happy, healthy 9-month-old when she developed cold symptoms that wouldn't go away. >> they said it was probably croup. it was very common. but it never got better. we ended up bringing her to the emergency room. they said, go home, it's going to take time for it to go away. >> reporter: but it didn't go away. later that night at home, hazel stopped breathing. her mother took her back to the e.r. >> they did an x-ray at that point and saw what they thought was a nickel lodged in her esophagus. >> reporter: now in grave condition, doctors examined her x-ray more closely. they realized it wasn't a nickel but a battery. >> the corrosive nature can begin to cause problems in the tissue within 2 to 2 1/2 hours. >> reporter: they're in common, everyday objects all around you. simple, round, so-called button batteries made of lithium. when they're accidentally ingested by a young child, it can be deadly. when a lithium battery becomes lodged in the body, it gives off an electrical current which reacts with surrounding tissue, producing a strong acid similar to a household drain opener.