Families in the UK are preparing for the long-awaited period of “Christmas bubbles” and five days in which a number of households will be allowed to mingle indoors.
But with the prime minister and his scientists urging people to keep things “short, small and local”, many elderly relatives are keen to make their homes as “safe for COVID” as possible.
One of the ways to reduce the risk of coronavirus spreading indoors is to make sure there is good ventilation.
Experts from the government’s Scientific Advisory Group on Emergencies (SAGE) have issued guidance on how to properly ventilate your home.
Here Sky News takes a look at what the experts said.
Why is ventilation important?
COVID-19 it spreads through small drops that are released when someone with the virus breathes through their nose or mouth.
SAGE’s advice states: “If people spend long periods of time in a room, the virus can build up in the air and people can inhale enough of it to cause infection.”
They define ventilation as “the process of bringing in fresh air from outside and removing air from inside, which may contain pollutants… including viral particles”.
So, if a room is well ventilated, there is a better chance that any particle of coronavirus in the air can pass out quickly before it can infect someone.
When is ventilation most important?
Government experts say the risk of COVID-19 particles being inhaled “appears to increase when people engage in activities such as high-intensity exercise, singing or speaking aloud.”
This is due to the fact that it “causes them to breathe more aerosols”.
So if you plan to do any of these things indoors, especially with elderly or vulnerable relatives, ventilation is all the more important.
SAGE also notes that face masks “reduce the amount of virus emitted into the air.”
At home, people are less likely to wear face masks, especially since at least part of their time will be spent eating and drinking.
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How can I ventilate my house?
“Opening windows will be the easiest way to increase ventilation for most people,” according to government experts.
Therefore, keeping as many windows and doors open as possible is the easiest way to ensure good ventilation and reduce the risk of transmitting the virus.
But if the weather is cold, it is too noisy outside or you can not leave the windows open for security reasons, it may not be practical.
In these cases, SAGE says that “regular ventilation of a room by opening windows for shorter periods of time can be effective in reducing virus concentrations in the air.”
He suggests opening them for 10 minutes every hour.
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Experts also say that you do not necessarily have to have windows and doors wide open for efficient ventilation.
“Ventilation rates through openings are determined by wind speed and the temperature difference between indoor and outdoor,” says SAGE.
“In colder weather, opening the window a small amount can lead to ventilation almost as efficient as opening the window in full in the summer.”
In addition to windows, experts recommend making sure that any “background ventilation devices” are open – which means any vents or grilles leading to the outside.
They also suggest keeping extractor fans in kitchens, bathrooms and utility rooms longer than usual after people have used the room.
SAGE says that “there is currently very little evidence” that air filters – or purifiers – are effective in preventing COVID-19.
But if you have one, be sure to use filtering or ultraviolet light, as “air cleaning principles can be useful in some cases,” it says.
When should I ventilate my house?
If you spend time indoors with people you do not live with, SAGE’s advice is: “Providing additional ventilation when visitors are at home and immediately after departure may reduce the risks if they are infected.”
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Priti Patel also says that the movement between levels is not recommended.
How are workplaces and public spaces ventilated?
In order to allow businesses to remain open during the pandemic, the British government is asking them to be “safe for COVID”.
This means conducting a COVID risk assessment, which will also include a section on ventilation.
Larger buildings have mechanical ventilation systems, which create ventilation even if there are no open windows or doors. These should be checked regularly by building staff.
These are different from air conditioning systems, which often recirculate air already in the room.
SAGE says “a number of studies have linked transmission to recirculated air conditioners.”
This is because the virus stays in the air and the speed of the air conditioner can mean that the drops “stay in the air for longer distances”.
Office fans can also have the same effect, so I do not recommend using them.
How can I tell if it’s well ventilated somewhere?
Experts admit that it is “very difficult” to determine how well it is ventilated somewhere. But there are some clues.
If you can see vents or pipes on the ceiling or on the walls, it is “very likely” that the room or building has mechanical ventilation.
A room that has no visible vents, but has windows and doors is based on natural ventilation, so if you have them open, you will ensure the space as safe as possible.
If an interior space “feels clogged or smelly,” it is unlikely to be well ventilated, says SAGE.
Experts add: “Spending a very short time in a poorly ventilated space is unlikely to pose a significant risk, especially if people wear face coverings.
“However, if you are in a poorly ventilated room with a lot of people for a long time, this is probably a much higher risk environment for transmission.”