Well I had to go to the medical centre yesterday. No-one is allowed into the building not wearing a mask. They gave me one at the door. At the end of my visit I asked the senior practice nurse whether I could use the same mask again when I go next week. She said I could as long as I didn't get it wet (she didn't specify what kind of wet). Then she said that whatever I do I mustn't put my fingers behind the mask whilst wearing it. She demonstrated to me what she meant by sticking her fingers behind her mask. :-)