Liquid nitrogen problem - (Nov/17/2009 )
If the liquid nitrogen flask suddenly becomes almost empty i.e. containing only liquid nitrogen vapors, should it be half filled immediately or not. The temperature of both phases vary slightly so will it result in a kind of shock to the cells or there is not much difference at all.
If your tank "suddenly becomes almost empty" without reason, you should replace the tank. If it was open for a significantly long time and the LN2 is lost by evaporation...well, someone should consult the inventory before searching for vials and keep the tank covered when they are not actively removing something.
If you store your cells in the vapor phase to begin with, there is little danger. If you store in the liquid phase, there may be some loss of viability. I should think you can add 1/2 LN2 without destroying your cell cultures, as we have done this several times.
Thanks. Actually, my liquid nitrogen tank is also used as some sort of a core facility where some of my colleagues in other labs store their cell lines. As it does not have any alarm system to let us know when the level is too low, we top it up with 10-15 lit of LN2 every week. Once a colleague reported to have a very low level and we immediately filled half of it with LN2. Then there was this discussion the other day that the cells get temp. shock if this kind of thing is done....so I was thinking of having an advise from someone who has prior experience.