Employees were performing well pad completion work. They pumped nitrogen into the well unit to open it up so that it would flow/produce. The employee went to the sand-removing unit/trailer to check if the well was flowing. He was standing on the steps and walkway of the trailer when an explosion occurred that knocked him over the walkway handrail resulting in a 3-4 foot fall. He was hospitalized with a fractured left foot and first-degree burns to his hands. A generator about 37 feet away had caused the ignition.