UKHSA: What ventilation is and why it’s important
Advice from the UK Health Security Agency (UKHSA)
Ventilation is the process of introducing fresh air into indoor spaces while removing stale air. Letting fresh air into indoor spaces can help remove air that contains virus particles and prevent the spread of coronavirus (COVID-19) and other respiratory infections such as flu. Good ventilation has also been linked to health benefits such as better sleep and concentration, and fewer sick days off from work or school .
When someone with a respiratory viral infection breathes, speaks, coughs or sneezes, they release small particles (droplets and aerosols) that contain the virus which causes the infection. These particles can be breathed in or can come into contact with the eyes, nose, or mouth. The particles can also land on surfaces and be passed from person to person via touch.
While larger droplets fall quickly to the ground, aerosols containing the virus can remain suspended in the air for some time, including after an infected person has left the area. In poorly ventilated rooms the amount of virus in the air can build up, increasing the risk of spread, especially if there are lots of infected people in the room. The risk of airborne transmission is increased when occupants in an enclosed space are participating in energetic activity, such as exercising, or when they are shouting, singing or talking loudly.
Bringing fresh air into a room and removing older stale air that contains virus particles reduces the chance of spreading respiratory infections. The more fresh air that is brought inside, the quicker any airborne virus will be removed from the room.
Ventilation does not prevent the spread of respiratory infections through close contact and is only one of the actions you can take to live safely with respiratory infections, including COVID-19 .
What you can do to improve ventilation
How you maintain or improve ventilation will depend on the space and building. Buildings are ventilated by natural systems such as vents, windows and chimneys, or by mechanical systems such as extractor fans or air conditioning, or a combination of both. Where it is not possible to bring in more fresh air, a high efficiency particulate air (HEPA) or ultraviolet (UV) air cleaner could in some cases be useful for reducing the risk of infection.
- Ventilate your home
- Ventilation in the home is most important when someone in your household has COVID-19 or another respiratory infection, or when you have visitors to your household.
- Natural ventilation in the home
- Opening windows and doors at home is the simplest way of improving ventilation for most people.
If windows have openings at both the top and the bottom (such as sash windows), using just the top opening will help incoming fresh air warm up as it mixes with room air, reducing cold draughts. In warmer weather, use both the top and bottom openings as this will help provide even more airflow. Opening windows and doors at opposite sides of your room or home will also provide a good flow of fresh air (this is known as cross ventilation).
Check whether trickle vents (small vents usually on the top of a window) or grilles are open and not blocked. Air which flows in from these vents will mix with warm room air as it enters, which helps keep the room a comfortable temperature.
Windows do not need to be open all the time to improve ventilation. Bringing fresh air into a room by opening a door or a window even for a few minutes at a time helps remove older stale air that could contain virus particles and reduces the chance of spreading infections.
Ventilating your home does not mean that it has to be cold. If you are 65 or older, or if you have a long-term health condition, you should keep the temperature in the room you are in to at least 18°C, although you may prefer it to be warmer than this. Consistent house temperatures at or below 18°C may also affect the health of younger people and those without long term health conditions.
In colder weather, where it is not comfortable to leave windows open fully, opening the windows slightly can also provide ventilation and lead to fewer cold draughts. The weather can affect the amount of air that flows through openings. In cold or windy weather a smaller opening can be as effective at bringing fresh air in as a larger opening when the weather is calm and warm.
There is advice available about how to keep warm and well. If you are having difficulty heating your home, you may be able to claim financial and practical help even if you don’t own the property. Visit the Simple Energy Advice website for information about the help that is available or call their helpline on 0800 444 202. Ofgem has further advice on what to do if you are struggling to pay your energy bills.
When looking to bring in fresh air, you should think about other aspects of safety and security (for example, not propping open fire doors).
Mechanical ventilation in the home
If your home has a mechanical ventilation system, make sure this is working and maintained in line with manufacturers’ instructions. Setting ventilation systems to bring fresh air in and not recirculate indoor air will help to remove virus particles. Devices that only recirculate indoor air will not remove airborne virus from the home.
If someone in the household is unwell with a respiratory infection
If someone in the household is unwell with a respiratory infection, keeping a window slightly open in their room and the door closed will help to reduce the spread of contaminated air to other parts of the household. If they need to use any shared space in the home, such as the kitchen or other living areas while others are present, keeping these spaces well ventilated, for example by opening windows fully during their use and for at least 10 minutes after they have left will also help.
If you have a mechanical ventilation system in your household, you can use the boost mode (if available) to increase ventilation if someone in the household is unwell with a respiratory infection. Ventilation can also be increased by leaving extractor fans in bathrooms, toilets and kitchen areas running for longer than usual, with the door closed, after someone has been in the room.
There is further guidance for people who have symptoms of a respiratory infection, including COVID-19 .
Ventilation in the workplace and non-domestic settings
Good ventilation can reduce the spread of respiratory infections, including COVID-19, in the workplace and non-domestic settings.
The Health and Safety Executive (HSE) provides guidance on how to assess and improve ventilation in line with health and safety requirements under Workplace (Health, Safety and Welfare) Regulations 1992 . There is further information on actions employers can take to reduce the spread of respiratory infections in the workplace . Detailed COVID-19 specific guidance for workplaces and public buildings is provided by the Chartered Institute of Building Services Engineers (CIBSE) for those who wish to put additional measures in place .
Assessing the requirement and performance of ventilation systems in many environments requires engineering expertise. If you are unsure, seek the advice of your heating, ventilation and air conditioning (HVAC) engineer or adviser.
Air cleaning devices are not a substitute for good ventilation, however where it is not possible to maintain good ventilation, air cleaning units utilising HEPA filters or UV technologies could be a useful alternative for reducing airborne transmission of viruses. Things to consider when using air cleaning devices include whether the unit will be appropriate for the size of the area and other factors, such as noise and maintenance. CIBSE has also produced guidance on air cleaning technologies.
Any actions to improve ventilation should not compromise other aspects of safety and security (for example, not propping open fire doors), and should consider other consequences such as health and wellbeing impacts from thermal discomfort.
Where it is not possible to provide ongoing good ventilation, you may wish to consider other measures to reduce the risk of airborne transmission. These include, for example, avoiding certain activities  in that space, providing ventilation breaks during or between room usage, or using a UV or HEPA air cleaning device.
Ventilation in vehicles
COVID-19 and other respiratory infections can spread when people are travelling in enclosed vehicles including cars, vans, and buses. There are actions you can take to reduce this risk:
· Open the windows. Partial opening can still help if it is too cold to open them wide, and heating can be left on to keep the vehicle warm
· Switch ventilation systems on while people are in the vehicle – set to drawing fresh air in, not recirculating air
· Opening doors where it is safe to do so will help to change the air quickly – opening windows fully can also help to clear the air in the vehicle
This advice is for guidance only. In the event of conflict between any applicable legislation (including the health and safety legislation) and this guidance, the applicable legislation shall prevail.
1] For more information: Link HERE (accessed 3 August 2022)
2] https://www.gov.uk/guidance/living-safely-with-respiratory-infections-including-covid-19 (accessed 3 August 2022)
3] https://www.gov.uk/guidance/people-with-symptoms-of-a-respiratory-infection-including-covid-19 (accessed 3 August 2022)
4] https://www.hse.gov.uk/ventilation/overview.htm (accessed 3 August 2022)
5] https://www.gov.uk/guidance/reducing-the-spread-of-respiratory-infections-including-covid-19-in-the-workplace (accessed 3 August 2022)
6] https://www.cibse.org/emerging-from-lockdown (accessed 3 August 2022)
7] https://www.cibse.org/knowledge-research/knowledge-portal/covid-19-air-cleaning-technologies-v1 (accessed 3 August 2022)