ASHRAE approves infectious aerosol control standard

ASHRAE has announced the approval for publication of its airborne infection risk mitigation standard for buildings.

ASHRAE Standard 241 Control of Infectious Aerosols establishes minimum requirements to reduce the risk of disease transmission by exposure to infectious aerosols in new buildings, existing buildings, and major renovations. The standard has been developed to reduce exposure to SARS-COV-2 virus, which causes COVID-19, influenza viruses and other pathogens that cause major personal and economic damage every year. Standard 241 provides requirements for many aspects of air system design, installation, operation, and maintenance.

Important aspects of the standard include:

Infection Risk Management Mode (IRMM)

This mode applies during identified periods of elevated risk of disease transmission. Authorities can determine when enhanced protection is required, but its use can also be at the discretion of the building owner or operator at other times, for example, during influenza season. This aspect of Standard 241 introduces the concept of resilience – ability to respond to extreme circumstances outside normal conditions – into the realm of indoor air quality control design and operation.

Requirements for equivalent clean airflow rate

Other indoor air quality standards, including ASHRAE Standards 62.1, 62.2, specify outdoor airflow rate and filtration requirements to control normal indoor air contaminants. Standard 241 sets requirements for equivalent clean airflow rate, the flow rate of pathogen-free air flowing into occupied areas of a building that would have the same effect as the total of outdoor air, filtration of indoor air, and air disinfection by technologies such as germicidal ultraviolet light. This approach allows the user of the standard flexibility to select combinations of technologies to comply with the standard that best satisfy their economic constraints and energy use goals.

Requirements for use of filtration and air cleaning technology

ASHRAE notes that dilution of indoor air contaminants by ventilation with outdoor air can be an energy intensive and expensive way to control indoor air quality. Standard 241 provides extensive requirements for use of filtration and air cleaning to meet equivalent clean airflow requirements efficiently and cost effectively. These include testing requirements to establish performance and to demonstrate that operation does not degrade indoor air quality in other ways, for example by elevating ozone levels.

Planning and commissioning

Standard 241 provides assessment and planning requirements culminating in the development of a building readiness plan, a concept carried over from the work of the ASHRAE Epidemic Task Force. It also describes procedures for commissioning systems to determine their installed performance.

“Standard 241 represents a significant step forward in prioritizing indoor air quality,” says ASHRAE President Farooq Mehboob.

“By implementing the requirements outlined in this standard, we can improve the health, wellbeing and productivity of building occupants. This standard empowers building owners, operators and professionals to take proactive measures in safeguarding indoor environments. It’s an essential tool for creating healthier indoor environments and promoting sustainable practices.”

The development of the standard has been notable for its speed  – the consensus process from project approval, development and final approval of the standard, including a public review, took six months from authorisation to completion and only four months of development time dating from the first meeting of the project committee.

“Volunteers and staff dedicated their expertise and thousands of hours of their time to address this urgent industry and societal need,” says ASHRAE Standard Project Committee 241 chair William Bahnfleth.

“The development of this standard shows not only ASHRAE’s ability to respond rapidly to a societal need, but also a steadfast commitment to the health and safety people in buildings everywhere. This is a significant achievement and milestone in connecting building design and operation with public health.”

Although it is not an ANSI standard, there have been calls to take up the approach in Australia.

ASHRAE says the Standard 241 committee will continue improving sections of the standard, adding additional requirements, clarifying requirements and developing tools to help the public use the standard. Industry and consumer-friendly resources such as courses, podcasts, factsheets and information events will be introduced in the future.

Photo by Benjamin Child on Unsplash

One Reply to “ASHRAE approves infectious aerosol control standard

  1. ASHRAE plays a crucial role in setting industry standards for building systems and indoor environmental quality, and it’s likely that they have continued to refine and develop guidelines for mitigating the spread of infectious aerosols in indoor spaces. For the most current and accurate information, I recommend visiting the official ASHRAE website or checking reliable news sources for any updates on this topic.

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