Important update: Healthcare facilities

CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more

Find the latest information:
Recommendations for Fully Vaccinated People
COVID-19 Homepage

UPDATE

Given new evidence on the B.1.617.2 (Delta) variant, CDC has updated the guidance for fully vaccinated people. CDC recommends universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. Children should return to full-time in-person learning in the fall with layered prevention strategies in place.

UPDATE

The White House announced that vaccines will be required for international travelers coming into the United States, with an effective date of November 8, 2021. For purposes of entry into the United States, vaccines accepted will include FDA approved or authorized and WHO Emergency Use Listing vaccines. More information is available here.

Interactive School Ventilation Tool

Updated May 27, 2022

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This tool is designed for building managers or school administrators who are familiar with the school’s current ventilation systems.

Small particles that people breathe out can contain virus particles, including the viruses that causes COVID-19 and influenza (flu). Good ventilation, along with other preventive actions, can help prevent virus transmission in schools.

A window exhaust fan can reduce virus particles in a classroom by up to 95%.

We need your feedback! Help us improve this tool by taking a quick survey after using the tool below.

How can I decrease the level of particles during the school day?

Select the options below to see how particle levels change as you adjust ventilation settings.

The risk of getting COVID-19 varies according to individual susceptibility and the number of virus particles to which a person is exposed. The fewer virus particles in the air, the better.

This tool does not contain all scenarios. However, you can layer strategies for even better ventilation results.

This tool uses data from the National Institute of Standards and Technology.
The results are estimates and might not be exact in the real world. Our model assumes an infected occupant (teacher or student) inside a 790 square-foot classroom for 6 hours. The model shows the reduction in particles over those 6 hours in the classroom. To see the effects of these ventilation settings on different room sizes and HVAC system types, see this report from the National Institute of Standards and Technology.
Due to limits of the current model, the tool does not contain all scenarios, including opening a window or using multiple enhancements at one time. However, layering strategies will help clear out virus particles in rooms faster.
The model assumes that if you select Terminal Unit or Central/Rooftop Unit, the unit would be operating continuously during school hours.
The base filter in the “No HVAC” system is no filter, in the “Terminal Unit system” is MERV 6, and in the “Central/Rooftop Unit” is MERV 8. For this model, a “premium” filter is based on one rated for MERV 13 filtration. Learn more about HVAC filters and portable air cleaners. Visit Ventilation in Buildings to learn more about MERV ratings.
The portable HEPA air cleaner is assumed to be operating at high speed (300 cfm).
The exhaust fan is assumed to be 1,200 cfm.
The 100% Outside Air option is only available on the “Central/Rooftop Unit” and means that no air is recirculated.
All scenarios are compared against a classroom with no central ventilation system with no filter, no HEPA air cleaner, and no exhaust fan.

Download Data [CSV – 523 B]

Visit the Interactive Home Ventilation Tool to learn how to improve ventilation in your home.

Illustration of a classroom with virus particles in the air. The amount of particles will change based on options selected.