How do I determine whether a chemical waste is "hazardous" or "extremely hazardous"?

"Handling and Disposal requirements are different for hazardous and extremely hazardous chemical waste.
Check the list of Known Hazardous and Extremely Hazardous Wastes for your material here: ucsd.edu/safety/research-lab/hazardous-waste/disposal-guidance/extremely

Is Chemical waste always considered hazardous?
Chemical waste is largely composed of harmful chemicals. This does not mean, however, that it is classified as hazardous.

For it to be considered hazardous, it must have an ignitability, corrosivity, reactivity or toxicity characteristic, according to the U.S. Environmental Protection Agency.