Liquid Nitrogen (LN2) Safety Guidelines. Liquid Nitrogen (LN2) Safety Guidelin 1 Only trained personnel are allowed to fill 160L Dewars from the 5700L stationary tank located in the DBH loading dock "Trained personnel" refers to faculty, staff, and students who need to fill 160L Dewars on a weekly basis, have watched the liquid nitrogen safety video, AND have participated in a handson ...