This Q&A is designed to inform members of the public about ventilation at home, offices and school, as well as when travelling in airplanes.
What is ventilation and how can it prevent COVID-19 from spreading?
Ventilation involves introducing clean air into a space while removing stale air, in order to maintain or improve air quality. Ventilation can be achieved naturally (e.g. by opening a window) or by installing a mechanical system.
The spread of COVID-19 occurs most often when an infected person is in close or direct contact with another person. The risk of the spread of the virus is higher in crowded and poorly ventilated spaces where people spend long periods of time together in close proximity. Improving indoor ventilation can reduce the risk of the virus spreading indoors.
Ventilation is not a standalone measure and it should be implemented as part of a comprehensive package of measures, such as physical distancing, wearing a mask, frequent hand cleaning, and coughing or sneezing into a bent elbow. Each of these is important to protect you against COVID-19 infection. Find out more about how to stay safe on our public advice page.
How do I naturally ventilate a room?
When you are inside with other people, open windows or doors whenever possible. For instance, try to get a cross breeze so that air coming in from one window moves across the room and exits from another window.
Can I use air conditioning or other ventilation systems?
Heating, ventilation and air-conditioning (HVAC) systems are used to maintain indoor air temperature and humidity at healthy and comfortable levels. A well-maintained and operated system can reduce the spread of COVID-19 in indoor spaces by increasing the rate of air change, reducing air recirculation and increasing the amount of outdoor air coming in. Settings that recirculate the air should not be used. HVAC systems should always be regularly inspected, maintained, and cleaned.
How can I improve heating and air conditioning systems at home?
Non-ducted heating and air conditioning units that recirculate air, such as fan-coil or split units, should be assessed, maintained and cleaned according to manufacturer recommendations. Assess the unit’s filter and consider replacing the existing filter with MERV14/F8 or the highest compatible filter with the filter rack, in collaboration with an HVAC professional. The units and filters should be periodically cleaned and maintained according to manufacturer recommendations.
More information is available here.
Can fans be used safely inside?
Air blowing from an infected person directly at another person in a closed space increases the risk of the virus spreading from one person to another.
If COVID-19 is circulating in your community and the use of a table or pedestal fan is unavoidable, it is important to regularly bring in air from outside by opening windows or doors, while minimizing how much air blows from one person (or group of people) to another person (or group of people).
The use of ceiling fans can improve the circulation of air from outside and avoid pockets of stagnant air forming indoors. However, it is critical to bring in air from outside when using ceiling fans, such as by opening windows.
How can I improve ventilation at home if someone is sick and isolating there?
If someone is sick and being cared for at home, here are some precautions to take:
- The ill person should stay in a separate room. If this is not possible, then keep at least a 1-metre distance from them. The sick person and anyone else in the same room should wear a medical mask.
- Provide good ventilation in the room of the ill person and shared spaces, and open windows if possible and safe to do so.
- Use cross ventilation to increase natural air movement by opening windows or doors on both sides of the room.
- If possible, block air from moving from the sick person’s room to the rest of the house.
- If available, choose a room with a private toilet with an air extractor or exhaust fan, which should run at a high speed.
- As a supplement, you can use a stand-alone air cleaner with a MERV14/F8 filter. These devices may improve air quality but are not a replacement for ventilation.
Also see WHO’s Q&A on homecare .
How can ventilation reduce the risk of contracting COVID-19 in airplanes?
Most airplanes have cabin air filtration systems equipped with HEPA filters which can remove viruses and germs quickly, minimizing how long people are exposed to any potential infectious virus or bacteria expelled by a cough or sneeze. Cabin air systems are designed to operate most efficiently by delivering approximately 50 percent outside air and 50 percent filtered, recirculated air. The air supply is essentially sterile and particle-free. However, adequate ventilation is just one of the preventive measures to reduce the risk of COVID-19 transmission. Other important measures include maintaining physical distance of at least 1 metre whenever possible, wearing a mask, frequent hand hygiene and wearing a mask.
What is WHO doing to address ventilation in the context of COVID-19?
Since January 2020, WHO has provided recommendation on ventilation in COVID-19 guidance. Early in the pandemic, WHO established the WHO Environment and Engineering Control Expert Advisory Panel (ECAP) for COVID-19 to review available scientific evidence and practices and update recommendations on environment and engineering controls. This multidisciplinary network brings together technical experts from various fields, such as infection control specialists, engineers, architects, aerobiologists and environmental experts.
In June 2020, WHO contributed to guidance on ventilation and air-conditioning systems in the context of COVID-19, available here. WHO works closely with the World Meteorological Organization Joint Office for Climate and Health and the United States National Oceanic and Atmospheric Administration (NOAA) through the Global Heat Health Information Network to develop and update this guidance.
In February 2021, WHO published a roadmap to improve ventilation.
