Abstract: At approximately 10:30 a.m. on May 11, 1989, Employee #1, an electrician, was helping another electrician try to start a gas-fired furnace. Several attempts were made to light the furnace, which was controlled by an external electrical control panel, by going through normal operating procedures, but the furnace would not remain lit. Employee #1 went to the end of the furnace and looked through an inspection sight glass. At the same time, the other electrician let the furnace go through the purge cycle, then used a jumper wire to bypass the electrical relays in the control box in an attempt to keep the burner lit. When the ignition button was pressed, the furnace exploded. Employee #1 sustained no physical injuries, but apparently suffered from a concussion and shock. He was transported by automobile to the hospital, where he was treated and released. The other employee sustained no injuries.