Introduction : Underground structures are characterised by the fact that their outer walls are tightly joined to the soil. Those being deeper than one floor beneath the ground normally have neither celler windows nor outside of the use of the vertical passages such as stairways and elevators. The inaccessibility of underground structures due to smoke generation in the event of fire results in some unique problems and difficulties. Primary among these are: a) Difficulty in venting smoke, heat and toxic products of combustion. b) Difficulty in fire fighting and evacuating occupants. c) Difficulty in making any appraisal of the fire conditions or about whereabouts of the fire itself. d) Difficulty in communication between personnel below ground and also between persons on the surface and below ground. e) Difficulty in effectively applying extinguishing media. f) Unusual congestion and restriction of movement in the interior of the underground...