Canada's top public health doctor now recommends 3-layer non-medical masks

The Public Health Agency of Canada is now recommending Canadians choose three-layer non-medical masks with a filter layer to prevent the spread of COVID-19 as they prepare to spend more time indoors over the winter.

Chief Public Health Officer Dr. Theresa Tam made the recommendation during her bi-weekly pandemic briefing in Ottawa Tuesday.

"To improve the level of protection that can be provided by non-medical masks or face coverings, we are recommending that you consider a three-layer nonmedical mask," she said.

According to recently updated guidelines, two layers of the mask should be made of a tightly woven fabric, such as cotton or linen, and the middle layer should be a filter-type fabric, such as non-woven polypropylene fabric.

"We're not necessarily saying just throw out everything that you have," Tam told reporters, suggesting adding a filter can help with protection.

The Public Health website now includes instructions for making three-layer masks.

The World Health Organization has recommended three layers for non-medical masks since June. When pressed about the sudden change for Canada, Tam said the research has evolved.

Watch: Dr. Tam suggests using three-layer masks with filters as we move indoors https://www.cbc.ca/player/play/1815052867817/

"This is an additional recommendation just to add another layer of protection. The science of masks has really accelerated during this particular pandemic. So we're just learning again as we go," she said.

"I do think that because it's winter, because we're all going inside, we're learning more about droplets and aerosols."

She also urged Canadians to wear well-fitted masks that cover the nose, mouth and chin without leaving gaps.