“Sewing a Covid-19 Mask? You Need This Chart”
“The popularity of homemade face masks has soared as authorities simultaneously exhort the public to take precautions against Covid-19 infection and demand that scarce medical-grade equipment be saved for health-care professionals.
Research published in the journal Disaster Medicine and Public Health Preparedness demonstrates that a number of factors coalesce to make a face mask effective — including proper fitting, cleaning and disposal, and the inevitable trade-off between filtration efficiency and the effort required to breathe.
The authors note that “any mask, no matter how efficient at filtration or how good the seal, will have minimal effect if it is not used in conjunction with other preventative measures, such as isolation of infected cases, immunization, good respiratory etiquette, and regular hand hygiene.” And they conclude: “a homemade mask should only be considered as a last resort to prevent droplet transmission from infected individuals, but it would be better than no protection.”
The chart below illustrates the efficiency of various domestic fabrics against Bacillus atrophaeus, “a rod-shaped spore-forming bacterium [0.95-1.25 μm] known to survive the stresses caused by aerosolization,” which was chosen by the researchers to simulate an influenza virus.”