If you purchase and use 100 gallons of solvents a month to clean your machine, you know that you have generated spent solvent which in most instances is a hazardous waste. This is your “generator’s knowledge”. You do NOT need to analyze your spent solvent to show that it is hazardous. Based on your knowledge of how you use your material, you have the knowledge to determine that it is hazardous.
On the other hand, if you find 5 drums of unknown chemicals sitting in your warehouse and no one can tell you where they came from. You have NO generator’s knowledge and you must conduct chemical analysis to determine if these drums contain hazardous waste.