Building Ventilation Reports

Minneapolis Public Schools (MPS) completed ventilation studies for all occupied elementary, middle school, high school buildings and central office buildings. These studies identified improvements to the ventilation in our buildings. The basis of the recommended improvements was the guidance provided by the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) to limit virus transmission in the ventilation systems.  

Adequate outdoor air flow, or ventilation, can dilute the number of viral particles in the breathing zone. Effective filtration can remove particles from the air that is recirculated. However, viral particles are extremely small. Most filters are not rated to capture particles as small as the virus that causes COVID-19, but some filters can capture a large fraction of viral-sized particles. While it is not practical to rely only on filtration, increasing filtration levels will reduce the number of viral particles in the air. Increased filtration coupled with maximum outside air provides the best approach to limiting virus transmission through the ventilation system.

The reports provide the results from the reviews conducted by KFI at the request of MPS. The reports recommend improvements to the ventilation systems. MPS evaluated each of the reports and implemented the following improvements to the school ventilation systems.

• Where the existing system filtration could be improved to MERV 14 or higher, Plant Maintenance and Plant Operations changed/upgraded filters. 
• The Building Automation System (BAS) has been reprogrammed to start the ventilation system two hours before staff or students enter the building and will remain operational until two hours after the staff closes the building. This will ensure adequate fresh air is provided to the building.
• Where increased filtration could not be achieved in the existing system, MPS delivered portable HEPA filtration units to each classroom. These units have the capability of filtering two air exchanges per hour through the HEPA filter. This will provide increased filtration of the air to reduce the number of viral particles. 
• The reports identify a potential illness room in each of the schools. The recommendations were reviewed by school staff and each school has a designated illness room that includes a portable HEPA filtration unit.
• The reports also included recommended improvements to the ventilation systems that require capital investment. These improvements are being reviewed by Plant Maintenance for potential future capital investment.
• The reports contained information on ventilation systems as compared to the current code requirements. The code is complex and depends on several factors including the number of people in the room, ambient temperature and room temperature requirements and sizing of the units. Each ventilation system met the code at the time of installation. Changes in code do not require retrofit of ventilation systems until replacement of the systems.

Specific questions regarding the reports should be directed to facilities@mpls.k12.mn.us.

Please see the More Information section to the right to view Building Ventilation Reports for each school site.