"mask"

Previous studies have only looked at a small selection of fabrics when the wearer is breathing normally, when particles are expelled at a lower speed.

Earlier this year, Uber built a technology designed to verify that drivers on the platform are wearing a mask while on-trip, by clicking a selfie.

The study from Simon Fraser University (SFU) in Canada, have found that mask mandates are associated with a 25 per cent or larger weekly reduction in Covid-19 cases.