According to the group, an infectious aerosol is a suspension in air of fine particles or droplets containing pathogens such as the SARS-CoV-2 coronavirus that causes Covid-19, that can cause infections when inhaled. The particles can be produced by breathing, talking and sneezing as well as by flushing toilets and by certain medical and dental procedures.
ASHRAE’s Core Recommendations for Reducing Airborne Infectious Aerosol Exposure concisely 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.
William Bahnfleth, ASHRAE Epidemic Task Force chair, explained:
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, from homes to offices to mobile environments such as vehicles and ships. 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
- Follow all regulatory and statutory requirements and recommendations.
- Ventilation, Filtration, Air Cleaning
- Outdoor airflow rates guidance for ventilation as specified by applicable codes and standards
- Recommendations on filters and air cleaners that achieve MERV 13 or better levels of performance
- Air cleaners usage
- Control options that provide desired exposure reduction while minimizing associated energy penalties
- Air Distribution
- Promote the mixing of space air.
- HVAC System Operation
- Maintain temperature and humidity design set points.
- Maintain equivalent clean air supply required for design occupancy.
- Operate systems for a time required to achieve three air changes of equivalent clean air supply.
- Limit re-entry of contaminated air.
- System Commissioning
- Verify that HVAC systems are functioning as designed.
To view the complete Core Recommendations for Reducing Airborne Infectious Aerosol Exposure Resources and other Covid-19 Resources, visit the ASHRAE website.