*** This Halacha deals with topic of Yichud. Yichud is the concept that a man may not be secluded with a forbidden woman. Please read all the Halachot on this topic as there are conditions and exclusions that must be fully understood before accepting Lema’ase. ***
The work "Minchat Ish" (starting on p. 263) addresses the case of "Yichud" which involves a man who wishes to place or retrieve items to/from his safe deposit box in a bank, and a female clerk brings him into the deposit room. In many banks, the door to the safe closes and locks automatically, such that the client and the clerk find themselves secluded in the room. The "Minchat Ish" rules that their seclusion is permissible if another bank employee has the key to the room and might enter at any moment. Furthermore, if the bank has a security camera set up inside the safe deposit room, such that everything that takes place in the room is seen by somebody else, then seclusion is permissible even if nobody else has a key, since the man and woman are not truly "secluded." By the same token, if the door to the deposit box is see-through, then a man's seclusion with a woman is permissible inside the room.
If the bank operates a different security system, whereby a camera is positioned outside the safe deposit room such that those inside can see what takes place outside, then seclusion with a woman is forbidden inside the room. Even if another bank employee has a key and might enter the room, seclusion is forbidden because the man and woman inside can see through the security camera when somebody is entering the room.
Summary: A man may not enter a bank's safe deposit room alone with a female clerk unless they can be seen by those outside, either via a security camera or a see-through door, or if another bank employee has a key and can enter the room at any time.
