In many customer facing and security roles, a mask is not appropriate. In these circumstances shield (or visors) might replace masks as a more comfortable and more effective deterrent to COVID-19.
Shields have a number of advantages over masks: first of all, they are endlessly reusable, simply requiring cleaning with soap and water or common disinfectants; secondly, shields are usually more comfortable to wear than masks, and they form a barrier that keeps people from easily touching their own faces
When speaking, people sometimes pull down a mask to make things easier—but that isn't necessary with a face shield. The use of a face shield is also a reminder to maintain social distancing, but allows visibility of facial expressions and lip movements for speech perception