Oh, I have a story about LN as well. I studied nuclear engineering in school and our department had a nuclear reactor in the building (important in a moment). Nuclear engineering labs usually have large LN tanks because some types of radiation detector require cryogenic cooling. One day of the week at about 3AM some [presumably students living on campus[ were walking by and heard the tanks venting exactly as you mentioned. They called it in to campus security, who panicked and assumed the reactor was melting down (not even possible with this reactor) and by 3:30 AM a full emergency response crew, in full HAZMAT gear and complete with heavy vehicles has surrounded the building only to discover that nothing is remotely wrong.