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What ventilation is and why it is important

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).

When someone with COVID-19 breathes, speaks, coughs or sneezes, they release particles (droplets and aerosols) containing the virus that causes COVID-19. While larger droplets fall quickly to the ground, aerosols containing the virus can remain suspended in the air. If someone breathes in virus particles that are suspended in the air, they can become infected with COVID-19. This is known as airborne transmission.

In poorly ventilated rooms the amount of virus in the air can build up, increasing the risk of spreading COVID-19, especially if there are lots of infected people in the room. The virus can also remain in the air after an infected person has left.

Bringing fresh air into a room and removing older stale air that contains virus particles reduces the chance of spreading COVID-19. The more fresh air that is brought inside, the quicker any airborne virus will be removed from the room.

Ventilation is most important if someone in your household has COVID-19 or if you are indoors with people you do not live with. You can pass COVID-19 on to others if you only have mild symptoms or even no symptoms at all.

Good ventilation has also been linked to health benefits such as better sleep and fewer sick days off from work or school.

Ventilation does not prevent COVID-19 from spreading through close contact and is only one of the actions you can take to stay safe and help prevent the spread of COVID-19.

Minimise the amount of time you spend indoors with people you do not live with
To reduce the risk of catching COVID-19, or passing it on, minimise the amount of time you spend indoors with people you do not live with. Meet outside if possible. If you do meet indoors, make sure the space is well ventilated. Avoid spending time with people you do not live with in spaces with a limited flow of fresh air, such as rooms without ventilation or windows that are never opened. The risk is greater in small rooms as the concentration of virus in the air can build up more quickly than in larger areas.

What you can do to improve ventilation

How you maintain or improve ventilation will depend on the 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.

Ventilate your 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).

Make sure 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.

If possible, maintain openings throughout the day to allow a constant flow of fresh air into the home. The weather can affect the amount of air that flows through openings and so these should be adjusted to balance warmth with the amount of ventilation, where possible.

If someone is self-isolating
If someone is self-isolating, keep a window slightly open in their room and keep the door closed to reduce the spread of contaminated air to other parts of the household. If the person that is self-isolating needs to use any shared space in the home, such as the kitchen or other living areas while others are present, keep these spaces well ventilated, for example by opening windows fully during their use and for a short period after they have left.

There is further guidance for households with possible or confirmed coronavirus (COVID-19) infection.

If someone is working in or visiting your home
If you have people working in or visiting your home, let as much fresh air into your home as possible without getting uncomfortably cold while they are there, and for a short period before they arrive and after they have left.

Keep warm

Ventilating your home does not mean that it has to be cold. You should keep the temperature in the room you are in to at least 18ºC as temperatures below this can affect your health, especially if you are 65 or older, or if you have a long-term health condition.

In colder weather, where it is not comfortable to leave windows open fully, opening the windows slightly can also provide ventilation and reduce cold drafts.

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.

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. Set ventilation systems to bring fresh air in and not recirculate indoor air. Devices that only recirculate indoor air will not remove airborne virus from the home. You can use the boost mode (if available) to increase ventilation if someone in your household is self-isolating due to COVID-19 or if you meet people you do not live with indoors.

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.

Ventilation in the workplace and non-domestic settings
Ventilation should be considered alongside other control measures to reduce the risk of COVID-19 transmission within your workplace or public indoor space.

It is important to identify and deal with areas that are not well ventilated. The more people occupying an area that is poorly ventilated, and the longer they remain in it, the greater the risk of spread of COVID-19.

Control measures such as avoiding certain activities or gatherings, restricting or reducing the duration of activities, providing ventilation breaks during or between room usage should be considered alongside ventilation for reducing the risk of airborne transmission.

Any actions to improve ventilation should not compromise other aspects of safety and security (for example, avoid propping open fire doors), and should consider other consequences such as health and wellbeing impacts from thermal discomfort.

Employers should provide employees with clear guidance on ventilation, why it is important, and instruction on how to achieve and maintain good natural ventilation or to operate systems if there are user controls.

The Health and Safety Executive provides advice on working safely and ventilation and air conditioning.

Make sure mechanical ventilation systems are maintained in line with manufacturers’ instructions. Set ventilation systems to using a fresh air supply and not recirculating indoor air, where possible. Assessing the requirement and performance of ventilation systems in many environments requires engineering expertise. In addition, ventilation design may be specific to the setting. For some existing and older buildings, ventilation systems may not have been designed to meet current standards and additional mitigations may be needed. If you are unsure, seek the advice of your heating, ventilation and air conditioning (HVAC) engineer or adviser.

Detailed ventilation guidance for workplaces and public buildings during the pandemic is provided by the Chartered Institution of Building Services Engineers (CIBSE).

Ventilation in vehicles

Like buildings, enclosed vehicles including cars, vans, and buses can also be high-risk for spreading COVID-19. It is important that vehicles are well ventilated to help reduce the risk of spreading COVID-19.

Follow guidance on safer travel for passengers if you need to travel. Where you need to travel, consider walking or cycling if you can.

When operating or travelling in vehicles:

  • Switch ventilation systems on while people are in the vehicle – set to drawing fresh air in, not recirculating air
  • To improve ventilation, windows can also be opened (partially if it’s cold) – heating can be left on to keep the vehicle warm
  • For vehicles that carry different passengers, such as taxis, clear the air between different passengers or at the journey end so the vehicle is aired before anyone else gets in
  • 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

Further guidance on safer transport for operators and taxis and private hire vehicles is available. The Health and Safety Executive also has advice on ventilation in vehicles.

This guidance is of a general nature and should be treated as a guide. In the event of conflict between any applicable legislation (including the health and safety legislation) and this guidance, the applicable legislation shall prevail.

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