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upamfva     Joined: 05 May 2021   Posts: 727  
Post Posted: 2021-10-30 04:30
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Mask type really matters

A recent study out of Canada shows wide disparities in the effectiveness of different types of masks and suggests ventilation improvements can do better than common cloth and surgical masks in reducing transmission of COVID-19.To get more news about dustproof mask factory outlet , you can visit official website.

University of Waterloo researchers used a sealed room, a masked mannequin and atomized olive oil to simulate breathing in their study. They used lasers to measure the aerosols, tiny particles that can float in the air, getting past masks and circulating in the room.

Then they added ventilation, courtesy of an air purifier equipped with the sort of high-powered HEPA filters used in labs and on airplanes.

Though the virus behind COVID-19 is present in larger droplets, which all masks help block, it's also thought to transmit through these much smaller aerosols. In fact a separate study released last week suggests airborne/aerosol transmission may be the dominant form of transmission.N95 masks and similar masks filter exhaled air much better than cloth and surgical masks. Cloth and surgical masks caught 10 to 12 percent of aerosols breathed out in the experiment. Various N95, KN95 and R95 masks stopped 46 to 60 percent.
Even N95 masks leak, primarily around the nose, allowing aerosols to circulate. This led to "notably higher" concentrations of aerosols more than six feet away from the mannequin.
N95 masks with valves lost half their ability to stop aerosols. N95's without valves remain the recommended choice, "if worn correctly," but a loose-fitting N95 "provides a negligible" filtration efficiency.
The study found "increased ventilation/air-cleaning capacity significantly reduces the transmission risk in an indoor environment, surpassing the apparent mask filtration efficacy." The university put that another way in a press release on the study: "Even modest ventilation rates were found to be as effective as the best masks in reducing the risk of transmission."
"Indeed, our research shows that fresh air exchange or air purification can be very effective in controlling aerosol buildup indoors," Professor Serhiy Yarusevych, one of the researchers, told WRAL News via email. "The most beneficial strategy would be to employ both masks and ventilation to minimize the risk of virus transmission. However, given the relatively low efficiency of cloth and surgical masks in aerosol control, it is essential to complement their use by adequate ventilation for prolonged indoor occupancy."

WRAL News shared this study with four experts here in North Carolina: A virologist, an epidemiologist, a chemist who previously tested masks in his own experiments and a mechanical engineer who studies fluid dynamics.

"This paper confirms with a more controlled set-up (and more math) what other studies have shown before," said Dirk Dittmer, director of virology and global oncology programs at the UNC Lineberger Comprehensive Cancer Center. "N95 is much better than anything else."

Dittmer said that, in Germany, the government routinely sends his parents and others N95 masks. He also said ventilation is important, along with mask fit. Because he works in a lab with coronaviruses, Dittmer said he gets annual fitting lessons.Pia MacDonald, a UNC professor of epidemiology and senior director of applied health research for RTI International, said ventilation should be considered crucial.

"While masking is one strategy for reducing risk of transmission indoors, the combination with ventilation (air exchange) is a critical strategy to reducing risk of SARS-CoV-2 transmission," she said.Tarek Echekki, a professor of mechanical and aerospace engineering at N.C. State, noted that the Waterloo study had an average droplet size of one micron.

"A human exhalation may involve larger droplets as well," he said. "It is not clear if the use of smaller droplets is placing the more common face masks (surgical and cloth) at a disadvantage and thus reducing their efficacy."

Echekki noted that the study doesn't account for any protection you get for your self in wearing a mask, it only measures aerosols exhaled. He said the experiment deviates from normal life in a number of ways, but he called it "a nice addition to the available literature."

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