Question:
As part of my job, I will probably have to clean out a basement together with another intern, who is female, which presents a shaila of yichud. There are other people in the actual building, but in terms of the basement, it will be only the two of us. May I rely on telling the goyishe security guard to check in on us from time to time? May I rely on leaving the door open or unlocked, even though no one will actually come in, unless I request, and even then who knows if the goy will want to come in?
Answer:
The best thing is to keep the door open and request one of the Jewish neighbors to drop in unexpectedly.
Sources:
E:H 22:5 & 9, 148:2 Ramo, Pischei Teshuvah E:H 178:15, Makneh Kiddushin 91, Teshuvas Maharil Diskin Kuntras Acharon 206, Teshuvas Dovev Meshorim 5,
