In addition to our repairs of more than 12,000 windows to support airflow and increase ventilation, BPS installed indoor air quality sensors in all school buildings, beginning with classrooms and learning spaces. Every classroom and common space has an air purifier. Filters have been replaced in all 5,000 air purifiers that were deployed to schools last year. Air purifier filters will be replaced every six months. For our schools with HVAC systems, MERV-13 filters were replaced in accordance with regular building system maintenance.