Masks as Protection from Infection
This is a page of notes.
N95 Masks
https://nymag.com/strategist/article/whats-the-difference-between-kn95-and-kf94-masks.html
Masks-for-all for COVID-19 not based on sound data by Lisa M Brosseau and Margaret Sietsema, Apr 01, 2020.
The authors and CIDRAP have received requests in recent weeks to remove this article from the CIDRAP website....
We can see how free speech and a free speech are hated by intellectuals nowadays. They believe alternative points of view should be suppressed, as dangerous to health.
The guidelines from the Centers for Disease Control and Prevention (CDC) for face coverings initially did not have any citations for studies of cloth material efficiency or fit, but some references have been added since the guidelines were first posted. We reviewed these and found that many employ very crude, non-standardized methods (Anfinrud 2020, Davies 2013, Konda 2020, Aydin 2020, Ma 2020) or are not relevant to cloth face coverings because they evaluate respirators or surgical masks (Leung 2020, Johnson 2009, Green 2012).
The CDC failed to reference the National Academies of Sciences Rapid Expert Consultation on the Effectiveness of Fabric Masks for the COVID-19 Pandemic (NAS 2020), which concludes, “The evidence from…laboratory filtration studies suggests that such fabric masks may reduce the transmission of larger respiratory droplets. There is little evidence regarding the transmission of small aerosolized particulates of the size potentially exhaled by asymptomatic or presymptomatic individuals with COVID-19.” As well, the CDC neglected to mention a well-done study of cloth material filter performance by Rengasamy et al (2014), which we reviewed in our article.
Mask Facts, AAPS, extracts without indication here:
A COVID-19 (SARS-CoV-2) particle is 0.125 micrometers/microns (µm); influenza virus size is 0.08 – 0.12 µm; a human hair is about 150 µm.
Larger respiratory droplets (>5 µm) remain in the air for only a short time and travel only short distances, generally <1 meter. They fall to the ground quickly. Small (<5 µm) aerosolized droplets can remain in the air for at least 3 hours and travel long distances (up to 27 ft.). Since 1961, experiments showed that viral-pathogen-carrying droplets were inactivated within shorter and shorter times as ambient humidity was increased. Dryness drives the small aerosol particles.HEPA (high efficiency particulate air) filters are 99.97 to 100% efficient. HEPA filters are tested with particles that are 0.125 µm (the size of SARS-CoV-2). Surgical masks are loose-fitting devices that were designed to be worn by medical personnel to protect accidental contamination of patient wounds, and to protect the wearer against splashes or sprays of bodily fluids. They aren’t effective at blocking particles smaller than 100 µm.
N95 filtering facepiece respirators (FFRs) are constructed from electret (a dielectric material that has a quasi-permanent electric charge.) An electret generates internal and external electric fields so the filter material has electrostatic attraction for additional collection of all particle sizes. As flow increases, particles will be collected less efficiently.
All the cloth masks and materials had near zero efficiency at 0.3 µm, a particle size that easily penetrates into the lung (SARS-CoV-2 is 0.125 µm) Efficiency for the entire range of particles T-shirts — 10% Scarves — 10% to 20% Cloth masks — 10% to 30% Sweatshirts — 20% to 40% Towels — 40%
[Study measuring filter efficiency (2014, Korea) https://aaqr.org/articles/aaqr-13-06-oa-0201] Evaluated 44 masks, respirators, and other materials with similar methods and small aerosols (0.08 and 0.22 µm) N95 FFR filter — >95% efficiency Medical masks — 55% efficiency General (cloth) masks — 38% efficiency Handkerchiefs — 2% (one layer) to 13% (four layers) efficiency.
The cloth that serves as the filtration for the mask is meant to trap particles being breathed in and out. But it also serves as a barrier to air movement because it forces the air to take the path of least resistance, resulting in the aerosols going in and out at the sides of the mask.
A study of 4 patients (July 2020, South Korea). Known patients infected with SARS-CoV-2 wore masks and coughed into a Petrie dish. “Both surgical and cotton masks seem to be ineffective in preventing the dissemination of SARS–CoV-2 from the coughs of patients with COVID-19 to the environment and external mask surface.”
Studied different types of face coverings in non-clinical setting (August 2020). They used a black box, a laser, and a camera. A person wears a face mask and speaks into the direction of an expanded laser beam inside a dark enclosure. Droplets that propagate through the laser beam scatter light, which is recorded with a camera. A simple computer algorithm then counts the droplets seen in the video. The N95 led to a droplet transmission of below 0.1%. Cotton and polypropylene masks, some of which were made from apron material showed a droplet transmission ranging from 10% to 40%. Knitted mask had up to 60% droplet transmission. Neck fleece had 110% droplet transmission (10% higher than not wearing a mask). Speaking through some masks (particularly the neck fleece, bandanas) seemed to disperse the largest droplets into a multitude of smaller droplets … which explains the apparent increase in droplet count relative to no mask in that case.
In Kansas, the 90 counties without mask mandates had lower coronavirus infection rates than the 15 counties with mask mandates. To hide this fact, the Kansas health department tried to manipulate the official statistics and data presentation.
Stanford engineers estimated that N95 masks cause a 5% to 20% reduction in O2 intake. This can cause dizziness and lightheadedness.
If lockdowns and masks had an effect on covid, they should also have an effect on the incidence of colds and other infectious diseases. Eventually, if the CDC collects that data, maybe we'll be able to see.
