those of airborne virus can be and what we can do to avoid them. opening a window is one way to keep their fresh but by keeping the air moving with systems like air conditioning are we decreasing the risk or merely spreading it. what do we need to do to breathe easily indoors. and this is the covert 19 special who are welcome to show us you can. open the window it's the one piece of advice we're all hearing now that's a bit more complicated in the winter doesn't work in all rooms and certainly doesn't work on airplanes they've used in industry says cabin air is sufficiently filtered and circulated to some experts say questions remain. for air travelers social distancing already starts to get difficult at the boarding gate and it gets even trickier on the plane spacing out just isn't possible unless you can afford to buy an extra seat. with only 50 centimeters distance between each person

the risk of infection is obvious and healing the droplets in aerosols from an adjacent passenger seems unavoidable scientists have long been aware of the dangers of infection on planes mostly because of studies of other coronaviruses air is not displaced an aircraft carrier in let's an l it's hard to small for that cabin there can only be mixed. over at the hamburg university of applied sciences professor dr schultz says viruses may stay in the cabin air for up to 15 minutes exposing passengers to infection risk. i want us to want to know what the aviation industry makes 3 crimes firstly filters an aircraft to make the air as clean as an operating room and secondly the air is completely exchanged every 2 to 3 minutes thirdly the air only moves from top to bottom in the cabin all 3 are just not sure.

it could be that current safety standards and filtration techniques are not as good as many may think meaning the possibility of catching coronavirus when flying could be more up to chance than anything else. let's take a closer look at ventilation and the virus joining me now is paul linden he's professor of fluid mechanics at cambridge university paul it's good to have you on the show. with the obvious question winter is approaching in northern in the northern hemisphere what's the best thing that someone should keep in mind about ventilation in rooms well it's obviously a challenge the winter because. c. is too close up buildings and ventilation is reduced to keep warm so the best thing to do is to make sure that as much ventilation as possible is achieved open a window if you possibly can. and if you have a mechanical system make sure as much fresh air coming in as possible what about

fans what if i just have fans that are standing around the room does that help keep things ventilators that help me at all. no it doesn't it will just mix up what's already there and that's probably not the best thing because if there is virus particles in the air in the air and start all around your chances of breathing them are increased so i wouldn't recommend using fans ok so the best option and it seems to be is to keep the window open even though it's when it's winter or least open a periodic lee. of course that's going to mean that people are going to be colder rooms are going to be colder is this really a choice now that we have between climate control and being safe with the virus is it such a black and white choice pretty much i would say it is that's right and. it's well known that during the spanish flu. classes in the u.s.

even in the midwest in the winter were held outside so it's. i think it is a it is a tradeoff between staying warm and staying safe that's going to mean quite a change for the industry the climate control. air conditioning industry yes absolutely it will and i mean conventional systems use a certain amount of research elated air and they supplement that with some fresh air when it comes to dr through the building and again you want to make sure that the proportion of pressure air is as high as possible and that will you know climate controlled situation mean of course more energy is used to keep that to warm that iraq. so it will be a trade off they have between between energy costs and. the amount of fresh air that you can provide and then one of your studies you mention carbon

dioxide of course being an indicator as well does this mean that we can expect that carbon dioxide will be a more common feature in rooms. yeah i believe that's a very sensible thing to do and our side is essentially within a building produced by people exhaling. and so levels that are above the background outside values of about 400 something past a 1000000. indicate indicative of. being in someone's lungs and then breathed out again and so measuring that gives you an estimate in fact you can relate the risk of infection directly to. the concentration of carbon dioxide help me understand your picture when i enter a room breathing speaking laughing with without a mask what am i seeing what are you seeing if you're able to see these these plumes or whatever you call them. yes so from an individual

you give off heat. every person gives off about 80 watts like a blot fairly bright light bow and that heat rises from your body in what we call a turbulent plume. and that will rise up to was the ceiling and you know that in most rooms the air in the ceiling is warmer than the air in the floor also plumes arise from equipment like a computer or other things and when you breathe out you also agree that warm air and that warm air is directed of course. in different directions so if you breathe through your nose it's directed downwards if you breathe if you talk and it goes much more was horizontally and of course it depends on the sounds that you make some sounds inject air further and louder you speak the further it goes

so there's a very complex dynamical process going on and it's invisible that's quite right we have techniques that make it possible to visualize this and we use those techniques which essentially look at the way the refractive index of the air changes it's a bit like watching the a shimmer above a toaster you look at your toaster one that you see that is the same process and we can visualize that we can see where this goes and what we do see is that if you wear a mask for example that the air that you exhale even when you're speaking we're even blocking and coughing and it tends to basically leak around. the edges of the last night's sleep around the nose where it doesn't it properly and that then gets carried out with the plume in your body and that's a good thing so that so wearing a mosque generally confines your breath to to be taken up with the hot air rising from you is more complicated if you are. and you're around on the other hand

because then you have a wake behind you just so's you would. away behind a ship and and that way you carry your breath in the wake behind you so you can spread it around quite significantly so those flows are much more vigorous than the flow produced by your ventilation system an issue very close to say an open window you probably don't perceive the around you. so those floods really run through the week the flow from your heat from your body when you speak when you breathe in and now they're much stronger and they're and so it's a complicated interaction between those flows and the general tendency of pottage to rise and and to be taken in and out through whatever openings you have in you in the building or i want to leave it there for now it sounds like a fascinating time to be a fessor of fluid mechanics paul linden joins us from william jefferson thank you very much thank you and now it's time for viewer

questions it's the part of the show where our science correspondent derek williams answers the questions you've posed that tore you tube channel over there. if a number of vaccines come out of the same time would it homy to take multiple different vaccines. in light of how quickly things are moving on the vaccine from this is an important question to ask for example there have been reports that china is apparently already giving tens of thousands of doses to people there of vaccine candidates that haven't yet completed widespread safety and efficacy testing observers are seriously alarmed by that because it sets the stage for a range of frightening possible scenarios what happens for instance if the vaccine doesn't prevent infection as well as hoped and and those people have to be vaccinated again at some point with other candidates could that be dangerous for

them the short answer is once again we don't know but possibly vaccines can have adverse effects even when just one is administered that's why they're tested so widely before being approved for the general public and with dozens of different candidates out there based on a number of different platforms there are a lot of possible combinations with the potential to go wrong if people start being given more than one vaccine or were given them in haphazard undocumented ways until we actually do it there's no way to rule out that giving vaccines in combination or in a series could pose a danger which is why it's best to exhaustively check every vaccine candidate for safety and efficiency in advance so that in a best case scenario we only have to vaccinate everyone once.

or science correspondent williams there and before we let you go here's another look at how people are adapting to life in the pandemic in this case by socially distancing within a crowd. music has returned to rio de janeiro but many dance floor is an open air concert space is selfish or spaced out boxes of up to 6 people each music fans there say it's important for their mental health to be able to let loose well hopefully staying safe. and that's it for our special we hope that you stay safe and join us next time let's watch a. kickoff

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for china starts november 6th on t.w. . this is you know we news live from berlin landmark lawsuit tech giant google in the dock the u.s. government is suing google with the trumpet ministration alleging google abuse just dominance of the online search and advertising markets also coming up curfews and closures europe tries to turn the tide scrambling to stop the coronavirus gripping the continent.