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Indoor ultrafine particles of outdoor origin: importance of window opening area and fan operation condition.



Dong H. Rim, Lance L. Wallace, Andrew K. Persily


Airborne ultrafine particles (UFP) have been associated with human mortality and morbidity. Human exposure to ambient UFP occurs indoors due to entry of UFP into buildings. This study investigates UFP entry as a function of building operating conditions such as central fan operation and window position. Indoor and outdoor UFP concentrations along with air change rates were continuously measured in a full-scale test building. Estimates of infiltration factor, penetration coefficient and deposition rate have been made for a range of particle sizes from 4 nm to 100 nm. The results show that UFP infiltration factor varies with particle diameter, window position, air change rate, and central fan operation. UFP entry into the building increases as air change rate and particle size increase. Larger window openings lead to higher infiltration factors due to larger extent of particle penetration into the building. Comparing the fan operation mode (on vs. off), infiltration factors were lower with fan-off condition than fan-on condition, which was likely caused by additional particle deposition loss to the furnace filter and duct surfaces.
Environmental Science and Technology


ultrafine particles, infiltration factor, indoor-outdoor relationship, penetration, deposition, building operating condition


Rim, D. , Wallace, L. and Persily, A. (2013), Indoor ultrafine particles of outdoor origin: importance of window opening area and fan operation condition., Environmental Science and Technology, [online], (Accessed July 14, 2024)


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Created February 5, 2013, Updated February 19, 2017