Brad Prezant, Affil.AIRAH

Prezant Environmental

Use of SF6 tracer gas to establish air exchange and set a performance baseline for new construction

SF6 has long been employed to measure air exchange, typically in mechanically ventilated buildings. It can be used in occupied or non-occupied buildings, providing advantages to other tracers that cannot be used in occupied buildings due to interference, such as CO2.  While engineering estimates of airflow and air exchange based on either theoretical or measured airflows can provide a rough indication of air exchange, local effects such as thermal currents, diffuser placement, and other factors that influence the efficiency of air exchange often render such estimates inaccurate. This is particularly true for non-turbulent mixing air delivery, such as displacement ventilation. Other technologies, such as blower door testing, are performed in artificial conditions and therefore do not provide information on air exchange under normal conditions. Good estimates of air changes per hour (ACH) are necessary for understanding air quality, and for example, calculating risk of infection due to airborne coronavirus or influenza. 

When air exchange (in ACH) is calculated for a new building, repeat comparative measurements over the following years can provide an efficient overall performance indicator of many mechanical components that can change calibration, age, or otherwise vary in their intended operation.  When problems are identified, further investigation can then be undertaken to determine the reason for substandard performance.  

With a greater emphasis on air quality, performance measures can provide excellent risk communication and assist in keeping occupants satisfied and productive. 


About Brad Prezant:
Brad Prezant is a public health and occupational health scientist, with an epidemiology and public health focus and perspective. He works primarily as a consultant, with additional experience as a university-based research scientist. Over many decades, Brad has served as an independent expert/expert witness in Australia, New Zealand, and the US.

Brad holds a degree in Public and Environmental Health (MSPH) with a focus on occupational health and epidemiology, from the University of Washington School of Public & Environmental Health, and an MBA from the University of Washington School of Business. He served as Affiliate Associate Professor at the UW School of Public Health for 15 years.

He is a Certified Occupational Hygienist (COH, CIH, sub-specialty Indoor Environmental Quality), Certified Air Quality Professional (CAQP), and previously a Certified Professional Ergonomist (CPE). Brad is the current Vice-President of the International Society of Indoor Air Quality & Climate (ISIAQ). He is also an accredited WELL Building professional.

Brad is the Chief Editor of Recognition, Evaluation & Control of Indoor Mold, 2007, AIHA, now in its second edition, and has published technical articles and spoken extensively at industry and professional society conferences.

In the past two years, Brad’s work has focused on assessing and remediating buildings for minimising infection risk from COVID-19 and other disease. With Professor Lidia Morawska, he co-chaired a workshop at Health Buildings Norway presenting a variety of COVID-19 infection risk models, including one he developed to assist building owners/managers.

Brad directed a team of academic scientists, professional engineers, and mechanical contractors on behalf of Coronavirus Quarantine Victoria (CQV) to assess and remediate Victorian hotels early in 2021, before the re-opening of the hotel quarantine program.