April 13, 2023

Many School Districts Have Not Implemented COVID-19 Ventilation Controls, CDC Finds

Results of a survey assessing COVID-19 prevention policies suggest that many U.S. public school districts have failed to implement ventilation improvement strategies, according to CDC’s April 7 Morbidity and Mortality Weekly Report (MMWR). Conducted between August and December 2022, the survey obtained responses from 8,410 kindergarten through grade 12 public school districts, representing 64.2 percent of public school districts and 61.7 percent of enrolled public school students nationwide. Just over half, or 50.7 percent, of school districts reported that they had maintained continuous airflow through school buildings during active hours. For the other strategies assessed in the survey, 33.9 percent of school districts reported replacing or upgrading heating, ventilation, and air conditioning (HVAC) systems; 28.0 percent reported installing or using in-room air cleaners with high-efficiency particulate air (HEPA) filters; and 8.2 percent reported installing ultraviolet germicidal irradiation (UVGI) devices.

Use of each strategy varied by U.S. Census Bureau region. School districts in the West more frequently reported implementing continuous airflow, HVAC system improvements, and air cleaners with HEPA filters compared to schools in the Northeast, Midwest, and South. School districts located in cities more frequently reported using HEPA-filtered air cleaners than districts in suburban, town, and rural areas. Use of UVGI devices was the least common strategy overall but was reported slightly more often among school districts in the South and in rural areas.

Overall, school districts preferred implementing less costly strategies, according to the report. School districts in the West may have been better able to replace or upgrade HVAC systems because their schools are generally newer than those in other regions. Rural schools may have been more likely to use natural ventilation due to concerns with air quality and noise in urban areas.

High-poverty school districts reported using each of the four ventilation strategies more often than low- and mid-poverty school districts. A previous CDC report indicated that high-poverty school districts may have more experience applying for federal funding to make ventilation improvements.

The report cautions that the survey had a high proportion of “unknown” or missing responses, possibly because the administrative staff who responded to the survey may have had limited awareness of ventilation strategies used within their district. Therefore, implemented ventilation improvements were likely underreported. The survey also did not examine school-level ventilation improvements within districts, and schools may have implemented ventilation strategies other than the four assessed by the survey.

The survey’s findings highlight “the ongoing opportunity to improve indoor air quality among K–12 school buildings in the United States,” the MMWR states. More information is available in the full report.