CDC report: Double-masking can block more than 90 percent of viral particles

Double-masking — specifically, wearing a surgical mask underneath a cloth mask — may provide an extremely high level of protection against the viral particles that cause Covid-19, the Centers for Disease Control and Prevention reported Wednesday.

A year into the pandemic, the report is the first from the CDC that breaks down how well certain mask-wearing techniques work to protect wearers and those around them.

"We know that masks work," said Dr. John Brooks, a medical epidemiologist at the CDC and co-author of the new report. "This is about how to help them work better."

Common surgical masks, often seen in blue, are one popular option. While these masks do a good job at protecting the wearer from large droplets — say, splashes of blood or other fluids — they're less effective against tiny viral particles, because they don't fit tightly on the wearer's face.