CFR / 
Title 41
 / Part 102-80
 / 
Sec. 102-80.145 What is meant by ``flashover''?
Flashover means fire conditions in a confined area where the upper gas layer temperature reaches 600 [deg]C (1100 [deg]F) and the heat flux at floor level exceeds 20 kW/m2 (1.8 Btu/ft2/sec).