How to Clean Our Indoor Air Properly Against COVID-19
From UV to ionization, a leading expert explains the best technologies for indoor air disinfection to reduce COVID-19 transmission.
Early in the pandemic, aerosol spread of COVID-19 was considered less important than other transmission pathways. But it is now clear that vast majority of its spread is the result of inhaled aerosol, with a lesser amount attributable to direct contact with droplets.
The Importance of Air Filtration
Presented with particulate air contamination, a standard engineering response is to filter the air. High-efficiency air filters can be used in building ventilation systems to assure that fewer than 99.9% of respirable-size particles are recirculated back into rooms, essentially converting recirculated air into the equivalent of infection-free outdoor air. While some filter manufacturers boast of inactivating virus with UV, bipolar ions, cold plasma, or other technologies as advantageous over simple retention, there is no practical difference for risk in rooms. Importantly, while environmentally adapted TB bacteria and fungal spores readily spread through ventilation ducts, and this is theoretically possible for SARS-CoV-2 virus, there are few if any convincing reports of COVID-19 spread from room-to-room or floor-to-floor exclusively through ventilation systems – a relevant exception being a single report of spread of waste-water contaminated air not through ventilation ducts, but through faulty plumbing stacks in a high-rise apartment building in China.
Far UV refers to 222 nm UV that has the remarkable properties of being equally or more effective against airborne viruses and bacteria, but unable to penetrate even the thin liquid layer covering the surface of the eye, or the outermost layers of skin. While conventional upper room UV has long been safely used to disinfect air in occupied rooms, Far UV appears safer yet with little potential for even mild eye or skin irritation when used within established exposure guidelines. It does not reach the deeper layer of skin cells where solar UV can cause skin cancer. Far UV sources require effective filters to prevent exposure to unwanted longer-wavelength UV that can be damaging. Applications of current Far UV fixtures might include treating air and counters between workers and clients, such as bars, salons, restaurant tables, elevators, other high contact settings. Far UV is currently being used, for example, in a Boston homeless shelter, a Boston nightclub and piano bar, and for some critical U.S. military applications.
GUV raises safety concerns primarily because of a public perception that it is the same as the UV in sunlight. But not all UV is the same. It is skin exposure to the more tissue-penetrating longer wavelength UV in sunlight (UV-A and UV-B radiation) that is associated with skin cancer, and eye exposure to sunlight with cataracts, whereas shorter wavelength GUV penetrates eyes and skin surfaces far less, not reaching the lens of the eye to cause cataracts, or the deep layers of skin where it could induce cancer within well-established exposure limits. As mentioned, Far UV is far less penetrating and safe for direct exposure of room occupants. Acceptance and wider deployment of safe and highly effective UV systems will require education—of professional engineers, architects, and safety personnel, as well as the general public.
Nearly two years into the COVID-19 pandemic, the post-pandemic world is becoming clearer. While vaccines remain the mainstay of controlling person to person aerosol transmission, the efficacy of social distancing and mask wearing has been proven scientifically, albeit not fully accepted or implemented. Since the vast majority of COVID-19 likely spreads indoors, air disinfection is an underutilized role making indoor living safer. Building ventilation, natural and mechanical, is vitally important for the health and comfort of occupants. At its best, natural ventilation can be highly effective in reducing the risk of aerosol born infection, but it is not feasible or reliable in many climates and buildings. Mechanical ventilation is designed for comfort, not infection control, and generally in most buildings cannot achieve the air change rates needed to protect against a highly infectious viral aerosol like the current COVID-19 variants.
It’s clear that for indoor spaces air disinfection is a safe and efficient way to reduce transmission. Although they are not equivalent, the three established and proven air disinfection technologies are mechanical ventilation, upper room GUV, and portable room air cleaners. Of these, upper room UV is the most cost-effective and is demonstrably safe and readily available to deploy today to reduce COVID-19 and other respiratory virus transmission. Far UV is available, even safer, and may be a more effective air disinfection technology because it works around room occupants and does not depend on room air mixing. Although limited by the ability to quietly move sufficient air in many rooms, room air cleaners also have a role for in-room air disinfection, especially in small rooms where at least 6 equivalent air changes per hour can be achieved. Implementation of effective air disinfection, while driven by the COVID-19 pandemic, should find its way into building codes and practices so that we are not as unprepared for seasonal respiratory viruses, ongoing epidemics like TB, and the next pandemic.
The above excerpts are part of the Times, for more details：
My Lumens Artemis Far UVC Disinfection Devices are equipped with Care222 modules(filtered far uvc 222nm technology) developed by Ushio,Japan.
Countinuously disinfecting in occupied space, but harmless to skin and eyes of human.
Care for you, Safe for you, and Protect you!