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.

“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,” 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
  • 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; and 
  • 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; and
  • Limit re-entry of contaminated air.
     
• System Commissioning
  • Verify that HVAC systems are functioning as designed.

The task force’s Communities of Faith Buildings guidance offers recommendations on conducting worship services under epidemic conditions. 

“The intent of the Communities of Faith guidance is to offer those who operate and care for buildings used for worship a plan for implementing short- and long-term HVAC strategies to reduce the possibilities of transmission of the SARS-CoV2-2 virus,” said Rick Karg, member, ASHRAE Epidemic Task Force. “The document also helps communities move toward a new 'normal' operation after this public health emergency nears an end.” 

Recommendations for Communities of Faith include the following:

• Identify HVAC system characteristics. Compile and review operation and maintenance manuals and schedules.
   
• Verify HVAC systems are well maintained and operating as intended. For maintenance, follow the requirements of ASHRAE Standard 180 - 2018, “Standard Practice for the Inspection and Maintenance of Commercial HVAC Systems.”
  • Consider PPE when maintaining HVAC systems including filters, coils, and drain pans.
     
• Operate HVAC systems, if present, with system fan set to run continuously when building is occupied for services or cleaning.
   
• Operate the system for a time required to achieve three equivalent air changes of outdoor air (effect of outdoor air, filtration and air cleaners) before the first daily occupancy and between occupied periods, if appropriate. Three equivalent air changes can be calculated using ASHRAE’s Building Readiness Guide.

To view the complete ASHRAE Core Recommendations For Reducing Airborne Infectious Aerosol Exposure and Communities of Faith Building guidance, visit ashrae.org/COVID-19.