I work in a building which is shared between two companies and the majority of workers of the other company smoke. What bothers me is that they smoke in a room inside the building which we share. We have no access to the room and it is their rest area not a designated smoking room. They have the door closed (most of the time) but when the door is opened afterwards the smell from the cigarettes spreads to my office. Is this legal and if not who should I report them to ?