The use of two masks and making sure of a snug fit is likely to significantly reduce a person’s exposure to coronavirus, according to laboratory studies described by US health officials.

Researchers at the US CDC in January conducted experiments to see how well wearing a cloth mask over a three-ply medical procedure mask protects against COVID-19.

They also tested knotting the ear loops of a surgical mask and then tucking the excess material close to the face.

Researchers found both methods helped reduce the exposure to potentially infected aerosols by more than 90% in laboratory simulations.