SARS-CoV-2 spreads by inhaling infectious particles, so ventilation is one
of the few school measures that works on the mechanism rather than the
behaviour. CDC surveyed US K–12 public school districts by telephone from
August to December 2022 to find out what had actually been done.
What had been done
| Strategy | Districts reporting it in most schools |
|---|---|
| Maintaining continuous airflow during active hours — windows and doors open, fans, thermostat or central control changes | 50.7% |
| Replacing or upgrading HVAC systems | 33.9% |
| In-room air cleaners with HEPA filters | 28.0% |
| Ultraviolet germicidal irradiation (UVGI) devices | 8.2% |
None of the four was reported by more than 51% of districts. The cheapest
one — opening windows and running fans — is the most common, and half the
districts did not report doing it.
The finding that runs the other way
**High-poverty districts reported the highest implementation of every one of
the four strategies:**
| High-poverty districts | |
|---|---|
| Continuous airflow | 51.8% |
| HVAC replacement or upgrade | 35.1% |
| HEPA in-room air cleaners | 29.9% |
| UVGI | 10.6% |
Each is above the national figure, and above low- and mid-poverty districts.
Federal money aimed at the districts with the least of it appears to have been
spent on the thing it was for — which is worth noticing precisely because the
usual result is the opposite.
By region
| Airflow | HVAC | HEPA | UVGI | |
|---|---|---|---|---|
| West | 60.2% | 40.0% | 41.6% | 9.1% |
| Northeast | 53.6% | 32.8% | 26.8% | 6.1% |
| Midwest | 46.5% | 32.3% | 22.7% | 7.1% |
| South | 46.1% | 32.1% | 25.6% | 10.6% |
The West leads on three of four. The South leads only on UVGI, the least
used strategy nationally and the one that does not depend on moving outdoor
air — which is a plausible thing to prefer in a climate where opening a window
in August is not free.
The number that limits all of this
**For all possible interventions, unknown or missing responses accounted for
28%–60% of responses.**
Up to three-fifths of answers on some measures were "don't know". These are
floors, not measurements, and the honest reading is that a district office
often could not say what had been done to its own buildings.
8,410 districts (64.2%) responded, representing **61.7% of enrolled public
school students**, out of 15,871 contacted. Larger districts (2,500+ students)
were surveyed weekly, smaller ones fortnightly. **1,358 independent charter
districts were excluded** because the poverty data used for the analysis does
not exist for them.
What follows
Federal funding remains available, and **many districts have not taken
steps to improve building ventilation.** The report's own conclusion names
what stands between the money and the buildings: **equitable access and
support might be needed to assist school districts in their efforts** — help
with the doing, not only the funding.
Source: Centers for Disease Control and Prevention, MMWR.
许可协议： CC0 1.0（公有领域） · 改编自 www.cdc.gov
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