About

William Bahnfleth is a Professor in the Department of Architectural Engineering at Penn State University. His research focuses on building mechanical systems, including HVAC, chilled water systems, thermal storage, and indoor air quality. He has contributed extensively to understanding and improving indoor environmental quality, particularly in relation to human health and productivity, and has authored works on protecting building occupants from biological and chemical airborne threats. His expertise also encompasses modeling, simulation, and diagnostics under uncertainty, as well as automation, robotics, and digital twins in construction. Bahnfleth holds a BS, MS, and PhD in Mechanical Engineering from the University of Illinois at Urbana-Champaign and has authored numerous publications, including books and journal articles, on indoor chemistry, air quality, and infection control in built environments.

Research topics

• Internal medicine
• Medicine
• Mathematics education
• Physics
• Intensive care medicine
• Developmental psychology
• Virology
• Psychology

Selected publications

• Lüften sounds simple – but ‘house-burping’ is more complicated in Pittsburgh

  2026-02-04

  article1st authorCorresponding
  PublisherDOI

• Breaking Down Silos: A Multidisciplinary Approach to Mitigate Indoor Airborne Pathogen Transmission

  Health Security · 2026-02-01 · 1 citations

  articleOpen access

  Addressing indoor air quality (IAQ) is essential for reducing respiratory disease risks. In this commentary, we highlight the need for increased connections between typically siloed engineering and health disciplines to tackle remaining IAQ knowledge gaps that, if closed, would enhance IAQ applications and health. We provide actionable insights for policymakers, building designers, and funding agencies, recommending multidisciplinary research to support (1) increasing understanding of the complex and multifactorial variables in human infection, (2) using physical and mathematical models to understand disease transmission, and (3) determining the effectiveness of layered interventions in different environments. Addressing these knowledge gaps will help in the delivery of cost-effective IAQ solutions that reduce infectious disease risks in workplaces, schools, homes, and other indoor environments.

  PublisherOA PDFDOI

• An indoor air pollution research strategy for the United Arab Emirates

  Indoor Environments · 2025-03-23 · 1 citations

  articleOpen access

  Clean indoor air is vital for health in all settings, especially in locations where extreme climates restrict outdoor activity, such as in the United Arab Emirates (UAE). UAE summer temperatures routinely exceed 42°C (108°F), discouraging outdoor activity and limiting natural ventilation of structures. Yet, little research is available on indoor air quality in the UAE. To inform the design of a new indoor air quality program, the Abu Dhabi Public Health Centre commissioned a study to characterize and prioritize knowledge gaps on indoor air quality and its relationship to health in the UAE and to identify potential partners for the program. Research gaps and priorities were identified by a panel of 16 international and local indoor air quality experts through a two-day structured, in-person workshop and follow-up survey. Key partners were identified through a stakeholder mapping exercise and e-mail survey of 79 government agencies and nongovernment organizations. The expert panel concluded that the most important short-term research need is to characterize the major sources of indoor air pollution and the most frequently occurring pollutants. The panel recommended establishing a national indoor air quality observatory encompassing a wide range of settings, including residences, schools, mosques, healthcare facilities, shopping malls, and other public spaces. Indoor air quality monitors would be permanently placed to establish baseline indoor air quality, provide data to estimate source contributions, and enable tracking of changes over time. The stakeholder mapping exercise identified ten agencies that should be involved in planning, including the Abu Dhabi Public Health Centre, Department of Health–Abu Dhabi, Environment Agency–Abu Dhabi, Abu Dhabi Department of Energy, and Emirates Public Health Association. While focused on the UAE, the methods and research priorities in this study may be useful for planning indoor air quality improvement campaigns in other high-income nations.

  PublisherDOI

• Three things we can do now to reduce the risk of avian influenza spillovers

  Proceedings of the National Academy of Sciences · 2025-07-30 · 1 citations

  articleOpen access
  PublisherOA PDFDOI

• Analysis of indoor secondary organic aerosol formation near occupants in a classroom using computational fluid dynamics simulations

  Environmental Science Processes & Impacts · 2025-01-01

  articleOpen access

  Secondary organic aerosol (SOA) forms indoors when ozone reacts with terpenes, generating a range of low- and semi-volatile compounds, over 50% of which partition into the particle phase. This study investigated the formation of SOA in indoor spaces under heterogeneous thermal conditions resulting from the combined effects of HVAC systems and heat emitted by human occupants. The core of this study involved integrating the volatility basis set (VBS) model with computational fluid dynamics (CFD) simulations. The resulting VBS-CFD framework was used to simulate SOA formation from ozone-terpene reactions, with terpenes originating from human emissions. Model accuracy was assessed using experimental data from previous measurement studies and a material balance model. Results indicate that semi-volatile compound concentrations are substantially higher near occupants compared to ambient levels, while SOA concentrations are lower near humans due to temperature gradients. The study results further revealed notable spatial variability in SOA concentrations under both cooling and heating scenarios, despite maintaining a consistent average indoor temperature. These findings highlight the important role of semi-volatile compounds in influencing particle concentrations near occupants, with over 50% of these compounds potentially contributing to aerosol formation-and thereby increasing human exposure to indoor aerosols.

  PublisherOA PDFDOI

• Author response for "Analysis of indoor secondary organic aerosol formation near occupants in a classroom using computational fluid dynamics simulations"

  2025-07-08

  peer-review
  PublisherDOI

• AI as a Catalyst for Synergistic Gains in Indoor Air Quality and Energy Efficiency

  SSRN Electronic Journal · 2025-01-01

  preprintOpen access
  PublisherDOI

• Author response for "Analysis of indoor secondary organic aerosol formation near occupants in a classroom using computational fluid dynamics simulations"

  2025-06-21

  peer-review
  PublisherDOI

• Engineering Infection Controls to Reduce Indoor Transmission of Respiratory Infections

  Annals of Internal Medicine · 2025-08-04 · 3 citations

  review

  BACKGROUND: Engineering infection controls include a wide range of interventions used indoors to reduce occupants' exposure to respiratory pathogens. PURPOSE: To identify and describe primary studies evaluating the effects of engineering infection control interventions designed to reduce the spread of respiratory infections transmitted through indoor air. DATA SOURCES: MEDLINE, Embase, Global Health, Cochrane Central Register of Controlled Trials, CINAHL, Scopus, and Environmental Science Collection from database inception to 12 December 2023. STUDY SELECTION: English-language primary research articles evaluating engineering infection control interventions. DATA EXTRACTION: Publication information, population characteristics, intervention details, and all relevant outcomes were abstracted by a reviewer and verified by a second, senior reviewer. DATA SYNTHESIS: = 149). Harms, such as toxic byproducts, were rarely measured. LIMITATION: Exclusion of non-English-language publications and gray literature. CONCLUSION: There is substantial heterogeneity in the available evidence. Gaps in evidence include studies measuring efficacy outcomes that are highly relevant for human infection transmission or harms. Refinements in classification of interventions and outcomes could strengthen reporting of these evaluations. PRIMARY FUNDING SOURCE: National Institute for Occupational Safety and Health at the Centers for Disease Control and Prevention. (Registered on Open Science Framework [https://osf.io/5zmhd]).

  PublisherDOI

• Policy and Regulatory Roadmap to Achieve Health-Based Indoor Air Quality Standards

  2025-11-05

  article1st authorCorresponding
  PublisherDOI

Frequent coauthors

• James D. Freihaut

  33 shared

• Władysław Kowalski

  18 shared

• Brandolyn H. Thran

  United States Army

  18 shared

• Amy Musser

  University of Maryland, College Park

  15 shared

• Chandra Sekhar

  National University of Singapore

  14 shared

• Stephanie J. Dancer

  14 shared

• Jae‐Weon Jeong

  Hanyang University

  13 shared

• Richard G. Mistrick

  13 shared

Education

• PhD, Mechanical Engineering

  University of Illinois

  1989

• BMus (performance), Music

  University of Illinois

  1988

• MS, Mechanical Engineering

  University of Illinois

  1980

• BS, Mechanical Engineering

  University of Illinois

  1979

Awards & honors

• Outstanding Engineering Alumni Award
• ASAE Early Career Impact Award
• Penn State Engineering Alumni Society Awards
• Penn State Alumni Association Awards