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With the outbreak of COVID-19 Cassbeth began research on the disaster from a systems perspective and quickly focused on ventilation. The research is found here. Return to Life. The IP is found here: Airborne Contagion Assessment Ventilation Alarms System.

The Cassbeth analysis showed that the problem is massive within small enclosed spaces, problematic in large spaces, and extremely rare in outdoor spaces. It was also found that the technology exists, is relatively low cost, and is part of the system solution in elite settings. The problem is a social problem where the technology and system solutions must find their way into all facilities especially schools, airports, airplanes, bars, restaurants, etc. where large numbers of people congregate and where the facilities are not properly maintained or operated.

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This system was inspired by:

A Paradigm Shift to Combat Indoor Respiratory Infection

In May of 2021, 39 scientists published "A Paradigm Shift to Combat Indoor Respiratory Infection" calling for a paradigm shift in how citizens and government officials think about the quality of the air we breathe indoors. At some point in history this document will be referenced for decades.


There is great disparity in the way we think about and address different sources of environmental infection. Governments have for decades promulgated a large amount of legislation and invested heavily in food safety, sanitation, and drinking water for public health purposes. By contrast, airborne pathogens and respiratory infections, whether seasonal influenza or COVID-19, are addressed fairly weakly, if at all, in terms of regulations, standards, and building design and operation, pertaining to the air we breathe. We suggest that the rapid growth in our understanding of the mechanisms behind respiratory infection transmission should drive a paradigm shift in how we view and address the transmission of respiratory infections to protect against unnecessary suffering and economic losses. It starts with a recognition that preventing respiratory infection, like reducing waterborne or foodborne disease, is a tractable problem.

The following are key extracts from the paper, A Paradigm Shift to Combat Indoor Respiratory Infection.

There is great disparity in the way we think about and address different sources of environmental infection. Governments have for decades promulgated a large amount of legislation and invested heavily in food safety, sanitation, and drinking water for public health purposes. By contrast, airborne pathogens and respiratory infections, whether seasonal influenza or COVID-19, are addressed fairly weakly, if at all, in terms of regulations, standards, and building design and operation, pertaining to the air we breathe.

Most modern building construction has occurred subsequent to a decline in the belief that airborne pathogens are important. Therefore, the design and construction of modern buildings make few if any modifications for this airborne risk (other than for specialized medical, research, or manufacturing facilities, for example). Respiratory outbreaks have been repeatedly “explained away” by invoking droplet transmission or inadequate hand hygiene.

For decades, the focus of architects and building engineers was on thermal comfort, odor control, perceived air quality, initial investment cost, energy use, and other performance issues, whereas infection control was neglected. This could in part be based on the lack of perceived risk or on the assumption that there are more important ways to control infectious disease, despite ample evidence that healthy indoor environments with a substantially reduced pathogen count are essential for public health.

It is now known that respiratory infections are caused by pathogens emitted through the nose or mouth of an infected person and transported to a susceptible host.

Although the highest exposure for an individual is when they are in close proximity, community outbreaks for COVID-19 infection in particular most frequently occur at larger distances through inhalation of airborne virus laden particles in indoor spaces shared with infected individuals

There are ventilation guidelines, standards, and regulations to which architects and building engineers must adhere.

None of the documents provide recommendations or standards for mitigating bacteria or viruses in indoor air, originating from human respiratory activities. Therefore, it is necessary to reconsider the objective of ventilation to also address air pollutants linked to health effects and airborne pathogens.

There needs to be a shift in the perception that we cannot afford the cost of control, because economic costs of infections can be massive and may exceed initial infrastructure costs to contain them. The global monthly harm from COVID-19 has been conservatively assessed at $1 trillion ([internal ref]), but there are massive costs of common respiratory infections as well. In the United States alone, the yearly cost (direct and indirect) of influenza has been calculated at $11.2 billion; for respiratory infections other than influenza, the yearly cost stood at $40 billion.

We encourage several critical steps. First and foremost, the continuous global hazard of airborne respiratory infection must be recognized so the risk can be controlled. This has not yet been universally accepted, despite strong evidence to support it and no convincing evidence to refute it.

Comprehensive ventilation standards must be developed by professional engineering bodies. Organizations such as the American Society of Heating, Refrigerating and Air-Conditioning Engineers and the Federation of European Heating, Ventilation and Air Conditioning Associations have ventilation standards, and during the COVID-19 pandemic, they have proposed building and system-related control actions and design improvements to mitigate risk of infection. However, standards must be improved to explicitly consider infection control in their statements of purpose and definitions. New approaches must be developed to encourage implementation of standards (e.g., “ventilation certificates” similar to those that exist for food hygiene certification for restaurants).

The COVID-19 pandemic has revealed how unprepared the world was to respond to it, despite the knowledge gained from past pandemics. A paradigm shift is needed on the scale that occurred when Chadwick’s Sanitary Report in 1842 led the British government to encourage cities to organize clean water supplies and centralized sewage systems. In the 21st century, we need to establish the foundations to ensure that the air in our buildings is clean with a substantially reduced pathogen count, contributing to the building occupants’ health, just as we expect for the water coming out of our taps.

.The City of Philadelphia

Healthy Infrastructure - Philadelphia Water Works

The Philadelphia Water Works was the first water treatment facility in the United States built between 1812 and 1872, it operated until 1909. It was a model for all future water works to follow in the New World. People would flock from around the planet to see this facility which combined engineering and art to solve a massive problem of safe water for the inhabitants of Philadelphia. It was born of necessity as the people decided they would not tolerate yet another yellow fever outbreak. The Museum sits on top of the original water reservoir that provided the city with water. As Philadelphia grew the reservoir and Water Works could no longer meet the needs of the city and new projects eventually replaced this once great technological and artistic achievement. It stopped operations in 1909.

The Philadelphia Art Museum and Water Works

A post vaccine world implies that everyone has received a vaccine against the COVID-19 virus. However, we know that will not happen. In the USA some will refuse the vaccine. In many countries the poor will not have access to the vaccine. The idea of a post vaccine world also suggests that we can return to the pre-COVID world. However, we know that is not the case. The contagion and its variants will be in the environment for decades. This is not unlike the situation that existed in the early part of the last century where there were deadly contagions that were part of normal life. It was not until multiple technologies were introduced in multiple systems that there was a decline in many deadly contagions in the USA and other parts of the world. These technologies and systems were embedded in:

Philadelphia Restaurant Program

In the wake of the COVID-19 disaster the city of Philadelphia has once again taken lead actions like the Enhanced Ventilation Standards for Indoor Dining and Application Form for Increased Dining Capacity dated February 14, 2021. The Enhanced Ventilation Standard calls for 15 air changes per hour (ACH) for establishments wanting to double their seating capacity. The approach is brilliant and uses the incentive to increase income to offset any possible costs that may be needed to increase ventilation. The ventilation level increase is large and will significantly mitigate contagion levels in the restaurant. It is obvious that it is traceable to existing engineering requirements associated with contagions rather than subjective minimum comfort levels. As part of the initiative they posted how to videos:

https://www.youtube.com/watch?v=HlneLDi9r54 (video on how to calculate air changes per hour)
https://www.youtube.com/watch?v=58uRfAxh6Cw (video on how to complete the application)

These people are brilliant. The city of Philadelphia is leading the world on how to deal with the COVID-19 disaster for indoor settings. Unfortunately this program stopped in May 2021 leaving a void in this very important area of ensuring public buildings have ventilation levels that mitigate contagions rather than just provide minimum comfort levels. However, the model exists along with the recommended ACH level.

Philadelphia School Ventilation Disclosure

The city of Philadelphia has also taken the time and effort to understand their school facilities and they have performed an extensive site survey (air balance reports) of all their school. The school district has 240+ schools and 12,000+ rooms. They made this critical information public via their website. Once again Philadelphia has taken a lead in trying to deal with another aspect of the COVID-19 disaster and that is to understand the current state of the schools and share the data with the Philadelphia taxpayers and people everywhere.

Fresh Air Movement From The Last Century

Before the introduction of antibiotics in the 1940s many infectious diseases such as Tuberculosis were treated using a fresh air cure. Tuberculosis spreads from person to person via coughing, sneezing and spitting. Tuberculosis usually affects the lungs. Left untreated, up to two thirds of those infected with Tuberculosis will die. Starting in the 19th century, Tuberculosis patients were forcibly isolated in sanatoriums built in remote locations all around the world, including Australia, where they were provided with the top treatment of the day: fresh air and sunlight.

Dr. Auguste Rollier had a substantial cure rate for tuberculosis by exposure to sunlight, or heliotherapy. His students are pictured here working outside in 1925.

Fresh air treatment was accepted and practiced in all types of settings including special treatment sanatoriums and hospitals.

Fresh Air treatment for TB sufferers in London 1936

1937 New Ventilation Technology Study

A key study was performed in Philadelphia by W.F. Wells on the use of a new technology - Ceiling Level UV lights. He was an Associate Professor in Research in Airborne Infection at the Laboratories for the Study of Airborne Infection in the Department of Preventive Medicine and Public Health at University of Pennsylvania School of Medicine, Philadelphia, PA. The findings were presented in part before the Engineering Section of the American Public Health Association at the Seventy-first Annual Meeting at St. Louis, Mo., October 30,1942. It was supported by a grant from the Common wealth Fund to the University of Pennsylvania for the study of the mechanics of airborne infection and control. The design was based on science and engineering using numbers to understand the system and its level of performance.

Swarthmore Public School Classroom circa 1937 - 1943

The rest is history. The history is of a people who knew about the need to address airborne infections. They provided us with modern forced air Heating Ventilation and Cooling (HVAC) systems and Ceiling Level UV-C systems to clean the air in buildings so that they approach what is found outside in the fresh air. They built upon the fresh air movement. Today this generation must rise to the occasion and deal with fresh air in all our buildings using the tools of their time - social media, Internet, smartphones, computers, etc.

Is your faculty ventilation turned on? If not why?

Do you know its performance level in terms of Air Changes per Hour (ACH)? If not why not?

Do you care? If not why not?



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