May 20, 2020
Transmission of SARS-CoV-2 through the air is sufficiently likely that airborne exposure to the virus should be controlled
On May 7, 2020, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) issued new guidance to assist building owners and decision-makers on how best to reopen their facilities following a closure due to the COVID-19 pandemic. The guidance provides practical information and step-by-step checklists for evaluating the operation of a building's HVAC system and recommends strategies for mitigating the spread of infectious aerosols through air ducts. While specifically focused on preparing a building for reopening, the guide also addresses practical methods for operating a building during the pandemic, outlining occupancy-specific recommendations for commercial buildings and educational facilities. Alterations to building operations suggested in this ASHRAE guidance may require a detailed analysis of the building's current and modified HVAC system. Other related issues may need to be addressed as these assessments are undertaken.
Specific key recommendations include the following:
- Gather a team of professionals that can perform the analysis, testing, design, construction, controls, balancing, commissioning, maintenance, and operation services necessary to evaluate and modify the required systems to meet your specific hazard mitigation strategy.
- Evaluate the building's mechanical system to ensure it is in proper-working order and capable of being modified to align with any HVAC-related mitigation strategy. Specific mitigation strategies may include:
- Increasing the amount of outside air ventilation provided to the building to reduce the amount of air recirculated in the facility. Consideration should be given to the system's ability to maintain the temperature and humidity set points in the space, which not only impacts comfort but the bio-burden of infectious particles in the space.
- Upgrading and improving the efficiency of the filters serving the HVAC system, preferably to a MERV 14 or better. Consideration should be given to the increased airflow resistance generated with higher-efficiency filters and the impact on the performance of fans.
- Before re-occupancy, flush the building by opening up the outside air intake dampers to their maximum position for at least four hours.
Operate the HVAC system in "Occupied" mode for at least 24 hours after flushing the building to ensure proper sequencing, temperature control, and humidity control of the building.
- Continue to perform scheduled maintenance on boilers, chillers, air-handlers, and other mechanical equipment if it may be performed safely.
How Exponent Can Help
Exponent's team of structural and systems engineers can assist in evaluating the performance of your building's HVAC system before reopening and assessing strategies to mitigate the spread of infectious aerosols through air ducts. For companies that operate multiple facilities, Exponent can help streamline the process of implementing ASHRAE's recommendations in multiple buildings, and if a building assessment uncovers additional system complications, Exponent can provide custom analysis.