The key to opening schools: Better air flow

Where it stands: 4 in 10 U.S. school districts need to update or replace the HVAC systems in at least half of their school buildings — affecting about 36,000 school buildings, according to a June 2020 Government Accountability Office report.

At a school in Rhode Island, some components of its HVAC system are nearly 100 years old. A Michigan school is heating the building using a boiler from the 1920s, per the report.

Some school buildings that remained open this year tried to increase air flow by opening windows to incorporate outside air and used fans to keep air circulating. This is hard to do on very hot or cold days, though.