International. The ASHRAE Epidemic Working Group has published new guidance to address the control of exposure to airborne infectious aerosols and recommendations for faith community buildings.
An infectious aerosol is a suspension in the air of fine particles or droplets containing pathogens such as the SARS-CoV-2 virus that can cause infections when inhaled. They can occur when breathing, talking, sneezing, and others, as well as flushing toilets and through certain medical and dental procedures.
ASHRAE's basic recommendations for reducing exposure to airborne infectious aerosols concisely summarize the main points found in the detailed guidance documents produced by the ASHRAE Epidemic Working Group. They are based on the concept that ventilation, filtration and air purifiers can be flexibly combined to achieve exposure reduction goals subject to restrictions that may include comfort, energy use and costs.
"This guidance outlines a clear approach to reducing the risk of exposure to infectious aerosols for building occupants that can be applied in a wide range of applications, from homes to offices and mobile environments such as vehicles and ships," said William Bahnfleth, ASHRAE Epidemic Task Silla Force. "ASHRAE's core recommendations are based on an equivalent clean air supply approach that allows the effects of filters, air purifiers and other disposal mechanisms to add up to achieve an exposure reduction target."
Specific recommendations
- Public Health Guidance
- Follow all regulatory and legal requirements and recommendations.
- Ventilation, filtration, air cleaning
- Orientation of outdoor airflow rates for ventilation as specified by applicable codes and standards.
- Recommendations on air filters and purifiers that reach MERV 13 or better performance levels.
- Use of air cleaners.
- Control options that provide the desired exposure reduction while minimizing the associated energy penalties.
- Air distribution
- Promote space air mixing.
- HVAC System Operation
- Maintain temperature and humidity design set points.
- Maintain the equivalent clean air supply required for design occupancy.
- Operate the systems for as long as necessary to achieve three equivalent clean air supply air changes.
- Limit the re-entry of polluted air.
- Commissioning of the system
- Verify that HVAC systems are working as designed.
The task force's Guide to Faith Community Buildings offers recommendations on how to conduct worship services in epidemic conditions.
"The intent of the Faith Communities orientation is to offer those who operate and care for buildings used for worship a plan to implement short- and long-term HVAC strategies to reduce the chances of transmission of the SARS-CoV2-2 virus. The document also helps communities move towards a new 'normal' operation after this public health emergency comes to an end," said Rick Karg, a member of ASHRAE's Epidemic Working Group.
Recommendations for communities
- Identify the characteristics of the HVAC system. Collect and review manuals and operation and maintenance programs.
- Verify that HVAC systems are well maintained and working as intended. For maintenance, follow the requirements of the standard
- ASHRAE 180-2018, standard practice for the inspection and maintenance of commercial HVAC systems.
- Consider using PPE when maintaining HVAC systems, including filters, coils, and drain trays.
- Operate HVAC systems, if any, with the system fan configured to operate continuously when the building is occupied for services or cleaning.
- Operate the system for the time necessary to achieve three equivalent air changes from outside air (outside air effect, filtration and air filters) before the first daily occupancy and between busy periods, if applicable. Three equivalent air changes can be calculated using the ASHRAE Building Readiness Guide.
For the full ASHRAE core recommendations for reducing exposure to airborne infectious aerosols and the guide to building faith communities, visit ashrae.org/COVID-19.
