Ventilation in AAPS Buildings

  • AAPS lead, care, inspire graphicVentilation in AAPS Buildings 
    Wednesday, August 25, 2021
    Emile Lauzzana, Executive Director, Capital Projects

    AAPS has received several communications recently regarding ventilation in AAPS schools.  The health and safety of our students and staff are a top priority at AAPS. 

    The District recognized early in the pandemic that ventilation was a critical part of a layered risk mitigation strategy. We have been working with consulting engineers since April of 2020 to improve our Heating, Ventilating and Air Conditioning (HVAC) systems across all 35 AAPS buildings,1,000 classrooms, and 3,500,000 square feet. These improvements have included:

    • Commissioning and deep cleaning of all ventilation equipment
    • Developing a new Enhanced Indoor Air Quality (EIAQ) mode of operation for the HVAC systems that maximizes the rate of ventilation well beyond the normal operating mode
    • Increasing the efficacy of the district air filters and increasing the replacement frequency to three times per year
    • Conducted a study of each building measuring the effective Air Changes per Hour (ACH) in occupied spaces.   The study results are posted on the District's website here:
    • Installing portable air cleaners in spaces that fall below the recommended 5 ACH level.

    These actions have been presented publicly to the Board of Education on several occasions and are captured here in video format:

    The scientific community has been working at a record-breaking pace since the beginning of the COVID-19 pandemic on a wide range of solutions. We appreciate all of the expertise in our community offering their assistance in helping mitigate the risk of transmission in our school buildings and throughout our Ann Arbor community.

    Regarding the specific requests the District has received recently, AAPS can provide the following clarifications and responses:

    1. Opening of Windows - AAPS absolutely supports opening windows whenever possible.  The District also recognizes there are buildings in the District that do not have operable windows or times of the year where the outdoor temperature is extreme and prevents the opening of windows.  In part because of these conditions, the detailed ACH study was conducted to ensure that even in rooms without operable windows, or at times when outside temperatures prevent the opening of windows, a minimum of 5 ACH is feasible throughout the District.

    2. Portable Air Cleaners - The District has researched and tested several models of portable air cleaners.  While some of the smaller residential air cleaners are relatively quiet, the larger units (300 CADR+) that can have a significant positive impact on indoor air quality in a classroom-sized space are quite loud.  Product literature and District testing found levels of 59-68 dB when operating the fan on the high mode.  This level of noise is significant and raises concerns regarding classroom efficacy and disruptions.  The District has deployed a number of Austin Air/Goodyear portable air cleaners to spaces that fall below the 5 ACH threshold.  This unit was found to have one of the lower noise levels at 61dB, a solid construction, to be reasonably priced (~$500/unit), readily available and have a long-lasting HEPA filter.

      The District is not opposed to parents or others purchasing portable air cleaners for schools. However, the specific make, model and quantity must be approved by the school district prior to installation.  The District is working to create a pre-approved list of portable air cleaners to share with the community.

    3. Filter/Corsi Cubes - These DIY projects involve the use of glue and duct tape to attach a HEPA filter directly to a standard box fan.  These devices are a modification to an Underwriter's Laboratory (UL) listed item UL 507 - Standard for Electric Fans.  While the recently released July 2021 study ( content/uploads/DIY-Box-Fan-Report-2021.pdf) helps to move forward the conversation regarding this DIY solution, the authors of the study are careful to note the following in their publication:

      This research study was conducted on a limited number of fans readily available in the marketplace, and results may not be representative of all available. Research results do not imply that the fans or fans with filters used in this study and with the described filter conditions meet UL 507; that can only be confirmed with compliant safety testing requirements and third-party verifications.

      The District cannot support the use of these DIY solutions as there are unknown fire and other risks associated with unapproved modifications to UL-listed equipment.

      Additional concerns include the potential for the release of particulates should the filter be kicked or the fans fall to the floor (typical air clearer have the filter protected by a housing); the potential for particulate release due to backdraft as the fans are shut down or in an idle position; maintenance and how and when the glued and taped filter be changed and by whom; how many would be required, their efficacy and where they should be placed; and generally how to calculate the efficacy of a DIY solution in conjunction with other mitigation strategies such as the ventilation and filtration provided by each building’s HVAC system.

    4. CO2 Sensors - CO2 sensors measure the level of CO2 in a room and are one of many indicators of indoor air quality.  Additional indicators include but are not limited to particulates, volatile organic compounds, mold, carbon monoxide, radon, and others. Professional grade sensors begin at about $200-300 each.  The District is not aware of reliable sensors at a lower cost.  There is also concern regarding false positives or negatives as lower-cost items may be inaccurate.  The District will continue to research the potential of these sensors and how they could effectively support a layered risk management strategy.

    5. Needlepoint Bipolar Ionization - There is some concern that the optional needlepoint bi-polar ionization included in the new window AC units the District is installing may generate dangerous ozone, volatile organic compounds, or other by-products that carry health concerns.  While earlier versions of this technology were found to produce these unwanted by-products, the District specifically selected next-generation technology, in conjunction with consulting engineers, that has been tested to not produce either ozone or VOCs.  Some of these tests are included at this link and include both manufacturer and customer conducted tests:  Air Ionization Case Studies & Research (  The units are also UL Listed and ANSI certified to not produce ozone.

    6. Recognizing that this is newer technology, and out of an abundance of caution, the District is exploring how to independently verify the safety of this equipment through additional testing, similar to the customer testing conducted in the case studies cited above. In the event the devices are found to produce harmful by-products, this optional equipment can easily be disconnected and removed from the equipment.