What are mode of Spread of Fire ?

Fire spreads by

CONDUCTION: transfer of heat through solid body.

• — Transfer of heat through a solid body such a metals as a very good conductor of heat.
• — Since most ships are constructed by metal, heat transfer by conduction is a potential hazard.
• Fire can easily move from one compartment to another, one deck to another, and one compartment to another because of heat conduction.
• Heat is being conducted to the adjoining spaces by the metal deck and bulkhead, then the bulkhead paint is blistering (extremely hot) because vapourization has already begun.

An example of conduction:

The temperature along the rod rises because of the increased movement of molecules from the heat of the flame.