In a typical kitchen there might be several cooks or chefs to that help prepare each dish. With each of those dishes being exposed from all of the cooks, it may be quite unsanitary. Anything that comes out of their mouth, including diseases and germs fall and will eventually make it to the ground. In some cases, it will land on the table or the food the cook is preparing. In worst case scenarios, the cook may choose to work while sick during their shift or possibly may be working without knowing he/she is sick.
According to the Food Safety News blog site, "ROC’s report, “Serving While Sick,” also found that 63 percent of workers reported cooking or serving food while sick at some point."https://www.foodsafetynews.com/2014/09/california-to-require-paid-sick-time-for-restaurant-workers-and-others/?fbclid=IwAR2e9pn2IrWrnFOq8o-y1d36Loha0cWVuJsp2pCiuaNbx4Cn0AtxEpP_Dnk
Now this is definitely a case for concern and some measures to avoid the spread of disease and germs should be met. Even if the worker covers their mouth during a sneeze or a cough, the air that they breath is still a concern. This is because the air he or she exhales will make its way down to the food or table which obviously carries the germs or disease.
The most common type of mouth mask is the ones you see nurses or doctors wearing at the hospital, but now there are mouth shield masks specifically designed for food service workers. Shield of Glory's mouth mask is an open mask that prevents germs/disease from getting onto the food or surrounding of their worker's environment.