'Mask Hacks' study suggests effective alternatives to N95s


Research by a University of Windsor scientist suggests wearing a two-ply cotton mask fastened tightly with ties over a basic medical mask offers similar protection as wearing an N95 mask.

In his ongoing research related to COVID-19 and its variants, School of the Environment professor Ken Drouillard, is participating in a “mask hacks” study by a team at McMaster University led by researcher Catherine Clase.

The study involved testing various masks, and combinations of masks and mask-wearing devices, to find those with the best performance ability to filter out aerosol-sized particles.

“This is timely information for the public,” said Drouillard. “Given the high community risk factors posed by the Omicron variant and the scarcity of N95 masks in some provinces, we want to be able to help people use the best mask they have access to.”

Drouillard’s spouse, Rebecca Rudman, is one of the founders of the Windsor-Essex Sewing Force. The group of community volunteers has produced tens of thousands of cloth masks donated to frontline workers and vulnerable populations.

Drouillard has lent his expertise to the project and has recruited other UWindsor scientists to perform tests on various mask designs and fabrics to ensure the volunteers could produce the most effective masks possible.

Drouillard and the McMaster team performed tests on masks used in combination with those produced by the local group of sewing volunteers. Using a TSI portacounter— the same device used for fit-testing N95 masks— they tested the concept of “double-masking”— wearing two masks at a time.

He said the most effective was wearing a two-ply, pleated cotton mask with cotton straps tied snugly over a standard medical mask.

Not all medical masks are created equal, Drouillard explained.

True medical-grade masks are certified by ASTM, an international standards organization. Certified ASTM masks bear the organization’s name on the box. There are three grades of masks available, the L1 being the cheapest and most accessible. The higher grades relate to the mask’s ability to prevent fluids from soaking into them and are generally used only in hospital settings, Drouillard explained.

Research testing results:

  • -Drouillard’s testing has shown an L1 alone, worn snugly on the face, filtered out 54 per cent of particles. -A two-ply, pleated mask made of high-quality quilting cotton and with ties rather than ear loops provided 55 per cent effectiveness.
  • -In combination, with the cloth mask with ties worn over the L1, the filtration rate was nearly 91 per cent.
  • -Drouillard said that with double masking, it is the medical mask underneath that is doing most of the aerosol filtering. The cotton mask with ties mainly acts to improve the fit of the medical mask underneath. This prevents leakage from the medical mask which can be as high as 50 per cent when worn alone.
  • Drouillard said testing has shown the two-ply cotton masks can be washed dozens and dozens of times without affecting their performance.
  • -When wearing a mask brace, a contraption made of silicone straps you wear around your head over a mask, worn over an L1 medical mask has a filtration rate of 82 per cent.
  • -Masks made of quilting cotton with strings that tie around the back of your head are 55 per cent effective in filtering out particles because they fit more snugly.
  • -The same cotton mask with ear loops is only 50 per cent effective in filtering out particles because it has more leaks than the one with ties, Drouillard said.