Abstract: The two main reasons of full surface fire for large scale crude oil tanks have been briefed. It is pointed that prevention of floating roof balance loss is the key to prevent full surface fires and the uneven distribution of rain water on the floating roof should be avoided. The difficulties of dealing with full surface fires have been analyzed and the long time burning of crude oil tanks can lead to boil over, which can lead to tank fires around the burning tanks within 5～10 diameters. To prevent the boil over of crude oil tanks is the most important target for full surface fires and it is pointed out that the crude oil tank fire should be extinguished in two hours. Three fire equipment modes have been put out for full surface fires including fixed firefighting system, mobile firefighting equipment and the combined firefighting mode.

Key words: large scale crude oil tanks, full surface fire, boil over, fire disposal