Safety cans hold flammable liquids, combustible waste, acids and corrosives and prevent accidents and fires. They have either a single opening or one opening for filling and a second opening for pouring. The second opening typically has a flexible metal hose to increase pouring accuracy. Some safety cans also have roll bars to protect contents during transportation. Safety cans come in three main types. The standard safety can holds flammable liquids. Oily waste safety cans hold combustible waste such as solvent-soaked rags. High-density polyethylene (HDPE) safety cans hold acids and corrosives.