My old job stored chemical waste longer than what the law allowed in containers that werent labeled correctly. No one knew for sure what the waste was because the guy that was responsible for that before me would just mix different wastes together. The solvent fridge (just a normal fridge from the 90s against a wall in the prep area out in the open) had about 10 gallons of flammable liquids (old solvents and reagents from the 400 level labs and organic classes) and 3 one liter containers of 15 year old diethyl ether which is almost certainly chock full of organic peroxides. (These are explosive) There was another container of ~100g dinitrophenylhydrazine (DNPH) in the flammables cabinet no one paid any attention to for quite some time. It was a good thing that it never became dry as that would need to be handled by the bomb squad. (Previous guy found an old crusty jar of picric acid (a friction sensitive explosive) that resulted in the bomb squad coming to the lab. That shut down part of that campus until it was dealt with) And then theres a waste container that I found at one of the outlying campuses that according to the label, had nitric acid, ammonia and bleach which is... not great.