You need to treat this stuff with respect. First, because it will freeze your flesh solid in mere moments. Second, if you aren’t careful, you might condense liquid oxygen in your trap. This is considered a Bad Thing, as solvent and liquid oxygen tend to go BOOM when they warm up. But we usually only gave cursory attention to the inherent explosive power of liquid nitrogen when it warms up. Mainly because no one was ever stupid enough to put liquid nitrogen in any kind of a sealed system.
Well, in this blog post, Derek Lowe describes an incident involving a sealed liquid nitrogen tank at Texas A&M. If you ever worked in a lab environment, this will leave you shaking your head.
I am SO glad I survived grad school.