To provide a fire prevention system which can cope with the initial stages of a fire of a mechanical parking lot.

A change in a physical phenomenon by a fire such as a smoke or smell generated by plural vehicles in parking space 3 is positively taken in by a step direction and a column direction sampling tubes W and D and so a smoke detection device V immediately sensors a fire. A position specification device decides what column and step the parking space 3 is in. Thus, it is possible to immediately specify a position Rmn of the parking space which has a vehicle having a fire.