Proper ventilation with outside air can help reduce the concentration of airborne contaminants, including viruses, indoors, but it should be used in combination with other best practices recommended by the CDC to protect people from COVID-19.
- Increasing ventilation can help reduce the concentration of airborne contaminants, including viruses, indoors. - Proper ventilation also reduces surface contamination by removing some virus particles before they can fall out of the air and land on surfaces. - When used along with other best practices recommended by the Centers for Disease Control and Prevention (CDC) and others, increasing ventilation can be part of a plan to protect people indoors. - Improving ventilation benefits indoor air quality by reducing exposure to products used for cleaning and disinfecting potentially contaminated surfaces. - Improving ventilation will also help control other airborne infectious diseases.
This is from EPA in 2023 at https://www.epa.gov/coronavirus/ventilation-and-coronavirus-covid-19.
Top five keywords: ventilation, coronavirus, COVID-19, indoor air quality, ASHRAE
An important approach to lowering the concentrations of indoor air pollutants or contaminants including any viruses that may be in the air is to increase ventilation – the amount of outdoor air coming indoors. Ensuring proper ventilation with outside air can help reduce the concentration of airborne contaminants, including viruses, indoors. Proper ventilation also reduces surface contamination by removing some virus particles before they can fall out of the air and land on surfaces. However, by itself, increasing ventilation is not enough to protect people from COVID-19. When used along with other best practices recommended by the Centers for Disease Control and Prevention (CDC) and others, increasing ventilation can be part of a plan to protect people indoors.
In general, the greater the number of people in an indoor environment, the greater the need for ventilation with outdoor air. In other words, the ventilation rate should be based on the number of people that occupy an indoor space (and a few other factors). In fact, CDC has stated that “Indoor spaces are more risky than outdoor spaces where it might be harder to keep people apart and there’s less ventilation.” Give special consideration to increased ventilation when occupancy is high. Also, make sure high-traffic areas have additional ventilation. In addition to helping reduce risk from airborne transmission of viruses, improving ventilation also benefits indoor air quality by reducing exposure to products used for cleaning and disinfecting potentially contaminated surfaces.
Even when community levels of infection are low or no infected person is present, improving ventilation benefits indoor air quality by reducing exposure to indoor pollutants, such as formaldehyde, nitrogen dioxide, and particulate matter (PM). Improving ventilation will also help control other airborne infectious diseases.
Read CDC's guidance on ventilation in buildings. In addition to ventilation with outdoor air, this guidance addresses other possible interventions.
Ventilation in Homes
When Additional Precautions are Necessary
When there are known or suspected cases of COVID-19 in the household, additional precautions are recommended. Refer to CDC and ASHRAE guidance on isolating COVID-19 patients and protecting people at high risk.
Opening windows and doors (when the weather permits), operating window or attic fans, or running a window air conditioner with the vent control open increases the outdoor ventilation rate in a home. Do not open windows and doors if doing so poses a safety or health risk to children or other family members (e.g., risk of falling or triggering asthma symptoms). Local bathroom or kitchen fans that exhaust air outdoors and remove contaminants directly from the room where the fan is located also increase the outdoor air ventilation rate.
- Learn more about Indoor Air in Homes and Coronavirus (COVID-19).
Learn how to decrease levels of virus particles during and after a guest visits a home. (Centers for Disease Control and Prevention's Interactive Ventilation Tool)
Ventilation in Schools, Offices, and Commercial Buildings
Most schools, offices, and commercial buildings have heating, ventilation, and air conditioning (HVAC) systems with filters on them. Typically, these systems are maintained by building or HVAC professionals. Professionals who operate school, office, and commercial buildings should consult guidance by ASHRAE (formerly known as American Society of Heating, Refrigerating and Air-Conditioning Engineers), and other professional and government organizations for information on ventilation and air filtration to help reduce risks from the virus that causes COVID-19. In general, increasing ventilation and filtration is usually appropriate; however, due to the complexity and diversity of building types, sizes, construction styles, HVAC system components, and other building features, a professional should interpret ASHRAE guidelines for their specific building and circumstances.
Increasing ventilation with all or mostly outside air may not always be possible or practical. In such cases, the effective rate of ventilation per person can also be increased by limiting the number of people present in the building in general, or in specific rooms. Administrative practices that encourage remote participation and reduce room occupancy can help reduce risks from SARS CoV-2, the virus that causes COVID-19. See ASHRAE for more information on ventilation rates for different types of buildings and other important engineering controls to manage ventilation, moisture, and temperature in a building.
Read information from ASHRAE about COVID-19. Schools and universities (pdf) (1.93 MB) Commercial buildings (pdf) (1.32 MB) Core Recommendations for Reducing Airborne Infectious Aerosol Exposure (pdf) (152.72 KB)
Clean Air in Buildings Challenge
The Clean Air in Buildings Challenge is a national call to action that highlights a range of recommendations and resources available to assist with reducing risks from airborne viruses and other indoor contaminants. Create your indoor air action plan today.
Ventilation when cleaning and disinfecting
When cleaning and disinfecting for COVID-19, ventilation is important. Choose products based on the need for cleaning vs. disinfection. If disinfecting, using EPA-registered cleaning and disinfecting products according to their label instructions is the best way to ensure that any indoor air pollution risks are reduced while still maintaining the effectiveness of the disinfecting product. In particular, follow any label precautions that recommend wearing personal protective equipment, like gloves or eye protection, designed to protect the user from the product. As a general precaution, do not mix cleaning or disinfecting products.
In general, increasing ventilation during and after cleaning, for example by opening windows or doors, is helpful in reducing exposure to cleaning and disinfection products and byproducts. Increasing ventilation can also reduce risks from particles resuspended during cleaning, including those potentially carrying SARS-CoV-2 (or other contaminants). Sensitive individuals should avoid cleaning, if possible, and consider leaving the room during cleaning. Sensitive individuals may include pregnant women and people with asthma. Also, sensitive individuals should not be present when disinfectants are being used. Store and use chemicals out of the reach of children and pets. Avoid ventilation with outdoor air when outdoor air pollution is high or when it makes your home too cold, hot, or humid. Check AirNow for information about outdoor air pollution near you.
- EPA maintains a list of disinfecting products that meet the agency criteria for use against COVID-19. View this list as well as other COVID-19 frequent questions.
Learn how to reduce your exposure to asthma triggers. Learn about the use of chemical disinfectants and sterilants by pregnant workers.
Return to Indoor Air and Coronavirus (COVID-19).