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01/14/2021

ASHRAE: Recommendations for reducing airborne infectious aerosol exposure

Marianne Wilson
Editor-in-Chief
Marianne Wilson profile picture

The ASHRAE Epidemic Task Force has released new guidance to address the control of airborne infectious aerosol exposure.

An infectious aerosol is a suspension in air of fine particles or droplets containing pathogens such as the SARS-CoV-2 virus that can cause infections when inhaled. They can be produced by breathing, talking, sneezing and other ways as well.
 
ASHRAE’s Core Recommendations for Reducing Airborne Infectious Aerosol Exposure summarize the main points found in the detailed guidance documents produced by the ASHRAE Epidemic Task Force. They are based on the concept that ventilation, filtration and air cleaners can be combined flexibly to achieve exposure reduction goals subject to constraints that may include comfort, energy use and costs.

“This guidance outlines a clear approach for lessening the risk of infectious aerosol exposure for building occupants that can be applied in a wide range of applications,” said William Bahnfleth, ASHRAE Epidemic Task Force chair. “ASHRAE’s Core Recommendations are based on an equivalent clean air supply approach that allows the effects of filters, air cleaners, and other removal mechanisms to be added together to achieve an exposure reduction target.”

Specific recommendations include the following:
•    Public Health Guidance
o    Follow all regulatory and statutory requirements and recommendations.

•    Ventilation, Filtration, Air Cleaning
o    Outdoor airflow rates guidance for ventilation as specified by applicable codes and standards.
o    Recommendations on filters and air cleaners that achieve MERV 13 or better levels of performance.
o    Air cleaners usage.
o    Control options that provide desired exposure reduction while minimizing associated energy penalties.
o    Air Distribution
o    Promote the mixing of space air.

•    HVAC System Operation
o    Maintain temperature and humidity design set points.
o    Maintain equivalent clean air supply required for design occupancy.
o    Operate systems for a time required to achieve three air changes of equivalent clean air supply.
o    Limit re-entry of contaminated air.

•    System Commissioning
o    Verify that HVAC systems are functioning as designed.

To view the complete ASHRAE Core Recommendations For Reducing Airborne Infectious Aerosol Exposure, visit ashrae.org/COVID-19.