Abstract: Employee #1 and Employee #2 both work as heating and air conditioning unit installers. Employee #1 and Employee #2 had installed some heating units in a community center building. The employees were purging the natural gas lines that attached to the heating units. The employees did this by opening the line and waiting for the smell of gas. When they smelled gas they would fasten the line to the heating unit. After waiting for the smell of gas on one of the units, which was taking longer than normal, one of the employees joked that maybe they should light a flame so they would know when the gas got to the unit. One of them lit a flame. There was an explosion that burned their hands and faces. Both employees received first and second degree burns and were hospitalized.