Recent studies have shown that COVID-19 is not transmitted just by droplets but also by aerosols. (eg Twang et al, 2021 and Samet et 2021. Aerosols can disperse as far as 10m (33 feet). Thats about the size of a small waiting room or small office. (WHO dragged its foot about accepting aerosol transmission of COVID-19 and cost many deaths.)
For aerosol sterilization, proper ventilation and air that is not re circulated would reduce transmission. For space that is not properly ventilated, such as air conditioned rooms an option is sterilization by UV radiation. Sterilization by UV is now not very expensive, and commonly available home and house supply stores.
Waiting Room/Small Office
Air Purifiers with UV that can purify a 1,000 sq ft in one hour (or 600 sq ft in 30 minutes) is about USD 100. Not giving a link to a particular item or store, as would appear endorsement. A search for "air purifiers with UV" will give many results.
Isolation Beds
Isolation rooms maybe to expensive in numbers. A cheap alternative might isolation beds with in-going and outgoing air being UV sterilized. Basically a plastic canopy covering for the bed and adaptive plumbing to two UV air purifiers One for air into bed enclosure. The other for air to be sucked out of bed enclosure.
Important Note
Combining UVC irradiation to recirculating air filtration might enhance elimination of airborne microorganisms.
UVC irradiation (100–280 nm) is highly mutagenic for microorganisms and its efficacy is dependent oh the dose (J/m2) which is composed of
- a) UVC intensity (W/m2) and
- b) exposure time (s),
- c) the wavelength (254 nm),
- d) relative humidity (RH) and
- e) the susceptibility of microorganisms to UVC irradiation
Through the formation of thymidine dimers, UVC functions as a mutagen
and leads to damage of the microbial DNA. Several studies demonstrated
the virucidal and bactericidal effectiveness of UVC irradiation (see pig facility citation for more detail)
Some References of UV Sterilization of Air
Wai et al (2020) BMC Infectious Diseases
volume 20; 127
In the disinfection tests against seasonal influenza viruses H1N1 and H3N2, we also demonstrated that viral load could be effectively reduced by 4-log10 folds after 20 min VUV illumination and this also satisfied the criterion of valid germicidal result. Additionally, more than 3-log10 reduction in viral load can be attained with < 10 min of treatment.
Eisenhofel et al (2019) PLOS ONE, November 2019 (This was on pig facility)
Tests at laboratory scale were performed using aerosols of Staphylococcus (S.) aureus, Actinobacillus pleuropneumoniae, porcine parvovirus (PPV) and porcine reproductive and respiratory syndrome virus. We varied relative humidity (RH) to evaluate its effect on UVC irradiation efficiency. In addition, viability of pathogens inside the filter material was determined over up to six months. UVC-combined air filtration resulted in a more than 99% reduction of viral and bacterial particles. RH had no influence on UVC efficiency. Viability in the filter matter varied depending on the pathogen used and RH with S. aureus and PPV being most resistant.
Tim Sandle (2020) American Pharmaceutical Review June 2020 (does not seem peer reviewed)
Effectivity of HEPA Filters to Remove Viruses from Air Entering Cleanrooms
sereno barr-kumarakulasinghe, May 24th, 2021
Also published on
https://www.linkedin.com/pulse/covid-droplets-vs-aerosols-uv-sterilization-sereno-barr-kumar/
pdf version available
https://drive.google.com/file/d/1iORwmRm0jK75J7IU6Ft0hDbvKcgPkOiG/view?usp=sharing
==============================
All pandemic long, scientists brawled over how the virus spreads. Droplets! No, aerosols!heart of the fight was a teensy error with huge consequences.
They ticked through a growing list of superspreading events in restaurants, call centers, cruise ships, and a choir rehearsal, instances where people got sick even when they were across the room from a contagious person. The incidents contradicted the WHO’s main safety guidelines of keeping 3 to 6 feet of distance between people and frequent handwashing. If SARS-CoV-2 traveled only in large droplets that immediately fell to the ground, as the WHO was saying,
Marr was no stranger to being ignored by members of the medical establishment. Often seen as an epistemic trespasser, she was used to persevering through skepticism and outright rejection.
Well mate, I don't get what you are trying to do. Are you an anti vaxxer, a covid denier, or just a blogger who doesn't understand science? Are you anti-American because of whatever happened to you and still want to comeback to the capitalism you hate?
ReplyDelete