The Case for HEPA Air Filtration
Written by: Josh Pascoe
After many months, the World Health Organization (WHO) is finally acknowledging the likelihood that COVID-19 is spread in the air - after more than 200 scientists from across the globe urged the agency to do so.
In an open letter published in a journal in mid-July, two scientists from Australia and the U.S. wrote that studies have shown "beyond any reasonable doubt that viruses are released during exhalation, talking and coughing in microdroplets small enough to remain aloft in the air."
The two researchers, along with more than 200 others, appealed for national and international authorities, including WHO, to adopt more stringent protective measures. “Airborne spread, particularly in specific indoor locations such as crowded and inadequately ventilated spaces cannot continue to be ruled out" WHO said.
In the following paragraphs, we’ll explore what is currently being done to prevent transmission of COVID-19 and what can be included as part of a multi-layered strategy to help mitigate the newly validated airborne transmission risk of COVID-19.
The current guidance from numerous international and national bodies is focused on hand washing, disinfecting high-touch surfaces and maintaining physical distancing where possible, as well as mask use in public or crowded situations. Until now, most public health organizations, including the WHO, do not recognize airborne transmission except for aerosol-generating procedures (AGPs) performed in healthcare settings, particularly in dental practices. Hand washing and physical distancing are appropriate, however, alone they are insufficient to provide protection from virus-carrying respiratory droplets released into the air by infected people. This problem is especially acute in indoor or enclosed environments, particularly those that are crowded and have inadequate ventilation. Common examples of impacted environments include gyms, restaurants, our children’s classrooms, call centres and other multi-cubicle workplaces. As we have entered the next phase of re-opening across Ontario, there is concern that this transmission route is being overlooked, particularly as we begin to see more crowding in indoor areas.
In addition to the current preventative measures, there is another consideration that is recognized by the medical community in Canada. In the “Infection Control Management of Novel Respiratory Infections” guidelines released by Public Health Ontario the “Inpatient Accommodation” recommendations include the use of a portable HEPA filtration unit (3.4.2) as a transmission mitigation measure highlighting the fact that COVID-19 is airborne and can be removed from the air using the proper equipment.
HEPA air filtration is so effective that its filtration performance was studied by NASA in 2016 in the white paper titled “Submicron and Nanoparticulate Matter Removal by HEPA-Rated Media Filters and Packed Beds of Granular Materials”. The study concluded that “the phenomena associated with particulate matter removal by HEPA media filters and packed beds of granular material (the same filter combination used in Austin Air’s products) have been reviewed relative to their efficacy for removing fine (<2.5 μm) and ultrafine (<0.01μm, defined as nanoparticulate) sized particulate matter. Both HEPA media filters and packed beds of granular material, such as activated carbon, which are both commonly employed for cabin atmosphere purification purposes, are found to have efficacy for removing nanoparticulate contaminants from the cabin atmosphere. When used alone, HEPA-rated media provides superior performance for removing virtually 100% of particulates.”
COVID-19 coronavirus is found to average 0.125 microns in size, but when coupled with a respiratory droplet increases to 5-10 microns in size and is well within the 99.97% efficacy filtration spectrum of medical grade HEPA allowing COVID-19 to be filtered from the air.
Implementing HEPA air filtration
Implementing HEPA air filtration involves a two-fold approach in the battle against COVID. The most obvious use for the product is its ability to directly remove COVID-19 from the air by filtering it and lowering the viral load. The second and less obvious benefit is the filtration medium’s primary use in filtering fine particulate matter from the air which includes dust, allergens, dander and other microparticulate.
Once airborne, COVID-19 positive nuclei droplets can easily attach to fine particulate matter in the air. A study from the University of Science and Technology of China reinforced this idea and stated that “Our study suggests that there is a statistically significant relationship between air pollution and COVID-19 infection. Short-term exposure to higher concentrations of PM2.5, PM10, CO, NO2 and O3 is associated with an increased risk of COVID-19 infection.” The correlated relationship enables the infected droplets to remain airborne for hours and sharply increases the viral transmission risk. By cleaning the air of both airborne droplets and fine particulate matter, we can drastically reduce the coronavirus’ ability to remain airborne and successfully mitigate the airborne transmission risk.
Medical grade HEPA air filtration is a very powerful tool that can be utilized quickly and cost-effectively. In early July, Governor Cuomo of New York State made it mandatory for large indoor public spaces to have HEPA air filtration systems that can filter COVID droplets and aerosols installed. Some post-secondary institutions, including Portland State and Penn State University, have attempted to install high efficiency filters (MERV-13+) in their buildings HVAC systems to help mitigate the airborne transmission risk. While their intentions are good, HEPA filters are not easily adapted to a building’s HVAC, as noted by Richard Corsi, Dean of Maseeh College of Engineering & Computer Science and the air quality expert at Portland State University, since the system was initially designed for heating and cooling and not microparticulate removal. “What we’re trying to do is recommend things that can be implemented in the short term,” said William Bahnfleth, Professor of Architectural Engineering at Penn State, in an interview with The Washington Post. “If every building had to have its HVAC system overhauled, that just wouldn’t be feasible.” The natural solution would then be to focus on medical-grade portable HEPA air filtration systems. These units are easily implemented in any setting where a standard 110V power outlet is available and the machines are often on casters so that they can be rolled and moved if needed.
An additional benefit that HEPA air filtration systems provide is clean air for people who cannot wear a mask due to respiratory issues or may have trouble physically distancing. This group of people often includes the elderly and young children. Our school boards would be wise to take note of the actions governments and large organizations are taking south of the border in the United States as we draw closer to September and toward the eventual reopening of our province’s schools. HEPA air filtration will help to add an additional layer of comfort and security for both teachers and students knowing that the airborne risk of COVID-19 is mitigated with the placement of a medical grade air purifier in each classroom.
In the early days of this pandemic, the world was faced with a shortage of PPE in all corners as North America was simply not prepared to supply hundreds of millions of people with medical-grade personal protective equipment, which included high-grade alcohol based hand sanitizer and N95 face masks. Often, masks needed to be imported from overseas which caused lengthy delays and increased the local market price of those goods, prompting local governments to call-out and fine companies for price gouging.
There are far fewer manufactures of medical-grade HEPA air purifiers than there are PPE manufacturers worldwide. In fact, there is only one manufacturer in all of North America that has kept manufacturing entirely in-house at their 480,000 square foot plant in Buffalo, New York.
Those who are considering implementing HEPA air filtration within their organization need to keep this fact in mind as an eventual supply shortage of air purifiers and a repeat of what occurred with PPE worldwide is possible and very likely to occur.
In summary, HEPA air filtration is an easily accessible, cost-effective and adaptable technology that, given what we now know about COVID-19’s airborne transmission route and risk, should be implemented in large public spaces across Ontario. HEPA helps lower the viral load by removing not only COVID laced respiratory droplets but also the fine particulate matter that helps it stay airborne for long periods of time. The technology is also an asset to those who are vulnerable and unable to wear a mask for medical or disability reasons. As an additional preventative measure, and part of a multi-layered strategy that includes physical distancing, hand-washing and face masks, HEPA air filtration must be considered as a vital component to helping prevent airborne transmission and to assist in safely reopening our province.
Association between short-term exposure to air pollution and COVID-19 infection: Evidence from China: https://www.sciencedirect.com/science/article/pii/S004896972032221X
It is Time to Address Airborne Transmission of COVID-19: https://academic.oup.com/cid/article/doi/10.1093/cid/ciaa939/5867798
As America struggles to reopen schools and offices, how to clean coronavirus from the air: https://www.washingtonpost.com/climate-environment/2020/06/26/coronavirus-indoor-air-school s-offices/?arc404=true
Submicron and Nanoparticulate Matter Removal by HEPA-Rated Media Filters and Packed Beds of Granular Materials: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170005166.pdf
Ontario Public Health: Best Practices for Prevention, Surveillance and Infection Control Management of Novel Respiratory Infections in All Health Care Settings: https://www.publichealthontario.ca/-/media/documents/B/2020/bp-novel-respiratory-infections.pd f?la=en
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