OSU’s COVID-19 Safety & Success plan demonstrates the important measures Oregon State is taking to reduce the spread of COVID-19. Current data suggest1 that the coronavirus spreads mostly through inhaled respiratory droplets produced by breathing, coughing and sneezing.
Physical distancing, face coverings and enhanced cleaning measures help reduce the spread of COVID-19. However, as research shows, the virus can be present in uncirculated air for hours, so OSU Facilities Services has taken steps to reduce risk by reviewing and adjusting building ventilation systems on the Corvallis and Bend campuses. These steps align with OSHA guidance to improve ventilation, published in January 2021.
Building ventilation is most often controlled through the building’s heating, ventilation and air conditioning systems (HVAC) by adding fresh, outside air.
Air Exchange Rate
Air exchange rate is the number of air changes per hour in a particular space in a building that contains mechanical air handlers. The air exchange rates vary depending on the space, but average approximately four changes per hour for offices and six air changes per hour for lab spaces. Classroom air exchange rates typically fall between four and eight air changes per hour, depending on classroom size.
Ventilation and Outside Air
OSU’s building ventilation can be divided into three types:
Recirculated/Mixed Air Systems
Multiple Air System Spaces - usually includes 100% Outside Air Systems as part of a lab space
Many OSU building HVAC systems can be modified to allow for more fresh air and to dilute stagnant air and airborne viruses. To that end, Facilities Services has modified campus HVAC operations following the recommendations of the Centers for Disease Control and Prevention and the American Society of Heating Refrigeration and Air Conditioning Engineers.
Laboratory buildings have ventilation systems with single pass air, meaning there is no recirculation of air from inside the lab space. Office and classroom buildings, by design, recirculate a portion of the air to help conserve energy under normal circumstances, which balances air quality and energy efficiency. Under the current pandemic response, the amount of recirculated air has been decreased as much as possible.
Buildings on the Corvallis and Bend campuses were designed for specific filters recommended by ASHRAE. The function of the space (office, lab, resident hall or classroom) determines the design of the system, which in turn determines the type of filter used.
Facilities Services replaces air filters on schedule, in line with CDC, industry best practices and the system recommendations. More frequent replacement is not recommended by ASHRAE or the CDC, as it has not been shown to appreciably reduce viral spread, but it would potentially increase the risk of exposure for the technicians doing the replacements.
How Facilities Services has worked to improve ventilation and filtration
Consequently, and in keeping with CDC and ASHRAE guidance, Facilities Services staff have taken the following steps to maximize air flow in Corvalis and Bend campus buildings:
Evaluating each building’s HVAC system and determining the appropriate strategy for increasing fresh air.
Increasing filtration where possible.
Adjusting the airflow in office and classroom buildings to maximize fresh air supply.
Using building mechanical exhaust venting as much as possible.
Maximizing ventilation effectiveness by opening windows and doors where practical.
Replacing filtration in HVAC systems as scheduled.