The Chemical Assessment of Surfaces and Air (CASA) Study: Using chemical and physical perturbations in a test house to investigate indoor processes

Published

June 21, 2024

Author(s)

Delphine K Farmer, Marina E Vance, Dustin Poppendieck, Jon Abbatt, Michael R Alves, Karen C Dannemiller, Cholaphan Deeleepojananan, Jenna Ditto, Brian P. Dougherty, Olivia R Farinas, Allen H Goldstein, Vicki H Grassian, Han Huynh, Deborah Kim, Jon C King, Jesse Kroll, Jienan Li, Michael Link, Liora Mael, Kathryn Mayer, Andrew B Martin, Glenn Morrison, Rachel O’Brien, Shubhransgshu Pandit, Barbara Turpin, Marc Webb, Jie Yu, Stephen Zimmerman

Abstract

The Chemical Assessment of Surfaces and Air (CASA) study aimed to understand how chemicals transform in the indoor environment using perturbations (e.g., cooking, cleaning) or additions of indoor and outdoor pollutants in a well-controlled test house. Chemical additions ranged from individual compounds (e.g., addition of gaseous ammonia or ozone) to more complex mixtures (e.g., a wildfire smoke proxy and a commercial pesticide product). Physical perturbations included varying temperature, ventilation rates, and relative humidity (RH). The objectives for CASA included understanding (i) how outdoor air pollution impacts indoor air chemistry, (i) how wildfire smoke transports and transforms indoors, (iii) how gases and particles interact with building surfaces, and (iv) how indoor environmental conditions impact indoor chemistry. Further, the combined measurements under unperturbed and experimental conditions enable investigation of mitigation strategies following outdoor and indoor air pollution events. A comprehensive suite of instruments measured different chemical components in the gas, particle, and surface phases throughout the study. We provide an overview of the test house, instrumentation, experimental design, and initial observations – including the role of humidity in controlling the air concentrations of many semi-volatile organic compounds, the potential for ozone to generate indoor nitrogen pentoxide (N2O5), the differences in microbial composition between the test house and other occupied buildings, and the complexity of deposited particles and gases on different indoor surfaces.

Citation

Environmental Science: Processes and Impacts

Pub Type

Journals

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Citation

Farmer, D. , Vance, M. , Poppendieck, D. , Abbatt, J. , Alves, M. , Dannemiller, K. , Deeleepojananan, C. , Ditto, J. , Dougherty, B. , Farinas, O. , Goldstein, A. , Grassian, V. , Huynh, H. , Kim, D. , King, J. , Kroll, J. , Li, J. , Link, M. , Mael, L. , Mayer, K. , Martin, A. , Morrison, G. , O’Brien, R. , Pandit, S. , Turpin, B. , Webb, M. , Yu, J. and Zimmerman, S. (2024), The Chemical Assessment of Surfaces and Air (CASA) Study: Using chemical and physical perturbations in a test house to investigate indoor processes, Environmental Science: Processes and Impacts, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=957915 (Accessed October 6, 2025)