ASHRAE Recommendations for Reducing Airborne Infectious Aerosol Exposure

American Society of Heating Refrigerating and Air-Conditioning Engineers Logo

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Epidemic Task Force has provided continuous research and recommendations for building owners, occupants, and design professionals throughout the evolution of the COVID-19 pandemic.
These recommendations vary by building occupancy and existing mechanical systems. In an effort to clarify the most important and universally applicable recommendation, ASHRAE has released a document titled “Core Recommendations for Reducing Airborne Infectious Aerosol Exposure.”

This document is available HERE and reproduced below for reference:

1. Public Health Guidance

  • Follow all regulatory and statutory requirements and recommendations for social distancing, wearing of masks and other PPE, administrative measures, circulation of occupants, reduced occupancy, hygiene, and sanitation.

2. Ventilation, Filtration, Air Cleaning

  • Provide and maintain at least required minimum outdoor airflow rates for ventilation as specified by applicable codes and standards.
  • Use combinations of filters and air cleaners that achieve MERV 13 or better levels of performance for air recirculated by HVAC systems.
  • Only use air cleaners for which evidence of effectiveness and safety is clear.
  • Select control options, including standalone filters and air cleaners, that provide desired exposure reduction while minimizing associate energy penalties.

3. Air Distribution

  • Where directional airflow is not specifically required, or not recommended as the result of a risk assessment, promote mixing of space air without causing strong air currents that increase direct transmission from person-to-person.

4. HVAC System Operation

  • Maintain temperature and humidity design setpoints.
  • Maintain equivalent clean air supply required for design occupancy whenever anyone is present in the space served by a system.
  • When necessary to flush spaces between occupied periods, operate systems for a time required to achieve three air changes of equivalent clean air supply.
  • Limit re-entry of contaminated air that may re-enter the building from energy recovery devices, outside air intakes, and other sources to acceptable levels.

5. System Commissioning

  • Verify that HVAC systems are functioning as designed.

Disclaimer: The COVID-19 pandemic is a situation that is evolving every day. The information here is based on the recommendations provided by the Centers for Disease Control and Prevention (CDC), Environmental Protection Agency (EPA), and American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). Please refer to these agencies for the latest information.