❦ A comprehensive collection of review articles from 1987 to 2022 regarding airborne transmission of pathogens , curated 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 . ✾

❦ “I met a nice lady – a ward patient – yesterday who, seeing my [ FFP3 ] 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) ➤

‘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 British Medical Association (22 Dec 2023)

‘The RCN is urging healthcare employers to assess the risk posed by COVID-19 and put appropriate safeguards in place for patients and staff. WHO [has] 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; and to improve ventilation in health facilities.’ ✾ ❦ 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 equipmen t 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 healthcare 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).

❦ “Coughing into one’s sleeve while in shared air is like peeing into one’s swimsuit while in shared water.”

‘This document aims to serve as interim guidance and a regulatory reference point for the design and correctly-engineered deployment of HEPA filter devices in real-world settings with regard to effectivity and safety. It focuses on HEPA filter-based devices which can be positioned locally within a room.  The emergence of SARS-CoV-2 as a highly contagious virus has demanded new and innovative solutions to safeguard patients, staff, and visitors.’

✻ Accessed: 4 Dec 2023. ➲ Date published: 9 May 2023 . ➲ Date last updated : 2 Oct 2023 . ➲ Please note: This NHS Estates page is currently being updated and re-formatted as of 08 Jan 2026 . It will be completed by 16 Jan 2026 . ❦ Applicability ‘This NETB applies to all healthcare spaces with ventilation requirements. Objective To provide additional technical guidance and standards on the use of UVC devices for air cleaning in healthcare spaces. Status The document represents advice for consideration by all NHS bodies . It is to be read alongside Health Technical Memorandum 03-01 Specialised Ventilation for Healthcare Premises (HTM 03-01) . Executive summary Ventilation * is a key line of defence for infection control in the healthcare environment . Its design and operation are described in Health Technical Memorandum (HTM-03-01) . The current focus on ventilation has highlighted areas of high risk due to poorly performing and inadequate ventilation in hospitals and other healthcare settings due to age, condition of air handling plant, lack of maintenance, challenges with effective use of natural ventilation or other creates areas of high risk. It is therefore important to bring these facilities up to the minimum specification of current standards, particularly recognising the challenges of COVID-19 and other respiratory infections . Ultraviolet (UVC) air cleaners (also known as air scrubbers) using ultraviolet light are one option for improving and upgrading ventilation. The installation of a UVC air cleaner can reduce the risk of airborne transmission . This document has been written as an interim specification to set the basic standard required for UVC devices to be utilised in healthcare and patient related settings. This edition is primarily aimed at portable and semi fixed (wall-mounted) devices. The series will extend to in-duct and upper room devices in future iterations. Devices relying on HEPA filters or similar filter-based technology can have similar benefits to UVC devices but are not considered in this document. The potential of air scrubbers employing UVC or HEPA technology is the subject of a rapid review (September 2022) . * Ventilation is the process by which ‘fresh’ air (normally outdoor air) is intentionally provided to a space and stale air is removed. This may be achieved by mechanical systems using ducts and fans, or natural ventilation most commonly provided through opening windows. The local redistribution of air may also be construed as ventilation. 1. Introduction Ventilation is a critical feature in the control of airborne infection . However, the emergence of SARS-CoV-2 as a highly contagious virus has demanded new and innovative solutions to safeguard patients , staff and visitors . Health Technical Memorandum 03-01 Specialised Ventilation for Healthcare Premises (HTM-03-01) is a robust standard for ventilation of higher risk clinical spaces based on high air change rates using outdoor air to continually flush indoor spaces. The emergence of COVID-19 has shown that greater attention must be paid to the removal or deactivation of airborne pathogens in areas where ventilation rates are lower. The focus on ventilation has also highlighted areas of high risk due to poorly performing and inadequate ventilation , particularly in older hospitals and other healthcare settings such as primary care and dental, which increase risks of infection spread viz nosocomial infections . In cases, where current ventilation does not meet HTM-03-01 standards, this may be due to age, condition of air handling plant, lack of maintenance or other design or operational issues. In the case of naturally ventilated spaces, there is a reliance on staff or patients opening windows. Weather conditions, external noise and air pollution and restricted window openings for safety affect the ability to open windows and means that ventilation in some settings can fall below recommended rates. UVC air cleaners using ultraviolet light are one option for improving and upgrading ventilation. The correct installation and operation of a UVC air cleaner can effectively reduce the risk of airborne transmission. NHS trusts are under pressure to improve ventilation and are considering options including UVC air cleaning. This standard will assist trusts in selecting and implementing good quality, reliable equipment. There is substantial evidence from laboratory studies and real-world settings that UVC is an effective technology for reducing airborne pathogens within room air and HVAC systems. A number of trial ‘case studies’ have been carried out which indicate that measured levels of micro-organisms in air are greatly reduced and infection rates have decreased. These trials have also shown that UVC within HVAC systems safely allows some levels of air recirculation and can achieve substantial energy reductions compared to the normal 100% fresh air approach set out in HTM-03-01. For example, a scheme with 50% fresh air and 50% recirculated air would reduce heat demand by 50%. However, care must be taken to ensure sufficient fresh air changes are provided for the dilution of medical gases and noxious odours, and the maintenance of appropriate oxygen and carbon dioxide levels. This document aims to serve as interim guidance and regulatory reference point for the design and correctly engineered deployment of germicidal UVC devices in real-world settings with regard to effectivity and safety. 2. UVC germicidal effects There are a wide range of UVC devices which aim to inactivate microorganisms in the air and/or on surfaces. This document focuses on contained UVC devices which can be positioned locally within a room or within an HVAC duct. These devices usually require fan-assisted circulation to introduce the room air into the device, expose it to ultraviolet light and then to reintroduce the processed air into the room. Therefore, aerodynamics internal to the device together with the lamp specification determines the air and microbial particle UVC exposure time and hence the radiation dose. These devices are known as active UVC air cleaning devices . Not considered in this document are passive UVC devices, aka upper room devices, which rely on the natural air currents within rooms. An important consideration regards the flow of the air which is induced, processed and distributed by the device external to the device itself. The design and placement of the device should promote efficient air circulation in the room space and avoid short-circuiting of air circulation relative to furniture, obstructions, and occupancy. The ultraviolet-C (UVC) spectrum lies in the interval [200…280] nm. UVC irradiation as a means of microbial inactivation has been used for over 100 years in multiple sectors including medical, scientific, water disinfection, manufacturing and agricultural. UVC germicidal activity inactivates microorganisms rendering them unable to replicate. Most commonly, germicidal activity is generated by mercury ionisation lamps with the major spectral line at 254 nm wavelength. This is sometimes also known as germicidal ultraviolet (GUV) or ultraviolet germicidal irradiation (UVGI) . This standard uses the term UVC . Recent studies suggest that devices based on far-UV (222 nm wavelength) may also be effective ; however, these are not covered here. The photo-toxicity risks associated with UVC is universally recognised. The design, specification and implementation of germicidal UVC solutions currently lacks rigorous governance and the requirement for regulatory change is recognised. The purpose of this standard therefore is to establish the key criteria for successful and reliable long-term application of UVC air cleaning while avoiding the potential safety hazards and operational pitfalls, particularly when equipment is used in spaces occupied by non-technical people. 3. Applications This standard covers the types of UVC air cleaners used as standalone or in-duct units where the principal active element is UVC at the nominal wavelength of 254 nm. In rooms without natural or mechanical ventilation, or where the ventilation falls short of local requirements or regulatory advice , auxiliary devices may be deployed to enhance the effective air changes. The installation of UVC air cleaners can be considered to contribute additional ‘equivalent’ air changes (eACH). For example, a treatment room with only 2 ACH could achieve the equivalent of 10 ACH by installing a UVC unit which recirculated and cleaned the equivalent of 8 ACH (eACH) for the micro-organisms of concern. Hence, to meet the requirements that comply with HTM-03-01, the number of devices required will be dictated by the existing background levels of ventilation. In-duct HVAC systems In buildings with existing HVAC systems which have recirculation of air, it can be effective to install UVC lamps directly into the ducts, placing them downstream of pre-existing particulate filters. This allows for the treatment of all rooms in the building covered by the HVAC system or within branch ducts serving various zones and the rooms within those zones. Due to the lamps being contained within the ducts, the risk of direct exposure to UVC is low. However, maintenance can be carried out; safely shut-down interlocks should be fitted and hazard notices compliant with BS EN ISO 7010 prominently displayed. 254 nm devices covered in this standard ❂ In-duct UVC: UVC lamps are installed directly into the HVAC system or are contained within a locally installed ventilation device which is connected into the HVAC system, similar to a fan-coil unit. Devices may use the fans and filters within the existing HVAC system or, in some cases, may have local fans and filters to provide the recirculation. Significant modelling and design are required to implement such systems. ❂ Floor standing UVC ‘mobile’ devices: UVC lamps are contained within a standalone floor mounted device that can be positioned at any suitable location in a room. These devices provide local air cleaning within a room and are plugged into a standard electrical socket so do not require any installation. The device contains lamps, dust filters and a fan to draw room air through the device. Devices are portable and so can be easily moved. ❂ Fixed UVC devices – wall or ceiling mounted: Similar to floor standing units but fixed to a wall or ceiling. These devices will normally be permanently wired into the room electrical system rather than plugged into a wall socket. UVC devices not covered in this standard ❂ Decontamination UVC devices: High intensity open-field UVC devices that are designed for periodic surface decontamination in unoccupied spaces. These devices are sometimes known as UVC robots. ❂ Upper-room UVC devices: UVC devices which utilise an open UV field within the room above the heads of occupants. These are passive devices which rely on the general circulation of room air and are sometimes assisted by ceiling fans. ❂ Devices based on other parts of the UV spectrum: The devices covered in this standard are based on 254 nm wavelength lamps. There are a number of other UV technologies including Far UV (222 nm) which has early data showing it is likely to be effective. ❂ Devices that incorporate other technologies alongside UVC: There are a number of devices which use UVC alongside other technologies such as titanium dioxide catalysts or ionisers. These devices often emit by-products into the room, either intentionally or deliberately. The health impacts of any emissions must be carefully considered.’ ❂ * Additional info. Source Sans Pro Normal 21/18. 1st row, 4th Colour. ❂ 📖 (2 Oct 2023 ~ NHS England NHSEstates Technical Bulletin (NETB 2023/01B):applicationof ultraviolet (UVC) devices for air cleaning in occupied healthcare spaces: guidance and standards ➤ ✻ Accessed: 4 Dec 2023. ➲ Date published: 9 May 2023. ➲ Date last updated: 2 Oct 2023 . © 2023 NHS England.

✻ 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.’ ❂ ➲ [ Note ] : The accepted scientific definition of ‘airborne 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 .

❦ “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 ➲

❦ “The truth is that SARS2 is so contagious, so virulent, and reinfects so easily that there is no off-ramp for masking in healthcare. At least not without better vaccines and therapeutics that actually stop transmission and prevent Long Covid, Cardiovascular Covid and Neurocovid.”

❦ “Dear economy enthusiasts... The only humane way to avoid locking down for airborne disease control ever again is to set up safer indoor-air infrastructure... globally. Everyone that is slowing down this process is asking for another lockdown. Or mass murder. More likely another lockdown though because in the end, if bird flu takes off or MERS has an interesting offspring... the public will not stomach as much death as the anti-lockdown and dirty-air proponents would like.”

❦ “Since the pandemic began, I have constantly made the argument that a healthy workforce is a necessity for a healthy economy. This, to me, is the definition of obvious. The same argument applies to education. I’m writing this because I’ve received a large number of messages and e-mails this week from parents who are being placed under extreme pressure by schools in an attempt to stop their children trying to avoid infection. Let me be very, very clear: education is extraordinarily important. Health is extraordinarily important. A child’s education will suffer if that child is unwell. Again, the definition of obvious. Parents should not be put in a position in which they are being forced to choose between their child’s health and their child’s education. It is a false dichotomy that mirrors the pernicious culture of presenteeism that is sadly still present in many workplaces. It’s also driven by the nature of box-ticking bureaucracies that always seek to maintain the status quo. This is both an ethical and pragmatic argument. Ethical, because placing pressure on parents to have to choose between access to education and near-certain infection of their children is morally wrong. And, believe me, I make moral statements carefully. Pragmatic, because if schools simply introduced air-filtration as standard, and encouraged parents to keep children with acute Covid off school, there would be far, far less transmission in schools – thus improving the quality of education for all. Again, the definition of obvious. Much like the economy, we need to employ medium- and long-term thinking now, rather than short-term thinking that clings to the status quo purely for its own sake. And remember, reduction of transmission in schools reduces transmission in the wider community. As such, this means that less adults are sick at any given time, which is also good for the economy. This is so clear that it baffles me that most policy-makers seem to fail to understand it.” © 2023 Conor Browne . ➲

❦ “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 ➤

❦ Medical school lectures on respiratory pathogens in 2060: “Interestingly in the 1900s and early 2000s, doctors thought respiratory viruses were transmitted by fomites, not aerosols. They spent a tremendous amount of energy cleaning hands and surfaces instead of cleaning indoor air. Unsurprisingly, they were quite terrible at limiting the spread of respiratory viruses and had terrible epidemics each year leading to thousands of deaths, including many among infants and young children.” “Air hygiene has been one of the greatest public health advancements of the century.”

Ryan Hisner pulls apart the real-life Animal Farm theatre playing out between Man, Pig and The Economy in his 2022 essay on swine, clean air, and bringing home the bacon. ✾ ❦ “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 . ➲

❦ ‘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 .

❦ from ‘The Lancet COVID-19 Commission Task Force on Safe Work, Safe School, and Safe Travel’ : ‘Buildings play a critical role in minimizing, or conversely exacerbating, the spread 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.’ ✾ ‘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 .