What happened?:
A trap was left up overnight to dry solids. It was properly insulated and topped off with liquid N2, but I did not wait for the vacuum to go down before leaving. It turns out the seal was not good and I condensed liquid O2 overnight. In the morning, when the vacuum gauge was still at 1 atm, I realized the mistake and removed the reduced pressure and let the O2 boil off before disturbing the trap. Nothing exploded.