emissions. Exposure to ozone increased the emission rates of aldehydes from a duct liner, duct sealing caulk, and neoprene gasket. The emission of aldehydes from these materials could increase indoor air concentrations by amounts that are as much as 20% of odor thresholds. We also measured the rate of ozone uptake on duct liners and galvanized sheet metal to predict how much ozone might be removed by a typical duct in ventilation systems. For exposure to a constant ozone mol fraction of 37 ppb, a lined duct would initially remove ~9% of the ozone, but over a period of 10 days the ozone removal effi-ciency would diminish to less than 4%. In an unlined duct, in which only galvanized sheet metal is exposed to the air-stream, the removal efficiency would be much lower, ~0.02%. Therefore, ducts in ventilation systems are unlikely to be a major sink for ozone. The emission rate of volatile organic compounds (VOC) and aldehydes from materials typically found in ventilation ducts was measured. The rate of ozone uptake on duct liners and galvanized sheet metal was also measured to predict the degree of ozone removal by a typical duct in ventilation systems. It is suggested that the ozone removal efficiency in an unlined duct would be much lower as compared to a lined duct.
G. Morrison et al., "Indoor Air Quality Impacts of Ventilation Ducts: Ozone Removal and Emissions of Volatile Organic Compounds," Journal of the Air and Waste Management Association, Air and Waste Management Association, Oct 1998.
Civil, Architectural and Environmental Engineering
Keywords and Phrases
Galvanized Metal; Pipe Linings; Ventilation Ducts; Ozone; Volatile organic compounds
Article - Journal
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