|CBC’s Marketplace put more than two-dozen masks through the rigorous National Institute for Occupational Safety and Health aerosol test to see how they stacked up in filtration efficiency compared to what is commonly considered the gold standard in protecting health-care workers from infectious diseases like COVID-19 — the N95 mask.
„Even fairly low-efficiency masks are actually quite effective at catching much larger particles. But, it takes a really good mask to catch the small ones as well,” said James Scott, a professor from the University of Toronto’s Dalla Lana School of Public Health who runs the lab where Marketplace’s tests were run. Neck gaiter-style masks and bandanas were among the poorest performing in the testing when it came to filtration efficiency rates, as was a two-layer, 100 per cent rayon mask. Valve masks also should be avoided if possible as they are more apt to protect the wearer, but less effective at helping control the spread of the virus.
The consumer mask Marketplace tested with an inner layer of melt-blown, non-woven polypropylene fabric and outer layers of cotton tested the best — nearly as strongly as the N95 — while blue three-ply surgical-type disposable masks also fared well in terms of filtration efficiency. With respect to cotton masks, having a mask with a higher cotton thread count (for example, 600 and 680 thread count) mattered much more in terms of filtration efficiency than whether a cotton mask had three or two layers.