A safety valve releases a fluid in the event of a fire. To do so it comprises a valve shutter in a body for opening or closing a pipe containing the fluid. A first spring is kept under tension against heat-sensitive means for releasing the valve shutter when the tension is released by the sensitive means. The sensitive means comprise a piston acting on the first spring, a pipe being connected to a chamber delimited in the body by the piston on the opposite side to the first spring. The pipe and the chamber contain a pressurized control fluid so that the piston keeps the first spring under tension. The pipe is made of a material capable of melting at a predetermined temperature so as to release the fluid in the event of a fire around the pipe.