A year ago I bought three one-pound cans of DuPont IMR 4227. If the cans show no sign of rust or any other type of corrosion, you should be good to go. As others mentioned, open and smell, if it smells sweet and kind of like ether alcohol, you are most likely just fine with it. When you open it, pour a bunch out and see what it looks like. If the kernals are uniform, you are most likely good to go. Be careful of any sparks when pouring any large amounts (static electricity comes to mind).