Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
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.
UPDATE
Travel requirements to enter the United States are changing, starting November 8, 2021. More information is available here.

Interactive Home Ventilation Tool

Interactive Home Ventilation Tool

Small particles that people breathe out can contain virus particles, including the virus that causes COVID-19.  If a guest visits your home, improving ventilation (air flow) can help prevent virus particles from accumulating in the air. Good ventilation, along with other preventive actions, like staying 6 feet apart and correctly wearing masks, can help prevent you from getting and spreading COVID-19.

How can I decrease the level of virus particles during and after a guest visits my home?

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

(To create additional scenarios, including to adjust the length of the visit and size of the home, see the expanded model from the National Institute of Standards and Technology.)

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.

Download Data [CSV – 2 KB]

Portable air filter
Image of a room
Image of a closed window
Image of an open window
Greater than 99 percent particle reduction
90% particle reduction
80 percent particle reduction
70 percent particle reduction
60 percent particle reduction
50% particle reduction
40 percent particle reduction
30 percent particle reduction
20 percent particle reduction
10% particle reduction
0 percent particle reduction
Greater than 99 percent particle reduction
90 percent particle reduction
80 percent particle reduction
70 percent particle reduction
60 percent particle reduction
50 percent particle reduction
40 percent particle reduction
30 percent particle reduction
20 percent particle reduction
10 percent particle reduction
0 percent particle reduction
HVAC auto
HVAC on/constant