“if a situation should be avoided because of yichud, it doesn’t matter if it’s thirty seconds or thiry minutes!”
Please check your school notes, it does make a difrence. There is a time frame for yichud and in an elevaitor that could be open from the outside by people pushing the button on any floor there is no yichud.
“therealmgama, Is there a problem with going on an elevator in a business building? “
besides the above rerason for not being yichud an elevaitor in an office building usealy has a security camara.