If you are putting pressure in a non pressure vessel, know an explosion is a matter of “when”, not “if”
The most common mistake I see in labs (and am guilty of myself) is purposefully or accidentally turning something never meant to hold pressure into a pressure vessel.
9/10 you will end up with an extremely difficult to clean up mess, hot oil explosions, and pissed off regulators.
Pic related is what happens when you go from vacuuming a reactor type vessel to closing all the valves. The pressure from hot volatile material building up happens fast, <5 seconds. Pop goes the vessel. Luckily no one was hurt in this case.