There are various ways to ventilate an indoor area: by leaving windows open at a tilt, by opening ventilation grilles or gaps, or by using mechanical ventilation systems. Airing out an indoor space is also a form of ventilation. For example, you can open windows and doors across from each other and leave them wide open for 10 to 15 minutes. This is a good idea after cooking, showering or hosting several people in the same space. Airing out the room is a way to let in lots of fresh air at once.
Humidity and COVID-19
A good balance of indoor humidity can help reduce the risk of spreading COVID-19. Especially on (very) cold days in winter, the air inside your house can get very dry. Try to keep the humidity between 40-60% (if necessary, this can be measured with a humidity meter; some thermostats can also measure it). Having many plants in your home can help you achieve good indoor humidity. If the air gets very dry, you can let the laundry dry in the room. In other seasons of the year, or in buildings where it is often too humid inside, this is usually not necessary. There are still many questions about the role of low humidity in the spread of the coronavirus SARS-CoV-2. The recommendation to achieve a good balance in indoor humidity is given as a precaution. However, there is no reason to leave the room or to call the Municipal Public Health Services (GGDs) or the municipality if it is temporarily very dry in the house.
When the weather is warm, you may want to use a fan or air conditioner to cool your home. Keep in mind that these devices do not introduce fresh outdoor air, but only move the indoor air around. If you have guests in your home, make sure that your devices are not creating an air flow from one person to another. See also the National Heat Plan.
Portable air purifiers
Air purifiers can reduce any viruses or bacteria present in the air flowing through the device. They achieve this by blocking viruses and bacteria (for example using filters) and/or killing them (for example using UV-C). A portable electrical device that can be placed in a room is called a standalone or portable air purifier. It is not yet known whether this type of air purifier prevents or reduces transmission of the coronavirus SARS-CoV-2 in public places or at home, in the context of sufficient ventilation. Similarly, it is unknown how an air purifier situated in a different part of the room might affect transmission of the virus between two people who are less than 1.5 metres apart. This also applies to transmission via hands and surfaces.
Air purifiers are not an alternative to ventilation. Ventilating brings in fresh outdoor air to replace stale indoor air. Air purifiers remove particles from indoor air, but do not introduce fresh air from outdoors. To ensure a pleasant and healthy indoor climate, a space should in any case comply with the applicable regulations for ventilation. Also, air purifiers and ventilation cannot be used as suitable replacements for the basic rules to prevent the spread of COVID-19. It is still important to stay home and get tested if you have symptoms, keep distancing, and maintain good hand hygiene. These measures are aimed at preventing all forms of transmission. They prevent infection with the coronavirus SARS-CoV-2. RIVMNational Institute for Public Health and the Environment does not play any role in approving or advising a particular type of air purifier.
What are RIVM’s recommendations about ventilation?
At a minimum, RIVM recommends compliance with the requirements of the Dutch Buildings Decree (Bouwbesluit) and all current recommendations and guidelines. In addition, RIVM recommends the following:
- Ventilate indoor spaces 24 hours a day
- Use and maintain the ventilation system according to the user manual
- Check that the ventilation capacity for the space is suitable for how it is being used
- Consult an expert if you are unsure whether ventilation is sufficient
- Air out indoor spaces regularly (between meetings or classes, during breaks).
See the LCI website for a full list of recommendations (in Dutch only).
Questions about ventilation
Can ventilation prevent the spread of COVID-19?
Good ventilation is important for a healthy indoor climate. Ventilation also helps to limit transmission of respiratory infections, such as COVID-19. However, the degree to which ventilation (refreshing the air) specifically inhibits the transmission of COVID-19 is unknown. This is why it remains important to follow the general recommendations as well: get tested if you have symptoms, keep distancing, and wash your hands.
Are there special recommendations for ventilation in care homes, cafés and restaurants, sports clubs and schools?
The Dutch Government provides information about ventilation of buildings. RIVMNational Institute for Public Health and the Environment also has general information available about hygiene, ventilation and indoor environments. Additional recommendations are available specifically for schools and care homes.