When John Steffen died, his family had little doubt that a lifetime of cigarette smoking was to blame. Then, the Nebraska Department of Health got an unusual tip. Today, we begin a two-part series on the promise and the peril of vaping. Guest: Julie Bosman, a national correspondent for The New York Times, spoke with Kathleen Fimple and her daughter, Dulcia Steffen, in Omaha, Nebraska. For more information on today’s episode, visit nytimes.com/thedaily.  Background reading: John Steffen trusted vaping could help him quit smoking. Instead, he became one of vaping’s first victims in Nebraska. Vaping can cause lung damage resembling toxic chemical burns, according to researchers at the Mayo Clinic.