#purificateur_d'air

  • The COVID-safe strategies Australian scientists are using to protect themselves from the virus - ABC News
    https://www.abc.net.au/news/2024-01-21/covid-safe-strategies-australian-scientists-virus-infection/103335466
    https://live-production.wcms.abc-cdn.net.au/ad2eada4eaabdc63ab704f3797c8a95b?impolicy=wcms_crop

    Some commentators have described this situation — the crashing of wave after wave of COVID-19, a steady drip, drip, drip of death and mounting chronic illness — as the “new normal”. But other experts insist it doesn’t have to be, and that continuing on the current trajectory is unsustainable — especially in light of data showing that COVID has decreased life expectancy, will cost the global economy an estimated $US13.8 trillion by 2024, and is decimating the lives of millions of people who have developed long COVID.

    Meanwhile, studies continue to pile up showing COVID-19 can cause serious illness affecting every organ system in the body, even in vaccinated people with seemingly mild infections. It can cause cognitive decline and dysfunction consistent with brain injury; trigger immune damage and dysfunction; impair liver, kidney and lung function; and significantly increases the risk of cardiovascular disease and diabetes. Then there’s long COVID, a debilitating disease that robs fit and high-functioning people of their ability to think, work and exercise.

    All of this is why governments must invest in long-term strategies for managing COVID-19 into the future, experts say — particularly by introducing standards for indoor air quality. But until then, they say, Australians can and should take precautions against COVID-19 to reduce transmission and protect their health. And doing so is relatively simple: it just takes a little planning, preparation and common sense.

    Here, three of Australia’s leading COVID-19 experts share their personal COVID safety strategies and reflect on what must happen if we’re to blunt the growing health crisis the pandemic is causing — and prepare for the next one.

    • When the COVID-19 pandemic hit Australia in 2020, Associate Professor Stuart Turville had been working in the Kirby Institute’s level-three physical containment (PC3) lab, researching another well-known RNA virus: HIV. His team quickly pivoted to #SARS-CoV-2, capturing the virus and characterising it very quickly. Still today when the NSW Ministry of Health’s genomic surveillance unit identifies a new variant of interest, Dr Turville, a virologist, will use a swab from a positive case and grow the virus to understand its mutations and virulence.

      Scientists working in the PC3 lab must wear robust personal protective equipment primarily for respiratory safety. Before he enters the lab Dr Turville dons several layers of gear: a full-face Powered #Air Purifying Respirator (PAPR) mask, a collar with its own HEPA filter ("it’s like being in a scuba suit"), two pairs of gloves, a disposable Tyvek suit, a generic gown that is laundered after use, booties, gumboots and little plastic socks that go over the boots. “Not only could [getting infected] impact our research colleagues and the general community,” he says, “but we could also take the virus home.”

      For Dr Turville, the risk of taking #COVID-19 home was particularly serious. In 2020 he was caring for his elderly father who had heart problems and his mother was also at risk of severe disease. If he brought the virus into his dad’s aged care facility, it would be put into lockdown and “he would be eating cold meals in his room alone”. “So for me personally it was incredibly important to maintain that protection and ensure I remained negative,” he says. “I’ve still only got it once — I got it from undergraduate teaching, which will teach me.”

      As for how he protects himself outside the lab, day to day? For starters, “As a scientist I don’t get out much,” he jokes. He drives to work, avoiding crowded public transport. If he’s going on an overseas trip, he’ll plan to get a booster vaccine four weeks before he gets on a plane. “I know from the studies that we do and other people do that if you get a new formulation vaccine you’re going to encourage the mature B cells to generate better cross-reactive antibodies,” he says, “and so you’re going to have better protection if you’re exposed to [COVID-19].”

      A man wearing a green lab gown stands against the wall in a corridor, next to a blue clinical smock
      Political support for genomic surveillance work is “shrinking”, says Stuart Turville.(Supplied: Richard Freeman, UNSW)
      If someone in his family gets sick, he says, they immediately isolate themselves. “It’s only happened once or twice where one of us has been positive but they’ve generally been isolated to one room and wearing a P2 mask” to protect the rest of the household. “Another thing we’ve been doing, which has been somewhat of a side benefit of looking after my father in aged care, is RAT testing before going into those facilities — even though we might be asymptomatic,” he says. “I think it’s really a situation of common sense in the context: if you don’t feel well, you isolate, you keep germs to yourself.”

      Still, Dr Turville is acutely aware of the vitriol frequently directed at people who promote COVID-19 safety. Strangers will circulate photographs of him in his lab kit, particularly on social media, to mock him: “They’ll say, ’Oh, this guy is an idiot, why is he using that, he shouldn’t fear [the virus] anymore’.” This both puzzles and amuses him. “It’s my job; I’m not going to bring it home when I have a sick father — pull your head in,” he says. “Unfortunately there is a lot of negativity towards people who choose to protect themselves. We never really saw that in the HIV era — there was never really a pushback on condom use.”

      Then again, the differences between how the two pandemics — HIV/AIDS and COVID-19 — were managed in Australia are probably quite instructive, says Dr Turville. With HIV, experts and health ministers collectively built a strong public health strategy that they strove to protect from politics. “When we look at COVID, it was political from the start and continues to be,” he says. We also now lack a “mid to long-term plan to navigate us through” this next phase of COVID-19: “Some argue that we are no longer in the emergency phase and need to gear down or simply stop,” he says. “But should we stop, and if not, what do we gear down to as a longer-term plan?”

      Three scientists wearing white Tyvek suits and full face PAPR masks working in a physical containment lab
      Stuart Turville and his colleagues working in the Kirby Institute’s PC3 laboratory.(Supplied: Richard Freeman, UNSW)
      Perhaps one reason Australia lacks a long-term plan for managing COVID-19 is the complexity of instigating one in light of the community’s collective trauma. The first couple of years of the pandemic were stressful and frightening and as much as border closures, lockdowns and other restrictions saved tens of thousands of lives in 2020 and 2021, they are still resented by some people whose livelihoods or mental health suffered — and who now push back against precaution. This backlash is so fierce in pockets of the community that some seem to conflate any kind of protective action with lockdowns.

      “There might have been some things we went too hard with but I think we have to look at it in perspective,” Dr Turville says. “We didn’t have those really, really dark months in Australia — we never had the mass graves like we saw in Italy or New York. We got a scare during [the] Delta [wave] and that helped get us our really high vaccination rates … But my worry now is, are we stepping away too soon?”

      Aside from much of the general public abandoning measures like masking, he says, political support for genomic surveillance work is also now “shrinking”. And without the critical data it generates, he says, there’s a risk scientists like him will miss new, more dangerous variants. “I think there’s a lot of patting on the back at the moment — job well done. And that’s nice, but I think it’s somewhat job well done, there goes the rug,” he says. “I think it’s the apathy that’s the concern. And I think it’s coming top-down, it’s coming very much from the government. I just don’t understand why, like we had with HIV, there can’t be a mid-term strategy.”

      ’Air is out of mind until it’s a problem’

      Robyn Schofield, aerosol scientist at Melbourne University

      A woman with blue eyes, short dark hair and green earrings smiles as a busy city rushes around her
      Robyn Schofield is an atmospheric chemist and aerosol scientist at Melbourne University.(ABC News: Danielle Bonica)
      Associate Professor Robyn Schofield can rattle off data on the harms and benefits of clean indoor air as breezily as if she were reciting her own phone number. We breathe in about eight litres of air a minute. We consume 14 kilograms of air a day. Our lungs have the surface area of half a tennis court. Globally, nine million people die from air quality issues every year. In Australia, she says, it’s somewhere between 3,000 and 11,000 deaths — “way more than the road toll”. But people generally don’t know any of that, she says. “They don’t appreciate how important breathing is until it’s hard to do. It’s like the air: you can’t see it, so it’s out of mind until it’s a problem.”

      In 2020, the air became a massive problem. The main way COVID-19 spreads is when an infected person breathes out droplets or aerosol particles containing the virus — think about aerosols as behaving similarly to smoke, lingering in the air potentially for hours. An atmospheric chemist and aerosol scientist at Melbourne University, Dr Schofield quickly began working with respiratory specialists to understand how to reduce the risk of viral transmission by improving the ventilation and filtration of indoor air.

      What she still finds thrilling is that indoor air quality can be assessed with a battery-powered CO2 monitor; popular devices like the Aranet cost about $300 but some companies are developing tech to allow smartphones to do the same. And the investment is worth it, many argue, because it can help you avoid catching COVID-19. It’s also good for productivity, with studies showing higher CO2 levels decrease cognitive performance. If CO2 is 800 parts per million, Dr Schofield says, 1 per cent of the air being inhaled has been breathed out by someone else — and is therefore a good proxy for infection risk.

      A woman pulls a 3M Aura respirator and an Aranet CO2 monitor out of her black handbag
      Dr Schofield’s COVID-safety kit includes an N95 respirator and a CO2 monitor.(ABC News: Danielle Bonica)
      One of the findings from the past few years she finds “most exciting”, however, is the role of relative humidity in indoor spaces. When relative humidity is below 40 per cent, Dr Schofield says, the risk of catching COVID-19 increases. (A good sign of that, for those who wear contact lenses, is dry eyes, which she says is “a really good indication that you should get out!”) “Because you are becoming the moisture source. Your mucous membranes — which are protecting you from getting COVID or the doses you acquire — are giving up that moisture, and so it’s easier to be infected.”

      Dr Schofield is particularly concerned with preventing infection in healthcare settings. She bravely spoke out last year when, while being treated for breast cancer at Peter Mac in Melbourne, the hospital decided to relax its masking policy for patients. “COVID cases were actually rising at the time, so it was a bad call,” she says. “And it was then reversed.” But she was still “disgusted” and lost respect for the hospital’s leadership, she says: she expected that staff would understand the science of COVID-19 transmission and take steps to protect vulnerable patients.

      A woman wearing a black top prepares to put on a white N95 respirator as people dine at outdoor cafe tables behind her
      Dr Schofield chooses restaurants with outdoor dining areas when eating out.(ABC News: Danielle Bonica)
      Even before she was diagnosed with cancer, Dr Schofield was taking precautions — for starters, she knows where the “most risky settings” are. Trains, planes and automobiles are big red zones: “Buses are actually the worst,” she says, because they recirculate air without filtering it. She regularly uses nasal sprays, wears an N95 respirator when she’s indoors with other people — in meetings at work, for instance — and makes sure air purifiers are switched on. “If I walk into a space, I will also open windows. I just go around and open them,” she says. “Because actually, no one’s going to tell me not to.”

      When eating out, she chooses restaurants that have outdoor dining areas: a newly revamped boathouse in the Melbourne suburb of Kew is a favourite of hers, and Korean barbecue is “always excellent”, she says, because there are generally extractor fans at each table. It’s all about good ventilation — clean air. “I always take my Aranet [CO2 monitor] along, and if you sit close enough to the kitchen, the kitchen fans are very effective.”

      All of these issues point to an urgent need for governments to develop indoor air standards, Dr Schofield says — for air quality to be regulated and monitored, just like food and water are. Before the pandemic, in 1998, the economic cost to the Australian economy of poor indoor air was $12 billion per year — $21.7 billion in 2021 money. “So why aren’t we learning from that, and moving forward?” she says. “This is not about going back to 2019, it’s about having the future we deserve in 2030.”

      ’We’re living in a public health ’Barbieland’

      Brendan Crabb, chief executive of the Burnet Institute

      professor brendan crabb
      The lack of action against COVID is fundamentally a problem of a lack of leadership, says Brendan Crabb.(Image: Supplied by Burnet institute)
      Four years into the COVID-19 pandemic we’re living in a “public health Barbieland”, says Professor Brendan Crabb, director and chief executive of the Burnet Institute. Too many of us are playing “make-believe” that life has returned to “normal”, he says, and there’s an “enormous disconnect” in the community: a failure to grasp both the true scale of COVID circulating and the impact of infections on our health and longevity.

      Australia recorded more than 28,000 excess deaths between January 2022 and July 2023, he says. “These are unheard of numbers, people who wouldn’t have otherwise died, let alone the hundreds of thousands in hospital — we don’t know exactly because no one publishes the numbers.” Then there are the hundreds of millions globally with long COVID-19, the risk of which increases with each infection. “I find what we know about COVID concerning enough to call it an elevated public health crisis,” Professor Crabb says. “And we need sustainable solutions to that now and in the longer term.”

      Long COVID will take your health, your wealth — then it will come for your marriage
      Long COVID is not just destroying people’s health. Behind closed doors, in homes across Australia and abroad, it is irreversibly changing relationships — sometimes for the better, too often for worse.

      An illustration in blue and pink colours shows a woman sitting alone in a room looking out a window
      Read more
      The lack of action against COVID-19, Professor Crabb says, is fundamentally a problem of a lack of leadership. “The most common thing said to me is, ’Brendan, I really do trust what you and others are saying. But if there was a real problem the prime minister, the government, would be telling us that,’” he says. “I don’t think people are all of a sudden profoundly individualistic and don’t care about COVID anymore — that they’re suddenly willing to take massive risks and hate the idea of vaccines and masks. I just don’t think they’re being well led on this issue.”

      A crucial factor shaping Australians’ apathy towards COVID-19 in 2024, Professor Crabb believes, was Chief Medical Officer Paul Kelly’s statement in September 2022 that the virus was no longer exceptional. “It is time to move away from COVID exceptionalism, in my view, and we should be thinking about what we do to protect people from any respiratory disease,” Professor Kelly said at a press conference. Those comments, Professor Crabb says, have never been turned around. “If I’m right — and I say that was a profoundly wrong statement — then that has to be corrected by the same people.”

      He also points a finger at two unhelpful ideas. “There is a strong belief, I think, by the chief medical officer and many others that once we got vaccinated, infection was our friend,” he says. Australia’s vaccine program was highly successful, Professor Crabb says. Most people were inoculated against COVID-19 before large numbers were infected. “If we were the US, we’d have had 80,000 deaths … [instead] we had 1,744 deaths in the first two years,” he says. But while vaccination broadly protects against severe illness and death, it does not protect against (re)infection or the risk of acute and chronic health problems.

      The other idea is hybrid immunity, which holds that vaccination and infection provides superior protection against severe outcomes compared to immunity induced by vaccination or infection alone. For Professor Crabb, the concept is flawed: first, because it encourages infection, which he believes should be avoided, and second, because it does not work — at least not with the predictable emergence of new variants like JN.1 which are capable of evading population immunity. “Immunity is good,” he says. “But it’s not good enough.”

      A panel of participants at the Clean Air Forum in Parliament House, with air purifiers and a CO2 monitor around the room
      Brendan Crabb took his portable air purifier to the Clean Air Forum at Parliament House last year, where there were also large purifiers in the room and a CO2 monitor on the desk.(Supplied: Stuart Kinner)
      In a perfect world, Professor Crabb says, political leaders would speak regularly about the pressure on health systems, about deaths, and about the potential health consequences for children, which are often overlooked. “And then underneath that they’d set a blueprint for action around the tools we currently have being properly implemented: a vaccine program, a clean air program, advice around wearing masks when you can’t breathe clean air, and testing so you can protect those around you and get treated.” But who speaks matters, too: “If it’s not [coming from] the prime minister, if it’s not the premiers — if it’s not consistent — it’s probably not going to cut through.”

      In the meantime, he says, people can and should take precautions — they can be leaders in their community, and start conversations with their employers and kids’ schools. For him, in addition to getting current booster vaccines, it means using a toolkit he built with his wife who, as a paediatrician who works in a long COVID-19 clinic in Melbourne, comes face to face with the harm the virus is doing every day. The kit includes a well-fitted N95 mask, a CO2 monitor and a portable air purifier. “It’s another line [of defence],” he says. “If you’re in a restaurant, say, and … you’ve got a few people around you, putting one of those on the table, blowing in your face, is a good idea.”

      Masks, he adds, should be worn in crowded places or spaces with poor ventilation. Of course, the topic sometimes sparks heated debate. A Cochrane review which last year suggested masks do not work was later found to be inaccurate and misleading and subject to an apology. But the damage it did was significant. Since then a vicious culture war has raged, much to the dismay of respected scientists who continue to make the point: numerous studies show high-quality, well-fitted N95 and P2 respirators prevent infection when they’re worn correctly and consistently.

      Professor Crabb’s home is also as “airborne safe” as he can make it. An “enormous amount of transmission” occurs in homes, he says. And his analysis of excess deaths from COVID-19 between January 2022 and March 2023 paints a striking picture: Moving down the east coast from Queensland, excess deaths increase, with Tasmania recording the highest proportion — last year it was more than double that of Queensland. “There’s no way Queensland has better COVID strategies than Victoria,” he says. “So very likely it’s to do with less time spent in poorly ventilated indoor spaces.”

      Ultimately, strong evidence supporting the benefits of clean air is why Professor Crabb believes the future of COVID-19 — and other pandemics to come — is regulating indoor air quality: a responsibility for governments, public institutions and workplaces. “That’s where we are really headed, and that’s where I think there’s strong interest at a government level,” he says. “Of course everyone is stressed about what that will cost, but … let’s at least have the conversation. We have to move towards an airborne future. How you do that in economically sensible ways is a separate discussion — whether we do it or not should not be up for discussion, and the gains are enormous.”

      #santé #prévention #CO2 #masque #purificateur_d'air #purificateur_d'air_portable

    • Ultimately, strong evidence supporting the benefits of clean air is why Professor Crabb believes the future of COVID-19 — and other pandemics to come — is regulating indoor air quality: a responsibility for governments, public institutions and workplaces. “That’s where we are really headed, and that’s where I think there’s strong interest at a government level,” he says.

    • Oui, d’ailleurs, à propos de la « régulation de la qualité de l’air intérieur, responsabilité des gouvernements, institutions publiques et lieux de travail », à Davos, ils montrent l’exemple pour la deuxième année consécutive. Le capitalisme, ça vous gagne.

    • Me serais-je mal fait comprendre ? Les purificateurs ne sont pas partout, hélas. Juste dans des endroits « stratégiques » où les dominants protègent leurs intérêts et pérennisent leurs privilèges. Un air pur et exempt de tout agent pathogène, ça se « mérite ».

    • Oui, c’est bien ce dont je parle. L’année dernière, on avait vu les images accablantes de tous des dispositifs de purification d’air pour Davos, pendant que les autres grenouillent dans les miasmes.

      On a vu aussi que « Stan » avait eu une maousse subvention qui avait dû manquer aux actions sociales pour entièrement refaire son système de ventilation.

      Je me demandais donc si on avait de nouveau vu Davos se protéger consciencieusement perdant que les dirigeants racontent à leurs peuples respectifs que la pandémie, faut vivre avec.

  • Purificateur d’air DIY : Corsi-Rosenthal Cube - Encycla
    https://encycla.com/Corsi-Rosenthal_Cube

    The Corsi-Rosenthal Cube (sometimes called a Comparetto Cube) is an inexpensive, do-it-yourself air cleaner that can be easily constructed out of a box fan and MERV-13 furnace filters. The Corsi-Rosenthal Cube can give whole-room air cleaning performance comparable to commercial HEPA air cleaners that are 10x or more the cost. Total cost is around $100USD ($130CAD).

    Construction guide
    Filter brands to potentially avoid
    Variations
    History
    Room sizing & placement
    Power usage, noise & safety
    See also
    News / media stories

    New air purifiers filter at least 90% of COVID-carrying particles, researchers say
    https://www-cbsnews-com.cdn.ampproject.org/v/s/www.cbsnews.com/amp/news/covid-air-purifiers-particles/?amp_js_v=a6&amp_gsa=1&usqp=mq331AQKKAFQArABIIACAw%3

    An army of do-it-yourselfers is trying to clear the air of COVID-19. One group at the University of California, San Diego, is building 250 homemade air purifiers for classrooms and labs around campus, and they say their box-style purifier filters at least 90% of the particles that carry the virus.

    The Corsi-Rosenthal boxes, named for the two men who created the purifiers, are made up of four air filters on the sides. As air flows in, an electric fan on top draws out the purified air.

    des équipes scolaires en fabriquent aux US et aux Canada. ça reste interdit dans pas mal d’établissements (≠DIY)

    pour ce qui est du niveau sonore ça affiche de meilleurs résultats que des soluces 20 fois plus chères du commerce. en matière d’entretien (grosse contrainte : les filtres), ça reste à voir.

    #purificateur_d'air #DIY #air #covid-19 #boites_Corsi_Rosenthal

  • How to use ventilation and air filtration to prevent the spread of coronavirus indoors
    https://theconversation.com/how-to-use-ventilation-and-air-filtration-to-prevent-the-spread-of-

    The vast majority of SARS-CoV-2 transmission occurs indoors, most of it from the inhalation of airborne particles that contain the coronavirus. The best way to prevent the virus from spreading in a home or business would be to simply keep infected people away. But this is hard to do when an estimated 40% of cases are asymptomatic and asymptomatic people can still spread the coronavirus to others.

    Masks do a decent job at keeping the virus from spreading into the environment, but if an infected person is inside a building, inevitably some virus will escape into the air.

    I am a professor of mechanical engineering at the University of Colorado Boulder. Much of my work has focused on how to control the transmission of airborne infectious diseases indoors, and I’ve been asked by my own university, my kids’ schools and even the Alaska State Legislature for advice on how to make indoor spaces safe during this pandemic.

    Once the virus escapes into the air inside a building, you have two options: bring in fresh air from outside or remove the virus from the air inside the building.

    All of the air in a room should be replaced with fresh, outside air at least six times per hour if there are a few people inside.
    It’s all about fresh, outside air

    The safest indoor space is one that constantly has lots of outside air replacing the stale air inside.

    In commercial buildings, outside air is usually pumped in through heating, ventilating and air-conditioning (HVAC) systems. In homes, outside air gets in through open windows and doors, in addition to seeping in through various nooks and crannies.

    Simply put, the more fresh, outside air inside a building, the better. Bringing in this air dilutes any contaminant in a building, whether a virus or a something else, and reduces the exposure of anyone inside. Environmental engineers like me quantify how much outside air is getting into a building using a measure called the air exchange rate. This number quantifies the number of times the air inside a building gets replaced with air from outside in an hour.

    While the exact rate depends on the number of people and size of the room, most experts consider roughly six air changes an hour to be good for a 10-foot-by-10-foot room with three to four people in it. In a pandemic this should be higher, with one study from 2016 suggesting that an exchange rate of nine times per hour reduced the spread of SARS, MERS and H1N1 in a Hong Kong hospital.

    Many buildings in the U.S., especially schools, do not meet recommended ventilation rates. Thankfully, it can be pretty easy to get more outside air into a building. Keeping windows and doors open is a good start. Putting a box fan in a window blowing out can greatly increase air exchange too. In buildings that don’t have operable windows, you can change the mechanical ventilation system to increase how much air it is pumping. But in any room, the more people inside, the faster the air should be replaced.

    CO2 levels can be used to estimate whether the air in a room is stale and potentially full of particles containing the coronavirus.
    Using CO2 to measure air circulation

    So how do you know if the room you’re in has enough air exchange? It’s actually a pretty hard number to calculate. But there’s an easy-to-measure proxy that can help. Every time you exhale, you release CO2 into the air. Since the coronavirus is most often spread by breathing, coughing or talking, you can use CO2 levels to see if the room is filling up with potentially infectious exhalations. The CO2 level lets you estimate if enough fresh outside air is getting in.

    Outdoors, CO2 levels are just above 400 parts per million (ppm). A well ventilated room will have around 800 ppm of CO2. Any higher than that and it is a sign the room might need more ventilation.

    Last year, researchers in Taiwan reported on the effect of ventilation on a tuberculosis outbreak at Taipei University. Many of the rooms in the school were underventilated and had CO2 levels above 3,000 ppm. When engineers improved air circulation and got CO2 levels under 600 ppm, the outbreak completely stopped. According to the research, the increase in ventilation was responsible for 97% of the decrease in transmission.

    Since the coronavirus is spread through the air, higher CO2 levels in a room likely mean there is a higher chance of transmission if an infected person is inside. Based on the study above, I recommend trying to keep the CO2 levels below 600 ppm. You can buy good CO2 meters for around $100 online; just make sure that they are accurate to within 50 ppm.

    Air cleaners

    If you are in a room that can’t get enough outside air for dilution, consider an air cleaner, also commonly called air purifiers. These machines remove particles from the air, usually using a filter made of tightly woven fibers. They can capture particles containing bacteria and viruses and can help reduce disease transmission.

    The U.S. Environmental Protection Agency says that air cleaners can do this for the coronavirus, but not all air cleaners are equal. Before you go out and buy one, there are few things to keep in mind.

    If a room doesn’t have good ventilation, an air cleaner or air purifier with a good filter can remove particles that may contain the coronavirus.
    The first thing to consider is how effective an air cleaner’s filter is. Your best option is a cleaner that uses a high-efficiency particulate air (HEPA) filter, as these remove more than 99.97% of all particle sizes.

    The second thing to consider is how powerful the cleaner is. The bigger the room – or the more people in it – the more air needs to be cleaned. I worked with some colleagues at Harvard to put together a tool to help teachers and schools determine how powerful of an air cleaner you need for different classroom sizes.

    The last thing to consider is the validity of the claims made by the company producing the air cleaner.

    The Association of Home Appliance Manufacturers certifies air cleaners, so the AHAM Verifide seal is a good place to start. Additionally, the California Air Resources Board has a list of air cleaners that are certified as safe and effective, though not all of them use HEPA filters.

    Keep air fresh or get outside

    Both the World Health Organization and U.S. Centers for Disease Control and Prevention say that poor ventilation increases the risk of transmitting the coronavirus.

    If you are in control of your indoor environment, make sure you are getting enough fresh air from outside circulating into the building. A CO2 monitor can help give you a clue if there is enough ventilation, and if CO2 levels start going up, open some windows and take a break outside. If you can’t get enough fresh air into a room, an air cleaner might be a good idea. If you do get an air cleaner, be aware that they don’t remove CO2, so even though the air might be safer, CO2 levels could still be high in the room.

    If you walk into a building and it feels hot, stuffy and crowded, chances are that there is not enough ventilation. Turn around and leave.

    #réduction_des_risques #ventilation #CO2 #mesure_du_CO2 #purificateur_d'air #covid-19 #coronavirus #espaces_fermés #air #contamination

    • HKU mechanical engineering study reveals airborne transmission of COVID-19 opportunistic in nature and poor indoor ventilation plays a role in transmission - All News - Media - HKU
      https://seenthis.net/messages/879105

      Germans embrace fresh air to ward off #coronavirus | Germany | The Guardian
      https://seenthis.net/messages/879381

      Ventiler, quantifier le taux de CO2, filtrer, Groupe Jean-Pierre Vernant
      http://www.groupejeanpierrevernant.info/#Ventilation

      La seconde mesure consiste à équiper tous les établissements de capteurs de CO2 de sorte à optimiser la ventilation de chaque pièce :

      fenêtre entrebâillée en permanence ou ouverte périodiquement en grand
      révision des systèmes de ventilation forcée, quand ils existent, et réglage des vitesses de ventilation

      La mesure de CO2 s’effectue à 1 m 50 ou 2 m du sol, avec un relevé au cours du temps. Le taux de CO2 doit être amené, en permanence, au niveau le plus bas possible. Un objectif quantitatif consiste à essayer d’atteindre 200 ppm de plus qu’à l’extérieur (soit 650 ppm à Paris). Les mesures préliminaires effectuées en milieu universitaire et scolaire montrent des taux anormalement élevés, y compris là où les VMC sont aux normes. Passer de 1500 ppm à 650 ppm permet de gagner au moins un facteur 5 en probabilité d’infection, et probablement beaucoup plus, par effet de seuil/de dose. Il conviendrait de fixer un maximum raisonnable (850 ppm est une valeur type recommandée par différents scientifiques) au delà duquel il faille :

      diminuer la jauge d’occupation
      ajouter un système de filtration (voir ci-dessous)
      faire réviser la ventilation forcée pour augmenter le débit
      Il convient d’avoir un recensement exhaustif des salles à risques, avec une attention particulière pour les lieux de restauration.
      Budget pour améliorer la ventilation — L’essentiel passe par des circulaires ministérielles et par une campagne de sensibilisation par des scientifiques, évitant le ton des campagnes du printemps.
      Budget pour les capteurs CO2 — Equiper chaque établissement scolaire, et chaque UFR d’un capteur CO2, produit à 50 €, coûte 3 millions €. Il faut pour cela une commande d’Etat de 60 000 capteurs-enregistreurs, et le recrutement et la formation de techniciens aidant à la mise-en-œuvre.

    • Covid-19 : l’aération, pilier jusqu’ici négligé de la prévention, c’est cité par Macron donc, Le Monde.

      https://www.lemonde.fr/sciences/article/2020/10/16/covid-19-l-aeration-pilier-jusqu-ici-neglige-de-la-prevention_6056262_165068

      Diluer par la ventilation la concentration du virus dans l’air pourrait réduire les contaminations en lieux clos. Des chercheurs proposent de généraliser les capteurs de CO2, un indice utile à condition de bien interpréter la mesure.
      Par David Larousserie

      La recommandation est tombée comme une évidence lors de l’entretien avec Emmanuel Macron, le 14 octobre, annonçant le couvre-feu en Ile-de-France et dans huit métropoles : « Aérer régulièrement (…), dix minutes trois fois par jour. » C’est, selon le président de la République, la quatrième règle barrière que tout le monde devrait suivre. L’évidence est en fait assez récente. Le Haut Conseil de la santé publique (HCSP) l’évoque dans bon nombre de ses avis, et des médecins le proclament depuis longtemps, mais la consigne restait loin derrière le lavage des mains, les masques ou les distances de sécurité. Le conseil scientifique ne l’a mentionnée que deux fois dans ses avis, à propos des municipales et des écoles.

      Sans doute cette soudaine mise en avant doit-elle beaucoup à la chancelière allemande, Angela Merkel, qui depuis plusieurs semaines insiste sur l’importance de la ventilation pour contrer l’épidémie et dont le gouvernement a prévu 500 millions d’euros d’ici à 2024 pour la rénovation des systèmes de ventilation des bâtiments publics.

      La logique de cette consigne est assez simple. Puisque le virus se transmet par l’air, diminuer sa concentration, en le diluant par un air renouvelé, abaisse les risques. Sauf que, dans le détail, la situation est plus compliquée, comme viennent d’en faire l’expérience plusieurs enseignants-chercheurs et chercheurs.

      « A la rentrée universitaire, nous voulions assurer la sécurité sanitaire de nos enseignements. Alors nous avons commencé à réfléchir de façon informelle au meilleur protocole à suivre », se souvient Bruno Andreotti, professeur de physique à l’Université de Paris, qui a participé à cette réflexion avec une poignée de volontaires, physiciens, biologistes, informaticiens… La question des masques, des gels ou de la distance étant déjà bien établie, il restait celle de l’aération.

      Situations variables

      D’abord, il a fallu arbitrer une « controverse ». Même si l’Organisation mondiale de la santé maintient que « la transmission du SARS-CoV-2 par les aérosols n’a pas été démontrée », une accumulation d’indices montre que les postillons ou les gouttes exhalées ne sont pas les seules sources de contamination, et donc que les particules qui restent dans l’air plus longtemps (les aérosols) comptent beaucoup. Par exemple, une équipe néerlandaise en juillet a montré la transmission aérienne du virus entre deux cages abritant des furets. Des infections de plus de 30 personnes à partir d’un seul malade dans des chorales en Allemagne ou aux Etats-Unis plaident aussi en faveur de ce mode de contamination. Et donc pour le bien-fondé de la ventilation.
      Ensuite, « recommander d’aérer, c’est une chose, mais savoir quantitativement si c’est bien fait, c’en est une autre », précise Benoit Semin, chercheur CNRS au Laboratoire de physique et mécanique des milieux hétérogènes, à Paris, qui a mené avec des collègues des mesures dans les salles de classe, de réunion, le métro, les voitures, les restaurants… Ces volontaires découvrent alors que, même dans une salle moderne équipée de ventilation aux normes, les situations sont très variables. Ils quantifient aussi l’effet d’une ouverture de fenêtres ou de portes. Ils constatent l’effet de la présence de 5, 10 ou 20 personnes dans une pièce.

      Comment ? Grâce à des capteurs bon marché, à une centaine d’euros, qui mesurent la concentration en dioxyde de carbone, CO2, qui est un gaz exhalé par la respiration humaine. La variation de la concentration de ce gaz permet donc de mesurer l’effet d’une ventilation mécanique ou manuelle par l’ouverture des portes et fenêtres, tout comme elle renseigne sur la présence d’humains dans la pièce.

      « Au début, nous avons suscité l’incompréhension de nos administrations », raconte Jacques Haiech, professeur honoraire de l’université de Strasbourg. « Il a fallu batailler », complète Bruno Andreotti. Les mesures montraient en effet quelques défaillances dans les ventilations…

      « Dès qu’on met un capteur dans une salle indiquant la concentration, cela crée des réflexes pour ventiler », explique Benoit Semin. « On voit même des profs annoncer qu’ils ont fait cours à tel ou tel niveau de concentration en CO2 », apprécie Bruno Andreotti. Ces campagnes de mesures bénévoles ont permis de constater qu’il faut une demi-heure environ pour qu’une personne seule fasse plus que tripler la concentration en CO2 (pour une pièce de 10 m3). Ou que dans une salle de réunion, même avec une ventilation rénovée, les teneurs en CO2 montent vite. Les ventilations ne sont en effet pas prévues pour, comme à l’hôpital, éviter les pathogènes et leur taux de renouvellement d’air est bien plus faible.

      Estimation du risque délicate

      « Les relations avec l’administration s’améliorent. Maintenant il faut passer à l’acte et s’équiper en compétence et en matériel », insiste Jacques Haiech. Plusieurs participants aux discussions et mesures ont mis en ligne un guide des bonnes pratiques sur un site critique de l’évolution de la politique de recherche, le « Groupe Jean-Pierre Vernant ». Désormais, dans plusieurs universités, les étudiants viennent en polaire en cours, leurs profs mangent la fenêtre ouverte, aèrent cinq minutes toutes les demi-heures. Le guide chiffre à 3 millions d’euros la dépense pour 60 000 capteurs, dont certains sont en rupture de stock. « On pourrait lancer des PME pour la fabrication de purificateurs d’air ou de capteurs. Mobiliser les étudiants et les profs pour faire ces mesures… », rêve Bruno Andreotti, qui peste contre l’inertie du système.

      Voilà pour les mesures. Mais, ensuite, quel seuil d’alerte fixer ? La réponse est pour l’instant impossible à donner, car personne ne sait quelle charge virale est contaminante et, a fortiori, quelle concentration dans l’air serait risquée. Deux hypothèses peuvent être avancées.

      L’une est que la probabilité d’être infecté est proportionnelle à la concentration en virus. Alors, mesurer la concentration en CO2 est une bonne manière d’estimer le risque de contamination.

      L’autre hypothèse est qu’il existe un seuil au-delà duquel on est contaminé et en deçà non. L’estimation du risque serait plus délicate, mais cela signifierait aussi qu’il est possible d’empêcher toute contamination. En 2019, une équipe taïwanaise a ainsi rapporté avoir réussi à supprimer la tuberculose dans des salles de classe correctement ventilées. Pour le nouveau coronavirus, aucun seuil ne peut encore être défini. Il semble donc imprudent, sur le plan sanitaire, de proposer des indicateurs rouge, orange ou vert en fonction de la concentration en CO2 d’une pièce, comme le suggèrent de nombreux amateurs : leurs capteurs faits maison pourraient procurer des assurances trompeuses.

      Sur la charge virale qui détermine la contamination, évoquer la thèse d’un seuil sans rappeller pas l’effet dose (cf, diminution de l’ampleur des symptômes si masques) n’est pas très sport.