"Between five and 10 times a day, an arc flash explosion occurs in electric equipment somewhere in the United States that sends a burn victim to a special burn center, according to statistics compiled by CapSchell, Inc., a Chicago-based research and consulting firm that specializes in preventing workplace injuries and deaths.
That number does not include cases sent to regular hospitals and clinics, or unreported cases and “near misses,” estimated to be many times that number. There are one or two deaths a day from these multi-trauma events, noted Dr. Mary Capelli-Schellpfeffer, principal investigator.

The above quote is from an article in Maintenance Technology magazine titled "The Dangers of Arc Flash Incidents".