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Mechanical Ventilation in a Residential Building Brings Outdoor NOx Indoors with Limited Implications for VOC Oxidation from NO3 Radicals



Michael F. Link, Jienan Li, Jenna Ditto, Han Huynh, Jie Yu, Stephen Zimmerman, Andrew Shore, Katelyn Rediger, Jonathan Abbatt, Lauren Garofalo, Delphine Farmer, Dustin Poppendieck


Energy-efficient residential building standards require the use of mechanical ventilation systems that replace indoor air with air from the outdoors. Transient outdoor pollution events can be transported indoors via the mechanical ventilation system, and other outdoor air entry pathways, and impact indoor air chemistry. In the spring of 2022, we observed elevated levels of NOx (NO + NO2), that originated outdoors, entering the National Institute of Standards and Technology (NIST) Net-Zero Energy Residential Test Facility through the mechanical ventilation system. Using measurements of NOx, ozone (O3), and volatile organic compounds (VOCs) we modeled the effect of the outdoor-to-indoor ventilation of NOx pollution on the production of nitrate radical (NO3), a potentially important indoor oxidant. We evaluated how VOC oxidation chemistry was affected by NO3 during NOx pollution events compared to background conditions. We found that nitric oxide (NO) pollution introduced indoors titrated O3 and inhibited the modeled production of NO3. NO ventilated indoors also likely ceased most gas-phase VOC oxidation chemistry during plume events. Only through the artificial introduction of O3 to the ventilation duct during a NOx pollution event (i.e. when O3 and NO2 concentrations were high relative to typical conditions) were we able to measure compounds indicating NO3 was impacting VOC oxidation chemistry.
Environmental Science and Technology


indoor air chemistry, ventilation, net-zero energy residential building, VOC oxidation, ozone


Link, M. , Li, J. , Ditto, J. , Huynh, H. , Yu, J. , Zimmerman, S. , Shore, A. , Rediger, K. , Abbatt, J. , Garofalo, L. , Farmer, D. and Poppendieck, D. (2023), Mechanical Ventilation in a Residential Building Brings Outdoor NOx Indoors with Limited Implications for VOC Oxidation from NO3 Radicals, Environmental Science and Technology, [online],, (Accessed April 15, 2024)
Created October 10, 2023, Updated February 14, 2024