The Ventilation and Warming of School Buildings By Gilbert B. Morrison Published by D. Appleton and Company, New York ( 1887 ) Accessed 10 Apr 2024 Preface (p.xxii) ❦ ‘I am fully convinced that people are prematurely dying by thousands simply from a lack of correct and positive convictions concerning impure air; for, when the true nature of a danger is fully appreciated, the requisite means to avert it will generally be found.’ ❂ Chapter II: The Effects Of Breathing Impure Air (pp.20-23) ❦ ‘Impure air is also believed by the best authorities to be one of the principal causes of epidemics. Dr. Carpenter, than whom there is no abler authority, says: “It is impossible for anyone who carefully examines the evidence to hesitate for a moment in the conclusion that the fatality of epidemics is almost invariably in precise proportion to the degree in which an impure atmosphere has been habitually respired.” The Board of Health of New York conclude that forty per cent of all deaths are caused by breathing impure air. In view of such alarming facts, this same board declares: “Viewing the causes of preventable diseases, and their fatal results, we unhesitatingly state that the first sanitary want in New York and Brooklyn is ventilation .” Direct experiment proves that the air in our school-rooms is impure in almost all cases, and in a majority of them to a degree far beyond the danger line. In view of these facts, and the results as proved by the authorities above cited, why is it regarded by the public with such indifference? When a school-house is blown down by a hurricane, killing and maiming a score of children, it is justly regarded as a great calamity; a vacation is given to quiet the excited fears of parents and children; investigating committees are appointed to locate the responsibility, and the faces of the whole populace are blanched with apprehension. Why is this? Why does the intelligent parent send his child to a school-room poorly ventilated and crowded with children, some of whom are breathing into a stagnant air the germs of disease and death, while others, from unwashed bodies, are delivering into it their deadly emanations, and all without a protest on the part of those even who provide proper hygienic conditions at home? It is because the effects of the one are immediate, occupy little time, the number killed can be actually counted, and the exact magnitude of the calamity estimated all at once. In the other case the process is slower, but of far greater extent; the actual results are by the general public less definitely known, and custom and attention to other matters divert the attention, and the deadly destruction of the innocents by impure air goes on silently, constantly, and powerfully. While noisy demonstrations like that of the cyclone attract attention, and inspire fear and terror, it is in the silent forces that the danger lies. Nature’s most destructive forces, as well as her strongest constructive ones, are silent in their operations; but when Science detects a silent, insidious enemy to human welfare, it is not only our duty to assume an attitude of self-defense and self-protection, but it should be regarded as folly not to do so.’ ❦ On high CO₂ levels connected to poor performance in schools: ‘The effects of breathing impure air thus far considered are pathological, but it has its pedagogical and economical aspects. Every observing teacher knows the immediate relation between the vitiated air in the school-room and the work he wishes the pupils to perform. Much of the disappointment of poor lessons and the tendency to disorder are due directly to this cause. The brain unsupplied with a proper amount of pure blood [oxygen] refuses to act, and the will is powerless to arouse the flagging energies; the general feeling of discomfort, dissatisfaction, and unrest which always accompanies a bad state of the blood. From an economical standpoint it would, of course, be impossible to estimate the financial waste of breathing impure air, but it can not but be enormous. In any discussion of the feasibility of incurring the additional expense of the most perfect ventilation, this loss occasioned by the want of such ventilation must not be ignored.’ ❂ Chapter III: The Air (pp.25-26) ❦ On ventilation, air filtration, and the super-spreading of diverse diseases in classrooms: ‘Wherever an unusual amount of unwholesome matter is being evolved, there especially should the purifying conditions be present; air in such places, to remain pure, must be changed in rapid succession, in order that dilution, diffusion, and oxidation may fulfill their legitimate functions. In a school-room the contaminating process can not but be rapid, and wherever ample provision is not made for rapidly changing the air of the room a dangerous condition of affairs is sure to exist. Bacteria of many forms, and spores of fungi, are also found in the air, and all these organisms are known to thrive in the organic impurities found in the air.’ ❂ Chapter IV: Examination Of The Air (p.33) ❦ On measuring CO₂ levels as a proxy to establishing content of (infectious) re-breathed air: ‘A complete analysis of impure air comprehends the quantitative and qualitative tests for carbonic [sic] dioxide, free ammonia, and other nitrogenous matter, oxidizable matters, nitrous and nitric acids, and hydrogen sulphide; but for ordinary practical purposes the determination of the CO₂ is by far the most important, and is ordinarily the only one which need be made. While the poisonous qualities of the air are not wholly due to the presence of the CO₂ per se, the amount of this gas found to be present is, in air made impure by respiration, generally a good measure for other impurities to which the poisonous quality is principally due. Owing to this fact, a careful test for the amount of CO₂ contained in a given atmosphere is generally the only one which need be made where air is tested merely to determine its respiratory purity.’ ❂ 📖 (Accessed 10 Apr 2024 ~ D. Appleton & Company / Google Books) The Ventilation and Warming of School Buildings ➤ ❂ My thanks to Maarten De Cock for alerting me to this gem of a book. ➲

❦ A comprehensive collection of review articles regarding airborne transmission of pathogens , by Jonathan Mesiano-Crookston. ❂ Accessed : 4 March 2024 . 📖 (November 2022 ~ Geoscience Frontiers) Aerosol Transmission of Human Pathogens: From Miasmata to Modern Viral Pandemics and Their Preservation Potential in the Anthropocene Record ➤ 📖 (21 Aug 2022 ~ Indoor Air) What were the historical reasons for the resistance to recognizing airborne transmission during the COVID-19 pandemic? ➤ 📖 (31 Jan 2022 ~ Indoor Air: Editorial) Hypothesis: All respiratory viruses (including SARS-CoV-2) are aerosol-transmitted ➤ 📖 (November 2021 ~ Interface Focus) How Did We Get Here: What Are Droplets and Aerosols and How Far Do They Go? A Historical Perspective on the Transmission of Respiratory Infectious Diseases➤ 📖 (27 Aug 2021 ~ Science ) Airborne Transmission of Respiratory Viruses ➤ 📖 (August 2021 ~ Nature Reviews: Microbiology) Transmissibility and Transmission of Respiratory Viruses ➤ 📖 (July 2021 ~ Annual Review of Biomedical Engineering) Fluid Dynamics of Respiratory Infectious Diseases ➤ 📖 (14 May 2021 ~ Science) A Paradigm Shift to Combat Indoor Respiratory Infection ➤ 📖 (1 May 2021 ~ The Lancet) Ten Scientific Reasons in Support of Airborne Transmission of SARS-CoV-2 ➤ 📖 (18 Jan 2021 ~ Clinical Infectious Diseases) Airborne Transmission of SARS-CoV-2: What We Know ➤ 📖 (12 Jan 2021 ~ The Journal of Hospital Infection) Dismantling Myths on the Airborne Transmission of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) ➤ 📖 (1 Jan 2021 ~ Canadian Medical Association Journal) Mitigating Airborne Transmission of SARS-CoV-2 ➤ 📖 (November 2020 ~ Environment International) Aerosol Transmission of SARS-CoV-2? Evidence, Prevention and Control➤ 📖 (16 Oct 2020 ~ Science) Airborne Transmission of SARS-CoV-2 ➤ 📖 (1 Sep 2020 ~ Environment International) How Can Airborne Transmission of COVID-19 Indoors Be Minimised? ➤ 📖 (August 2020 ~ Anaesthesia) Airborne Transmission of Severe Acute Respiratory Syndrome Coronavirus-2 to Healthcare Workers: A Narrative Review ➤ 📖 (6 July 2020 ~ Clinical Infectious Diseases) It Is Time to Address Airborne Transmission of Coronavirus Disease 2019 (COVID-19) ➤ 📖 (June 2020 ~ Environment International) Airborne Transmission of SARS-CoV-2: The World Should Face the Reality➤ 📖 (May 2020 ~ Risk Analysis) Consideration of the Aerosol Transmission for COVID‐19 and Public Health➤ 📖 (16 April 2020 ~ The Journal of Infectious Diseases) Airborne or Droplet Precautions for Health Workers Treating Coronavirus Disease 2019? ➤ 📖 (26 March 2020 ~ JAMA) Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of COVID-19 ➤ 📖 (28 Aug 2019 ~ Encyclopedia of Microbiology) Airborne Infectious Microorganisms ➤ 📖 (31 Jan 2019 ~ BMC Infectious Diseases) Recognition of Aerosol Transmission of Infectious Agents: A Commentary➤ 📖 (September 2016 ~ American Journal of Infection Control) Generic Aspects of the Airborne Spread of Human Pathogens Indoors and Emerging Air Decontamination Technologies ➤ 📖 (15 Nov 2011 ~ Advances in Preventive Medicine) Preventing Airborne Disease Transmission: Review of Methods for Ventilation Design in Health Care Facilities ➤ 📖 (October 2006 ~ The Journal of Hospital Infection) Factors Involved in the Aerosol Transmission of Infection and Control of Ventilation in Healthcare Premises ➤ 📖 (January 1987 ~ Critical Reviews in Environmental Control) Spread of Viral Infections by Aerosols➤ ❂ © 2024 ➲ Jonathan Mesiano-Crookston . ➲

❦ SARS-CoV-2 – the virus that causes Covid-19 – is airborne. In May 2021, the WHO officially recognised that SARS-CoV-2 is airborne via microscopic aerosols – meaning that the virus is transmissible through the air at both long and short range .

❦ Every single case in which a person with Covid-19 infection infects another person in a healthcare setting – patient, relative, or hospital staff member – is a significant failure of hospital procedures.  Every single instance. ❂ © 2024 Professor Steve Robson MPH MD PhD ~ President, Australian Medical Association (AMA) . ➲

❦ We cannot individually assess the risk of infection from poor indoor air quality. Just as we cannot individually assess food safety in restaurants, or fire safety in cinemas, or aviation safety on flights. These are in the control of others, and are regulated for our health and safety. ❂ © 2024 Orla Hegarty . ➲

❦ I met a nice lady – a ward patient – yesterday who, seeing my respirator [high-filtration mask] , promptly put on her surgical mask. So instead of diving straight in to asking what was most concerning her and how I could help, I opened up a bit about infection control in hospitals. I explained how, because of a lack of respirators, March 2020 saw NHS leaders downgrade PPE for all non-ICU staff. ❂ PPE : Personal Protective Equipment. I then reminded her of the amazing DHSC 2020 and 2021 campaigns on airborne transmission of SARS2 (the green-and-black smoke ones) – and I had to point out that every IPC Lead Nurse had since had to switch off their brain and forget what they knew – and while at work, to only protect ICU staff. ❂ DHSC : Department of Health and Social Care (UK). ❂ IPC : Infection Prevention and Control. I explained that the individuals responsible for the original IPC downgrade were now authors of the national manual on IPC (NIPCM), which sets the standard for infection control in hospitals, and this manual states that airborne transmission is ‘not a thing’ for SARS2 (AGP only). ❂ NIPCM : The UK’s National Infection Prevention and Control Manual. ❂ AGP : Aerosol-Generating Procedure, ie. intubation. So hospitals are destined to be unsafe spaces thanks to the NIPCM, and the surgical mask that she was wearing was OK (ish) to help protect me – but did very little to reduce her risk of SARS2 inhalation. However, she was in a single room (an extra, and not meant as a ward-bed space – but you know, >100% occupancy forever means that you need to use your imagination) – and she already had the window open. She was appalled at what healthcare workers were being put through. She was appalled at the on-going lies. She was appalled at the possible level of harm to patients and staff from such lies. She then went on to tell me how a weekend visitor of hers had just tested positive for Covid. She was worried that they had hugged and chatted, and that she might have got infected. She’s a switched on lady, too. Lives with a medic who has the windows open all the time (“It’s freezing at home”). So I explained about the CleanAirStars.com site. About HEPA filtration being a low energy and low-cost way to remove all airborne pathogens, and to make home a safer place for... • Covid • Flu • RSV • Norovirus • Fungi Etc., etc. The list goes on and on. — “Wow, that’s like magic!” We had a very nice chat. And then we talked about her heart. I just wish I could have this same conversation with each and every NHS CEO and IPC Lead Nurse. I’d ask some questions. I’d want to know why they aren’t protecting staff as they should. I’d want to know why they aren’t protecting patients as they should. I’d want them to know that they are in breach of UK legislation. And I’d want to look them in the eye and ask them to show compassion to the powerless: to staff, and patients. Help us please. Do whatever you can to counter the lies, and to help protect the NHS. Thank-you. ❂ © 2024 Dr. David Tomlinson, NHS Consultant Cardiologist ➲ .

❦ Ms Amanda Pritchard Chief Executive Officer NHS England Sent via email 22 December 2023 Dear Ms Pritchard, Re: Need for revisions to the IPC guidance to protect healthcare workers from COVID-19 Recently, we have been hearing increasing concerns from across our respective memberships about the protection of healthcare workers and patients from COVID-19 , particularly in light of the rise in cases, hospitalisations and deaths that occurred in September and October [2023] . While it was positive to see a reduction in cases and hospitalisations in November which hopefully reflected a reduction in prevalence as well as the effect of the autumn booster programme, we are starting to see early signs that hospitalisations and cases are starting to rise again. There is no room for complacency, particularly as we deal with winter with an NHS under serious strain. In any case, suppressing the virus remains crucial to reduce the risk of new variants of concern . Moreover, the consequences of infection for some individuals remain serious. We have heard from a range of multidisciplinary clinicians from across primary and secondary care express concern about the lack of availability of even the most basic protections in many settings when they are treating patients with confirmed or suspected COVID-19 . Additionally, the BMA’s Patient Liaison Group has shared information about vulnerable patients not attending healthcare settings due to the fear of a possible COVID-19 infection . These are patients, who remain more susceptible to severe disease from COVID-19 and those for whom vaccines are less effective. As we have routinely highlighted, we believe that the existing Infection Prevention Control ( IPC ) Manual for England , and the specific IPC guidance for COVID-19 which preceded it, have contributed to the lack of protection many of our members experience. The manual does appear to recognise that COVID-19 is airborne . It states that Respiratory Protective Equipment ( RPE ), (i.e. a ( FFP ) respirator ) must be considered when treating a patient with a virus spread wholly or partly by the airborne route (2.4). However, it then makes an unclear distinction between viruses spread wholly or partly by the airborne route , and those spread wholly or partly by the airborne or droplet route where RPE is only recommended for so called “Aerosol Generating Procedures” (AGPs) – an outdated concept based on very poor evidence . Specifically , in Appendix 11, it states that a fluid resistant surgical mask ( FRSM ) is adequate protection for the routine care of COVID-19 positive patients (appendix 11), directly contradicting the statement in 2.4. It also seems very odd to make a distinction between viruses that spread only via the airborne route and those spreading via the airborne or droplet route; staff need protection from an airborne virus in both cases , in one they also need to take droplet-based precautions. The HSE’s own research from 2008 confirms a lack of respiratory protection from a FRSM . It is accepted that COVID-19 can be and is spread by the airborne route . The recent evidence given at the UK COVID-19 Inquiry clearly shows that aerosol transmission is a significant , and almost certainly the dominant, route of transmission for COVID-19 . The current guidance is therefore, at the very least, confusing and, at the worst , is recommending inadequate protection for healthcare workers treating COVID-19 patients . This continues to put them and their patients at risk of infection and, in some cases, Long Covid. We are concerned that there has been a lack of stakeholder engagement in recent months to inform updates the IPC Manual. The latest update on 25 October 2023 does not change the recommended PPE for routine care of a patient with COVID-19, although does include a new footnote seven which concerns patients with undiagnosed respiratory illness where coughing and sneezing are significant features but does not mention COVID-19 or provide guidance on recommended PPE or RPE. Stakeholders, including the signatories to this letter are seeking clarity from you about how we can engage with this process to help inform future revisions of the manual and ensure the guidance is clear and recommends adequate protection for healthcare workers. Employers ultimately have the responsibility for the safety of their workforce , under Health and Safety Law , and the IPC Manual for England references the need for risk assessments and the need to follow the hierarchy of controls. Ensuring the protection , so far as reasonably practicable, of staff who are vulnerable through exposure to the virus and any staff or patients who are individually susceptible and at risk of serious illness if they catch COVID-19 , remains a paramount legal obligation . However, the IPC guidance issued by UKHSA is mandatory in all NHS settings and settings where NHS services are provided. This makes it makes it very difficult for NHS Trusts to reconcile the confusing IPC guidance with their statutory duties as employers under health and safety legislation to provide HSE-approved RPE for protection against airborne hazards . This is especially the case as the HSE has opted not to produce its own guidance on the subject. As we deal with winter, when pressure in the NHS intensifies alongside rising flu and other seasonal respiratory viruses, as well as COVID-19, ensuring there are enough staff across the NHS is more important than ever. COVID-19 is likely to still cause significant staff absence , particularly if cases continue to rise in the coming weeks and months. Providing clear and adequate IPC guidance , including on the need for RPE and adequate ventilation , will help protect healthcare workers and patients and reduce staff absence this winter. Providing staff with adequate protection will also better protect patients and will help reassure vulnerable patients they can safely access healthcare . We would appreciate your reassurance that our concerns will be addressed and the relevant IPC guidance will be urgently updated to reflect this, as well as routinely reviewed. We are of course willing to work with your colleagues and the Chief Nursing Officer on IPC guidance. Yours sincerely, Professor Phil Banfield. BMA, Chair of Council. Dr Barry Jones. Chair of Covid Airborne Protection Alliance (CAPA). ❂ 📖 (22 Dec 2023 ~ The British Medical Association & Covid Airborne Protection Alliance) Need for revisions to the IPC guidance to protect healthcare workers from COVID-19 ➤

❦ We’ve contacted chief nursing officers in all four UK countries and the UKHSA to find out what action will be taken in response to WHO’s statement on a new COVID-19 variant of interest. The RCN is asking for a revision to current guidelines , to introduce universal implementation of the two measures advised by the World Health Organization (WHO) to help protect healthcare staff against COVID-19. Earlier this week, in light of the new COVID JN.1 variant, WHO advised healthcare workers and health facilities to: implement universal masking in health facilities , as well as appropriate masking , respirators and other personal protective equipment for health workers caring for suspected and confirmed COVID-19 patients ; improve ventilation in health facilities . The existing national infection prevention and control manuals don’t require standardised masking for COVID-19, and decisions on respiratory protective equipment are left to local risk assessments. This is now inconsistent with WHO’s latest advice . We also have concerns about the adequacy of ventilation in general ward and outpatient areas within hospital buildings and believe that action must be taken to assess and improve this. Although evidence suggests that the global public health risks from the new variant are low, WHO has warned that onset of winter could increase the burden of respiratory infections in the Northern hemisphere. This comes when there are already unsustainable pressures on the health service. Figures show that there has been a rise in COVID-19 cases and hospitalisations , and the RCN argues that without proper protections , ill health could continue to rise in nursing staff and impact their ability to deliver safe and effective patient care . WHO has advised that it is continuously monitoring the evidence and will update the JN.1 risk evaluation as needed. The RCN is urging health care employers to assess the risk posed by COVID-19 and put appropriate safeguards in place for patients and staff . Our COVID-19 workplace risk assessment toolkit aims to help assess and manage the risks associated with respiratory infections such as COVID-19, highlights the duties of nursing staff in specific roles (such as health and safety reps), has advice for employers and leaders, and provides the latest information on risk assessment. ❂ 📖 (21 Dec 2023 ~ Royal College of Nursing / RCN Magazine) COVID JN.1 variant: RCN seeks assurance on new PPE advice ➤ © 2023 Royal College of Nursing (RCN).

❦ I am now absolutely convinced that unless we reduce the transmission of Covid-19 through societal non-pharmaceutical interventions (such as cleaning indoor air) and/or the deployment and uptake of second-generation vaccines, attrition of healthcare will reach a tipping point. This tipping point – which may well happen within the next year – will lead to a global decrease in quality of available healthcare services, which in turn will lead to increased morbidity and mortality from all causes. Every government needs to reduce transmission. The denial of this problem will not change the outcome. Policymakers need to understand this. ❂ © 2023 Conor Browne ➲

❦ Coughing into one’s sleeve while in shared air is like peeing into one’s swimsuit while in shared water. ❂ © 2023 Malgorzata Gasperowicz . ➲

✻ Accessed: 4 Dec 2023. ➲ Date published: 24 Jan 2023. ➲ Date last updated: 2 Feb 2023. ❦ The UKHSA’s definition of ‘ Airborne ’, and how it applies to SARS-CoV-2 / COVID-19 : ➲ ‘ Airborne (droplet or aerosol) transmission : This occurs when an infected person coughs, sneezes, or talks (droplets) containing the infectious agent are expelled into the air and inhaled by someone nearby OR when an infectious agent is suspended in the air and inhaled by someone (aerosol) because the infectious particles are much smaller and can remain suspended in the air for long periods of time . For example flu, RSV, COVID-19 , TB, measles, C. diphtheria, Strep pneumoniae.’ ❂ ➲ [C19.Life Note ] : The accepted scientific definition of ‘airborne aerosol transmission’ most certainly also includes the act of breathing . While the UKHSA admits to close-range SARS-CoV-2 transmission via droplet (and aerosol), it neglects to emphasise far-range transmission via infectious aerosols. ❂ 📖 (24 Jan 2023 / Updated 2 Feb 2023 / Accessed 4 Dec 2023 ~ UK Health Security Agency) UKHSA Advisory Board: preparedness for infectious disease threats ~ Airborne (droplet or aerosol) transmission ➤ © 2023 UKHSA .

❦ ‘COVID patients exhale high numbers of virus during the first eight days after symptoms start , as high as 1,000 copies per minute, reports a new Northwestern Medicine study. It is the first longitudinal, direct measure of the number of SARS-CoV-2 viral copies exhaled per minute over the course of the infection – from the first sign of symptoms until 20 days after. On day eight , exhaled levels of virus drop steeply , down to near the limit of detection – an average of two copies exhaled per minute.’ ❂ 📖 (8 Sep 2023 ~ Northwestern University) COVID patients breathe large amounts of virus early on ➤ © 2023 Northwestern University, Illinois .

❦ If doctors knew that one person can breathe out 180,000 copies of the virus in ten minutes, and that most transmission is from people without symptoms, and that mild infection increases your risk of death for six months – would they mask to protect themselves? ❂ 📖 (18 Sep 2021 ~ The Times) Ventilate! Ventilate! Ventilate! How to design the breathable buildings of the future ➤ By © 2021 Orla Hegarty and Lidia Morawska. 📖 Paywall-free version (Accessed 11 Nov 2023 ~ Wotton Works) Ventilate! Ventilate! Ventilate! How to design breathable buildings of the future ➤ 📖 (21 Aug 2023 ~ Nature: Medicine) Postacute sequelae of COVID-19 at 2 years ➤ 📖 (Accessed 11 Nov 2023 ~ Jessica Wildfire) 51 Sources on Masks ➤ ❂ © 2023 Orla Hegarty ➲

❦ Whenever I hear someone ask if we’re expected to continue masking in healthcare settings forever, I immediately think of Semmelweis – the man who discovered that healthcare workers’ dirty hands were causing fever and death in patients. The result of his discovery wasn’t the widespread implementation of hand hygiene though... Instead he was shunned, ostracized, lost his job and eventually institutionalized. It took around fifty years before the life-saving value of hand-washing was fully recognized in healthcare. Fifty years. It turns out that doctors didn’t take kindly to the idea that their own hands were unhygienic – and the source of disease and death for some of their patients. Despite the evidence, the denial was rampant and it was strong. The majority consensus was that Semmelweis was a crank... The resistance to the idea that the air we exhale while caring for patients can be unhygienic, and a source of illness and death for some, feels exactly the same to me. Despite the evidence, the denial is strong. Many prefer to cling to the status quo they knew before the pandemic. But that status quo was when we didn’t know better, and when we didn’t have such a virulent and dangerous new airborne pathogen in permanent circulation. Now that we do, and now that we know better, we should be willing to do better. So if the air we breathe can be unhygienic, and cause illness and death in our patients, and we know there’s a simple, effective solution – filtering it through a respirator – then it seems logical that this would become the new standard in our clinics, hospitals and long-term care facilities. Permanently. But as with Semmelweis’ experience, I expect that suggestion to get a lot of pushback, and for it to take a very long time for the medical field to accept that the old status quo is gone, and that masking in healthcare is the new normal. I just hope it won’t take another fifty years. © 2023 Dr. Lisa Iannattone . ➲

❦ There is no such thing as “personal risk assessment” for the vast majority of people. A tiny number of dominant personalities in your life (and it could be you) have decided what to do, and the rest will follow. Even those that are making the decisions are not making a personal risk assessment. They are making a group risk assessment and taking their whole family / community with them. People may not even realise this – that they have made the decision on behalf of their entire household / class / company... but they have... If there is no responsible public health leadership, someone else is leading... because that is how we work, by and large, as a species. Someone is in charge... someone is always in charge, and unfortunately... misinformation is rife. ❂ © 2023 Dr. Noor Bari . ➲

❦ ‘The magnitude of the outbreak illustrates how younger children infected from diverse pediatric facilities can be a major source of widespread household transmission with the potential to facilitate community transmission in the era of the Omicron variant. With highly transmissible variants such as the Omicron (B.1.1.529) variant of concern (VOC) and its subvariants becoming dominant globally, the role of children in transmission dynamics needs to be elucidated to take tailored public health and social measures for the control of outbreaks and pandemics. On epidemiological investigation, frequent and intimate interactions among children, along with inadequate indoor ventilation, were commonly observed in pediatric facilities. Given the practical challenges of behavior modification among pediatric populations, including consistent and correct mask use and physical distancing, the environmental control interventions, such as improved ventilation systems, upper-room ultraviolet germicidal irradiation, or portable high-efficiency particulate air-filtration appliances, may offer sustained benefits in stemming the virus transmission in pediatric facilities.’ ❂ 📖 (20 Apr 2023 ~ Yonsei Medical Journal) Widespread Household Transmission of SARS-CoV-2 B.1.1.529 (Omicron) Variant from Children, South Korea, 2022 ➤ © 2023 Park et al / Yonsei Medical Journal.

❦ I think a big problem is that many people’s conceptions of morality do not extend to invisible viral transmission and indirect chains of harm. Punching someone in the face and bloodying their nose is unconscionable. Killing a hundred people in a chain of negligent transmission? No biggie. © 2023 Blake Murdoch . ➲

❦ ‘ Aerosol spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a major problem in hospitals , leading to an increase in supplementary high-efficiency particulate air ( HEPA ) filtration aimed at reducing nosocomial transmission.’ ➲ Note : A nosocomial infection – also referred to as a healthcare-associated infection ( HAI ) – is an infection acquired during the process of receiving healthcare that was not present during the time of admission. ‘Air-cleaning units ( ACUs ) reduce microbial contamination in ward air , demonstrating that the application of a combined HEPA/UV-C ( ultraviolet-C ) ACU on an older adult inpatient ward reduced airborne particulate matter (PM) levels substantially , most notably in the size range associated with respiratory viruses, such as SARS-CoV-2. Therefore, such devices may be applicable not only to pathogens traditionally considered airborne , such as measles and tuberculosis , but also where aerial dissemination contributes to the transmission of fungal and bacterial infections , such as with Clostridioides difficile spores. This study found that airborne particulates associated with human activity migrated considerable distances around the ward , indicating that social-distancing measures alone are unlikely to prevent the transmission of respiratory viral infections and possibly other infections that are aerially disseminated. Collectively, this suggests that appropriately-sized ACUs have the potential to reduce nosocomial infections , especially in inadequately ventilated hospital wards.’ ❂ 📖 (23 Feb 2023 ~ Journal of Hospital Infection) Impact of supplementary air filtration on aerosols and particulate matter in a UK hospital ward: a case study ➤ © 2023 Journal of Hospital Infection .

❦ What should be a higher priority for society: preventing pigs from becoming sick, or preventing human illness? Personally, I place a higher value on preventing human illness. I think most would agree. Why, then, are pig barns far better ventilated than schools? An airborne virus has killed 900,000 Americans, and has left countless others suffering from Long Covid along with its chronic, and perhaps permanent, mental and physical afflictions. We know that ventilation and the filtration of indoor air prevents illness. The manifold benefits of improved ventilation are well-documented and uncontroversial. Professor Don Milton has been publishing studies for over twenty years showing that improved ventilation reduces respiratory illnesses and absences, though his findings were largely ignored. Yet we’ve done almost nothing to improve air filtration and ventilation in schools, workplaces, restaurants, and other buildings. The USA’s CDC (Centers for Disease Control and Prevention) gives lip service to ventilation – but has issued no minimum ventilation requirements, and offers no specific guidance. 📖 (26 Feb 2021 ~ CNN Health) CDC must encourage better ventilation to stop coronavirus spread in schools, experts say ➤ On the other hand, great cost and effort is put into ventilating and filtering the air in pig barns in order to prevent disease outbreaks. Let’s compare the ventilation and air-filtration of pig barns with buildings inhabited by human beings. First, note that airborne spread of Porcine Reproductive and Respiratory Syndrome (PRRS) was readily accepted based on circumstantial evidence and lab studies. French farms even installed HEPA filtration systems in pig barns, despite “no hard data to support” their use. Contrast this with the stubborn, year-long denial of airborne Covid spread by the WHO and CDC, despite abundant evidence. The precautionary principle is obeyed when pigs’ health is at stake, but not when human health is at risk. Incredibly, droplet dogma still reigns supreme in some places. Many are still fighting against appallingly ignorant public officials and nonsensical guidelines in Australia. [Insert ubiquitous poster from your hospital, doctor’s surgery, pharmacy, bowling alley or supermarket extolling the virtues of hand-washing and hand-sanitiser in a pandemic essentially driven by aerosol transmission .] Some officials haven’t gotten the memo yet: Covid is airborne . Many careful, controlled studies of ventilation and air-filtration in livestock facilities have been carried out, and the cumulative evidence compiled leaves little doubt of their effectiveness at preventing disease in farm animals. One of many examples: 📖 (July 2006 ~ Canadian Journal of Veterinary Research) Further evaluation of alternative air-filtration systems for reducing the transmission of Porcine reproductive and respiratory syndrome virus by aerosol ➤ In contrast, before Covid, research on ventilation, air-filtration and disease in human dwellings was pretty sparse. Linsey Marr, Don Milton, Julian Tang, Yuguo Li and others were lone voices in the wilderness, shouting into a void, and ignored by the CDC and the WHO. For buildings that humans inhabit, enforced minimum ventilation requirements are almost non-existent. The HVAC* in a school or nursing home can be completely non-functional, creating a superspreader environment, and with no legal consequences. * HVAC = Heating, Ventilation, and Air Conditioning. This is not hypothetical. Here is one documented instance in which all 226 residents in a Canadian nursing home contracted Covid, resulting in over 70 deaths. 📖 (14 May 2020 ~ CBC News) Investigators look into catastrophic outbreak that infected all residents of TMR seniors' home, killing 70 ➤ The cause? A non-functioning ventilation system. And this was a less transmissible, pre-Alpha SARS-CoV-2 variant. 📖 (15 May 2020 ~ Radio Canada) Un CHSLD infecté à 100%, avec un système de ventilation en panne, préoccupe Québec ➤ The same private company owned another nursing home in which 96% of residents and 116 employees caught Covid, leading to the death of 66 residents. I think we can surmise that the ventilation in this facility was also very poor. Why were the ventilation systems in these nursing homes not audited? Because such auditing is simply not done – not in nursing homes, schools, workplaces or restaurants. Ventilation and air-filtration recommendations exist, but not enforced standards. They’re essentially voluntary. What about pig barns? While there are no legal requirements, the ventilation and air-filtration systems at these facilities are assiduously checked every day by a worker whose sole duty is to inspect and maintain the ventilation equipment. 📖 (12 Nov 2016 ~ National Hog Farmer) Hog barn filtration system audits imperative to disease control ➤ No aspect of the system is left unchecked. “Look for any gaps or openings that would allow dirty air in... Make sure chutes collapse properly, creating a good seal.” “Cracked fan housings or a broken shroud” are checked for, and “weep holes plugged with a rubber stopper...” But daily inspection is only the start. In addition, at least once a month, a system filtration technician (SFT) audits the ventilation system, coaching the on-site manager. Another monthly audit is performed by the herd veterinarian, who guides the SFT. In contrast, human dwellings (such as nursing homes) are virtually never audited, even during a pandemic. It apparently requires a court order for such an audit to occur. Are HVAC systems in human-occupied buildings well maintained? HVAC expert Jeffrey Siegel: “The best HVAC in the world performs poorly when it’s not well maintained, and the usual standard is ‘not well maintained’.” The same article* describes an HVAC unit installed upside-down in a large store, making it impossible to change the filter, meaning that “... the air inside the store would be that much crummier”. It was like “a thousand other HVAC mistakes” Siegel has seen: “... dampers supposed to admit outside air into a building rusted open or shut, badly-installed filters letting air pass around their edges, forced-air fans running 18% of the time. In theory, HVAC heats and air-conditions. In practice, it doesn’t always ventilate... or filter.” * 📖 (9 Nov 2020 ~ Wired) The Next Covid Dilemma: How to Make Buildings Breathe Better ➤ What sort of air filters are used for pig barns? First, a mesh net catches larger objects in the air, such as feathers. Then the air goes through a MERV 8 ‘pre-filter’. This pre-filter is of a higher grade than the filters used in many schools, which are MERV 7. After passing through the MERV 8 pre-filter, air entering pig barns is filtered by MERV 15 air filters – similar to the filters used in hospitals. Very few schools, workplaces, nursing homes or restaurants use anything above MERV 11. MERV 15 is unheard of. Does such high-quality ventilation and filtration of pig barns reduce disease outbreaks? Of course it does, as the extensive literature on livestock-facility ventilation and air-filtration attests. 📖 (May 2012 ~ Viruses) Evaluation of the long-term effect of air filtration on the occurrence of new PRRSV infections in large breeding herds in swine-dense regions ➤ However, there is a potential problem: what if some of the dirty air from the human-occupied office building on a farm were to leak into the pig barn? Perish the thought! To allow pigs to breathe the same filthy air breathed by humans would be unthinkable. Therefore, pig farms are designed so that none of the filthy air from the farm’s human office is allowed to contaminate the pristine, highly-filtered air of the pig barn. (“If there is dirty air in the office, it will stay in the office.”) The notion of providing pig-quality air to the office is considered so absurd that it doesn’t merit consideration. After all, if the health of the workers on a farm is improved, this doesn’t affect profits. A sick pig, on the other hand, hurts the bottom line. Priorities... One article on the ventilation and air-filtration of pig barns notes a peculiar “side benefit” of improving the pigs’ air: human workers notice the better air, and seem healthier for it. How much healthier? No-one knows, as such trivial topics as worker health are not researched. So why is the air quality in human buildings so poor? Why haven’t greater efforts been made to improve indoor air quality (IAQ), the enormous benefits of which are well-known and uncontroversial? After all, we regulate water and food safety. Why not indoor air? The WHO recommends schools and other buildings have at least 6 air changes per hour (ACH). A typical school HVAC provides less than 1 ACH. IAQ experts recommend CO2 levels be less than 800 ppm (or less than 700 ppm in a pandemic), but CO2 levels regularly reach much higher levels in schools. I’ve occasionally registered levels near 3000 ppm; others report readings higher than 4000 ppm. What about hotels? I stayed in a room at the Disney Caribbean Resort Hotel with my brother. CO2 reached well over 3000 ppm each night. I did a CO2 decay study, and found that the room got 0.11 air changes per hour. Not good. It’s long past time to greatly improve ventilation and air filtration by imposing serious, enforced IAQ standards in nursing homes, schools, workplaces and other public spaces. Many aerosol and IAQ experts have been calling for this for a long time. 📖 (14 May 2021 ~ Science) A paradigm shift to combat indoor respiratory infection ➤ Only recently have their calls gained traction. The vast majority of people would be much better off if IAQ were improved through better ventilation and filtration. We spend the majority of our lives indoors. Proper air filtration and ventilation would enormously improve the air we breathe. When we think of air pollution, we usually think of lung damage. But polluted air damages all organs of the body. With cleaner air, brain function would improve; heart attacks and strokes would fall; illness would be reduced. It works for pigs. It can work for humans, too. Air pollution is possibly the single largest health problem in the world. It causes the loss of more years of life than alcohol and narcotics, unsafe water, HIV, malaria, and war combined. Cleaning the air we breathe is essential. However, the pecuniary interests of the 1% of landlords, real-estate magnates, business owners, and capitalists in general might not be so well-served. Installing better ventilation systems and air filters in human dwellings might put a dent in their investment returns – an unthinkable notion. To sum up. Improving indoor air quality in human dwellings merely improves the health and well-being of humans – a minor consideration – while improving air quality in pig barns improves profits: a sacred objective, and the chief aim of life under capitalism. ❂ Related : 📖 (10 Aug 2020 ~ The Conversation) How to use ventilation and air filtration to prevent the spread of coronavirus indoors ➤ Related : 📖 (28 Sep 2020 ~ Quartz) What everyone should know about ventilation and preventing Covid-19 ➤ ❂ © 2022 Ryan Hisner . ➲

❦ I keep saying that someday I’ll write a book about the struggle to bring an engineering perspective to infection prevention and control in healthcare. For now... just an essay. Is there anything worse than knowing that there are oceans full of icebergs ahead; how easy it is to engineer systems to detect and steer around them; but not being able to get the owners of the liners (or anyone in command) to listen as you blindly head straight for them? I’ve been advocating for engineering solutions and standards for air, water and surfaces in healthcare facilities to lower disease transmission for over 30 years. The irony of being accused by out-of-touch ID/PH/IPAC/Epi * of epistemic trespassing before and during the pandemic is gobsmacking. * ID = Infectious Diseases / PH = Public Health / IPAC = Infection Prevention and Control / Epi = Epidemiology. I started with single patient rooms. In pre-pandemic Canada, we had the highest HAI* rate in OECD * – one in ten inpatients – and the lowest beds and lowest single rooms per capita. * HAI = Hospital-Acquired Infection, also known as a nosocomial infection, is an infection that patients get in healthcare facilities while receiving treatment for other medical or surgical conditions. * OECD = Organisation for Economic Co-operation and Development. We also had sicker patients. Studies now show that single-patient rooms cut infection rates in half. Ten years ago, Canada began moving to primarily single-patient rooms for new hospital builds – although not a hundred percent as hospitals won’t give up preferential private-room billing to insurance companies. In 2007, we formed a small group of volunteers to create a Canadian National Standard for Plume Evacuation – source control to prevent airborne transmission of disease in ORs * . * OR = Operating Room. Despite nurses’ complaints, we couldn’t get support – until doctors started getting genital warts in their noses. We helped ISO * develop a similar global standard which was published in 2014. * ISO = International Organization for Standardization. Because laser and electrocautery smoke is clearly visible, and there are now national and international standards, the practice of source control in ORs is now well-accepted. Unlike smoke, our breath is not visible – and there are no national or international standards yet for pathogen-free air. However, the principle of air extraction would work in ICUs * and patient rooms just as well as ORs. * ICU = Intensive Care Unit. Copper was registered as an antimicrobial in 2008, 50 years after silver. Over the past ten years, countless studies have shown efficacy, persistence, durability and the safety of copper surfaces – but the ID community pushes back with objective conclusions like “... Too good to be true”. While ID/IPAC has no budget of their own to implement engineering measures in hospitals, in Canada they can (and most often do) scuttle initiatives in Engineering and Facilities Management, and in Environmental Services departments, to introduce new technologies and materials to combat HAIs. In 2011, I pursued the concept of combining continuous and high-frequency bioburden reduction of surfaces to prevent fomite transmission. Copper could provide ‘continuous’ reduction on high-touch surfaces, while UV * (if automated) could provide ‘high-frequency’ reduction on all surfaces. * UV = Ultraviolet (UV) radiation. In 2014 we launched AutoUV – built-in fixtures that detected occupancy, monitored whether doors were open or closed, and dosed rooms every four hours and after every exit. As expected, it works. It can’t not work. And after seven years in the field, it’s been shown to be extremely safe. Bathrooms can be the source of half of disease spread in hospitals. C diff * can be colonized in air after every toilet flush. Aerosols drift for minutes to hours. Intestinal and respiratory diseases are often spread through toilet aerosolization. * C. diff , also known as Clostridioides difficile or C. difficile , is a gram-positive bacterium that can cause diarrhoea and colitis. AutoUV? Bathroom source-control. Today, there are thousands of units in use across Canada – and the Ontario Ministry of Health has made AutoUV a standard-of-care for new hospital builds. MOHLTC * now mandates and funds AutoUV. * MOHLTC = Ontario Ministry of Health and Long Term Care. Hooray. But IPAC stubbornly pushes back against the use of AutoUV. In other ironic news, Health Canada is cutting off use of open-air UV in healthcare, including Upper Air UV – in the middle of an airborne pandemic – due to a flood of household UV devices that are being sold retail and online that don’t work, don’t have safety certificates, or produce [dangerous] ozone. In 2014 I co-founded CHAIR – the Coalition for Healthcare-Acquired Infection Reduction – a group of scientists, engineers, ID doctors and industry partners working together to engineer air, water and surfaces in order to lower HAIs. We naively thought that we could achieve an 80 percent decrease in preventable, environmental HAIs with new technologies and materials. We knew legacy industry players in chemical disinfection would be a challenge. We had no idea that the biggest battle would come from the ID/IPAC community itself. I watched in horror at the denial of airborne transmission of 2003 SARS at a plenary session in Toronto in May 2014. Playing to the crowd in a purposeful, dismissive and comedic way, the speaker claimed that “SARS is not airborne . The droplets fall to the floor within six feet.” Dr Yu, of Hong Kong Public Health, had only just re-analyzed and re-published the Amoy Gardens study six months earlier on the 10-year anniversary reaffirming airborne transmission of [the original 2002-2004] SARS. When I challenged the speaker, he exclaimed: — “Oh, don’t worry. I know him. He's changed his mind.” In 2014, an ID doc from PHO * presented at a Toronto IPAC Education Day. * PHO = Public Health Ontario. He claimed that Ebola was definitely not airborne . When challenged with a study showing transmission between caged and separated laboratory primates, he replied: — “Well, monkeys have long arms. Besides, they can spit.” In a follow-up from me: “There’s airborne transmission of PRRV * in hogs between factory farms kilometers away, and documented in Veterinary journals...” * PRRV = Porcine reproductive and respiratory syndrome virus. — “I don’t read those journals.” — “Would you like me to send you some articles?” — “Don’t bother.” They don’t want to know. Hospitals are a global network of MDRO * incubators. * MDRO = A multidrug-resistant organism (MDRO) is a germ that is resistant to multiple types of antibiotics, making it difficult to treat and cure infections. CDI * and MRSA * initially tend to spread in hospitals before seeding community-acquired versions. Sinks and drains are known sources of contamination, especially via the aerosol route. Pathogens are getting more virulent – including MDRO/CPE/CRE/CPOs and C auris. * CDI = Clostridioides difficile infection (CDI or C-diff), also known as Clostridium difficile infection, is a symptomatic infection due to the spore-forming bacterium Clostridioides difficile. * MRSA = Methicillin-resistant Staphylococcus aureus (MRSA) infection is caused by a type of staph bacteria that's become resistant to many of the antibiotics used to treat ordinary staph infections. Water contamination and aerosolization, and bacterial, fungal and biofilm reservoir control = Engineering. Progressive examples: ➲ In Calgary Health Region: UV all incoming water? No Legionella. Self-disinfecting sinks? Electrocatalytically-split H2O into OH-, O-, O3 and H2OH = Disinfectant. ➲ In Ontario, the Ministry of Health now funds and mandates self-disinfecting sink and drain technologies. However, IPAC/ID continue to push back against new technologies. So why write this essay? Because the current struggle to recognize airborne transmission, and the engineered solutions, is part of an epic struggle. We’ve seen how much resistance there has been in almost two years. The entrenchment started a century ago, as most of us know. But the struggle has been about much more than “airborne” . It’s a struggle for epistemic control; for critical thinking; for evaluation to first principles; the applied use of deductive reasoning; politics; economics; tension between careerism, and the Precautionary Principle. Many in ID/PH have fought against engineering measures, but now are giving up on fighting the virus at all. It’s important to not give into the temptation of accepting that “We just have to live with it,” or that “It’s endemic now” – or “It's mild” . No . Not acceptable. COVID-19 is airborne. It’s very manageable. Wear an N95 [FFP2 respirator] in occupied spaces until case counts are near zero. Make indoor air safe – ventilate, filter it, and use UV. Set national and international standards for safe indoor air. Set a goal of elimination – first regional, then national, and then global. ❂ © 2021 Barry Hunt . ➲

❦ — “It’s in the hamsters.” (Kills hamsters.) — “It’s in the mink.” (Kills mink.) — “It’s in the white-tailed deer.” (Kills white-tailed deer.) — “It’s in the tigers, cheetahs and cats.” (Kills the tigers, cheetahs and cats.) — “It’s in the dogs.” (Kills dogs.) — “It’s in the Great Apes and monkeys.” (Kills Great Apes and monkeys.) — “It’s in the people.” (North, South, East or West first?) © 2021 C19.Life. ❂ “If you are wondering why epidemiologists are Eeyore-ing over all of the COVID-19 infections among various animals, one reason is that we currently do not have the tools to eradicate a disease with an animal reservoir. Mask up. Vax up.” Dr. Elizabeth Jacobs (14 Nov 2021)

❦ ‘There is robust evidence supporting the airborne transmission of many respiratory viruses , including measles virus, influenza virus, respiratory syncytial virus ( RSV ), human rhinovirus ( hRV ), adenovirus , enterovirus , severe acute respiratory syndrome coronavirus ( SARS [-CoV-1] ), Middle East respiratory syndrome coronavirus ( MERS-CoV ), and SARS-CoV-2 . A growing body of research on COVID-19 provides abundant evidence for the predominance of airborne transmission of SARS-CoV-2 . This route dominates under certain environmental conditions, particularly indoor environments that are poorly ventilated , an observation that implicates solely aerosols because only aerosols – and not large droplets or surfaces – are affected by ventilation. Additional precautionary measures must be implemented for mitigating aerosol transmission at both short and long ranges , with a major focus on ventilation , airflows , air filtration , UV disinfection , and mask fit . Transmission of SARS-CoV-2 has occurred in healthcare settings despite medical [blue surgical/FRSM] masks (designed for droplets not aerosols) and eye protection, which illustrates the need for proper personal protective equipment ( PPE ) and layering multiple interventions against airborne transmission, especially in high-risk indoor settings . Implementing effective ventilation systems reduces airborne transmission of infectious virus-laden aerosols. Strategies such as ensuring sufficient ventilation rates and avoiding recirculation are advised. Carbon dioxide sensors can be used as indicators of the build-up of exhaled air and serve as a simple way to monitor and optimize ventilation . Aerosol sensors can also be used to assess HEPA and HVAC aerosol filtration efficiencies, which are key to lowering infections caused by virus-laden aerosols. Assuring a minimum ventilation rate of 4 to 6 air changes per hour ( ACH ) and maintaining carbon dioxide levels below 700 to 800 ppm have been advised, although the ventilation type and airflow direction and pattern should also be taken into account. Increasing the efficiency of air filtration in HVAC systems , stand-alone HEPA purifiers , or implementing upper room UV disinfection systems can further reduce the concentrations of virus-laden aerosols. These interventions are critical strategies for helping end the current pandemic and preventing future outbreaks. The risk of outdoor transmission may rise with increased lifetime and transmissibility of viruses, such as certain variants of SARS-CoV-2. Aerosolization of virus-containing wastewater and hospital fecal discharges also poses potential outdoor exposure risks , which should not be underestimated.’ ❂ 📖 (27 Aug 2021 ~ Science) Airborne transmission of respiratory viruses ➤ © 2021 Science .

❦ BUILDINGS PLAY A CRITICAL ROLE IN THE TRANSMISSION OF AIRBORNE INFECTIOUS DISEASES. ‘Buildings play a critical role in minimizing, or conversely exacerbating, the spread of airborne infectious diseases. COVID-19 outbreaks occur indoors, and within-room long-range transmission beyond two meters (six feet) has been well documented in conditions with no masking and low ventilation rates. However, the relationship between building systems and airborne infectious disease transmission predates SARS-CoV-2, the virus that causes COVID-19. Building-related interventions have been shown to reduce the spread of many other airborne infectious diseases, including severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), tuberculosis, measles, and influenza. Following the 2009 H1N1 influenza A pandemic, an epidemiological investigation at a boarding school in Guangzhou, China found that opening windows for outdoor air ventilation was the only control measure that had significantly protected against infection. Other research confirmed that enhanced outdoor air ventilation can reduce influenza and tuberculosis transmission in school buildings. Similarly, upper-room ultraviolet (UV) germicidal irradiation installed in Philadelphia-area schools substantially reduced measles spread during an epidemic. As of early 2021, no in situ research has evaluated the independent impact of ventilation and air cleaning for reducing the risk of COVID-19 transmission in schools. However, there are a number of studies in which enhanced ventilation was used as part of layered risk reduction strategy, resulting in the successful reduction of COVID-19 infections. For example, COVID-19 cases and mitigation strategies were tracked in schools in two cities in Missouri in December 2020. Schools that used a combination of mitigation strategies including improved outdoor air ventilation were found to have lower rates of transmission compared to the rest of the community. COVID-19 transmission among children in Baden-Württemberg, Germany was also rare in schools and childcare settings that employed mitigation strategies which included improved ventilation. Conversely, inadequate outdoor air ventilation has been explicitly implicated in several large COVID-19 outbreaks across various indoor environments. Case studies have included a choir rehearsal with poor ventilation and no masks; a meat processing facility with low air exchange rates and high rates of unfiltered recirculated air; a spin class without masks and inadequate air circulation; a bus with an air conditioning system on recirculating mode, and a restaurant with poor ventilation and an air conditioner that recirculated air through the dining room. These counterexamples demonstrate that building-level strategies, including ventilation and air cleaning, are key components of risk reduction strategies for airborne infectious diseases, including COVID-19.’ ‘Schools are chronically under-ventilated.’ ❂ 📖 (April 2021 ~ The Lancet COVID-19 Commission) The Lancet COVID‐19 Commission Task Force on Safe Work, Safe School, and Safe Travel. Designing infectious disease resilience into school buildings through improvements to ventilation and air cleaning ➤ © 2021 The Lancet COVID-19 Commission.