Conference Agenda

The COVID-19 pandemic has led to worldwide consensus on the importance of indoor aerosol transmission for disease spread. To better prepare for the next infectious disease outbreak, ASHRAE published Standard 241 “Control of Infectious Aerosols”, which is the first-of-its-kind indoor air quality (IAQ) resilience standard that sets requirements for the equivalent clean air delivered to building occupants to control infectious aerosols. For a wide adoption of this new standard, case studies are needed to provide guidance on applying the standard to real buildings. We demonstrated this standard on two office buildings in a mixed humid climate. The two buildings vary in vintage, usage type (single vs. mixed use), HVAC systems, and ventilation/air cleaning methods. We calculated the equivalent clean airflow rates as currently provided by the buildings, compared them with the requirements in the standard, and proposed interventions to meet the standard. We found that the results are more reasonable by investigating rooms or zones that are grouped by HVAC systems and ventilation/air cleaning methods within a building compared to treating the building as a whole. To comply with the standard during the infection risk management mode (IRMM), reducing occupancy is the first step to try, and then a combination of additional interventions (such as increased filtration and natural ventilation) may be required depending on the building.

ASHRAE Standard 241, Control of Infectious Aerosols, was published in 2023 as a response to the COVID pandemic and in recognition of the important role that buildings play in disease transmission. Increasingly, leaders, building experts, and public health officials have come to appreciate that buildings present an opportunity to mitigate disease transmission and make occupants safer and healthier. ASHRAE 241 was a major step forward and is the first code-enforceable indoor air quality standard designed to reduce disease risk. The standard establishes minimum requirements for control of infectious aerosols and was developed by an unprecedented team of interdisciplinary experts, including experts from public health and medical fields.

This standard is an innovative new tool in the public health toolkit, as it an operational standard with an “infection risk management mode” (IRMM), which can be activated as determined by public health officials. What is the role of the public health community in utilizing this new standard or shaping public health practice to include building ventilation? In this work, we outline a framework for implementing standard 241 and its role in the public health toolkit, especially during periods of high respiratory disease. From the Brown University School of Public Health, we will convene public health officials, epidemiologists, physicians, and others to develop an implementation framework. We outline when and how public health officials might use a tool like standard 241 and what data can trigger IRMM (such as emergency department visits or wastewater surveillance). Health-based indoor air quality standards have an important role to play in improving our health, and an important first step is forging connections between engineers and public health officials.

The U.S. General Services Administration (GSA) is committed to lead by example in the design and operation of ventilation systems to promote occupant health and productivity in a post-COVID environment. ASHRAE recently released Standard 241: Control of Infectious Aerosols to reduce the risk of disease transmission in buildings during infection risk management mode (IRMM) with effective clean air strategies. Applying this standard to the large portfolio of existing GSA buildings and new construction would require robust engineering evaluation, consideration of cost and energy impacts, and engagement with building occupants and staff.

GSA developed a plan to pilot ASHRAE Standard 241 following a convening of over 30 experts in the fields of ventilation design, indoor air quality (IAQ), facility management, and public health. The purpose of the pilot study is to explore the optimal approach, costs and level of effort, and potential benefits associated with implementing ASHRAE 241’s equivalent clean air requirements for IRMM. This research investigates how existing data, and some additional low-effort indoor air quality (IAQ) data, could be leveraged to support this effort.

This paper provides results of a baseline assessment for the first study site: a federal courthouse in the Southwest United States. The research leverages existing data to give rough order-of-magnitude ventilation rates and equivalent clean airflows as a preliminary step for comparison with ASHRAE 241 requirements, and it gives an alternative estimation of ventilation performance using steady state CO2 calculations. The assessment found that the quality of available data is not good enough for determining ASHRAE 241 compliance but could be used as a scalable method for triaging GSA buildings that are in greatest need of testing and balancing and the approximate gap to compliance with ASHRAE 241.