Abstract: Employee #1 was giving instructions to the home owner on how to work the thermostat while Employee #2 was installing insulation to the return plenum of a floor HVAC unit using a flammable duct liner adhesive. The fan came on and started an explosion and flash fire in the plenum. Employee #1 attempted to put out the fire while Employee #2 went to retrieve a water hose. Employee #1 while trying to stomp out the fire fell into the plenum and received burns over forty percent of his body. Employee #1 died of complications five days later. Employee #2 received minor burns to his arms and face and was not hospitalized. Employee #3 received minor burns to his hands and arms during the rescue attempt of Employee #1. He also was not hospitalized.