The liquid nitrogen is used to keep the freezer cold. You will then be able to place your samples inside of the freezer to preserve them. Depending on the type of samples you are trying to preserve, you can keep them cooled by liquid nitrogen for hundreds of days. Because liquid nitrogen has the potential to be dangerous, anyone who is using the freezer needs to take proper precautions to reduce the risk of injury. Caution will also help to preserve the samples and ensure there is no contamination.