Mask required sign shows warning people that they should wear mask properly. Since covid 19 happened and it’s one of the easily spreading out disease, people always make sure to put on their mask. Wearing a mask prevents saliva from splashing on the other person and reduces the risk of infection. In particular, the role of mask sign is more important in places where many people gather, such as in public places. People who take off their uncomfortable mask unconsciously will be reminded to wear their mask if they see the signs.